Xantia V6 broken exhaust (update: and rough low rpm running)

[Hell Razor5543]

I don't know if this helps, but when my mum finished servicing her BMC engine (she lives on a narrow boat, and was a car apprentice some years ago), she found orange handwash got rid of the smell of diesel (and nothing else she had tried did). She found that the one that worked best was named after cowhide with expansionist tendancies.

[addo]

Fat Fresian?

[CitroJim]

was named after cowhide with expansionist tendancies.

That's got me...

Imperial Leather?

[Hell Razor5543]

That's them!

I've used it as well, and the Orange handwash does shift the smell of diesel (and some other smells as well). The downside is that your hands smell of orange instead!

I don't know if it would work on stenching agent, but if it does it would be worth knowing.

[Mandrake]

Quick update.

Changed the gearbox oil today. Not a difficult or scary job at all, much the same as the 4HP14 except for checking the temperature with the Lexia and having to remove the air filter housing to get at the dipstick.

Went for a drive to get the gearbox oil up to 80 degrees, came back, measured the oil level with the engine idling, found it was well below the bottom mark, in fact it was only just covering the M on the word minimum, eg about 2-3 millimetres up the bottom of the dipstick. Given that its half a litre between the low and high marks it was approximately half a litre below the lower mark.

Drained it with the front up on ramps, only got 3.2 litres out probably because the level was low to begin with. The old oil is completely opaque and somewhere between dark brown and black. It doesn't smell burnt, but then again new LT71141 doesn't have a bad smell to me either so I may not be the best person to judge the smell! I did see a few specs of dirt in the catchment tray (that could have been from the outside of the gearbox near the drain plug) but nothing serious, the oil just looks really dirty, but no real evidence of any particulate matter like clutch breakup.

I ended up having to put back about 3.9 litres to get the level half way between the marks while idling at 80 degrees, so it now has 0.7 litres more oil in it than before...

It doesn't seem to have made much if any difference to be honest but I've only driven a few miles so it may be too early to tell as the oil won't have had a good chance to fully mix with the old stuff... I also checked the banjo - no obvious sign of a leak, although its hard to tell as the entire side of the gearbox including the banjo is caked in muck, probably a mixture of oil and dirt. The banjo pipe, at least the parts not caked in muck looks quite rusty with a bright orange rust appearance...

I also thought it was time to reconnect the oxygen sensor - big mistake, engine performance has dropped away quite a bit again. In fact the low down engine performance is very flat and unimpressive even for a 4 cylinder let alone a 6, so there is no doubt that there is a significant loss of power low down.

One other follow up on the coolant saga at Richards - after coming back from the drive I used to warm the gearbox oil I had my head under the bonnet just as the coolant expansion tank let off a 10 second long "psssssssssssst!!" together with a fine mist spray of coolant. I couldn't tell whether it was the seam of the expansion tank leaking or whether it was the pressure cap letting some pressure out.

Why would it do that ? Thinking dangerous thoughts aloud here, but is there any possibility that my loss of power could be a head gasket on the way out ? And that the pressure relief was due to the coolant being pressurised by head gasket blow by ? Other thoughts along similar lines - a major source of damage to oxygen sensors is apparently coolant contamination due to a blown head gasket, the lambdapower website recommends that an oxygen sensor almost always needs replacing after repairing a blown head gasket... and then there is the fact that there is a LOT of moisture in the exhaust at times, but not all the time...some coolant being combusted perhaps ? It does use about half a litre of coolant every 2 months or so. Maybe I'm just paranoid.

Off to visit Lexi tomorrow to have a look at the spark plugs. My gut feeling is we won't find anything too wrong with them, but it needs to be ruled out, along with the fuel rail regulation hose...

[CitroJim]

Well done on the gearbox oil change Simon.

Yes, you're being parnoid on the coolant. All V6s use that much - it's what they do and when they (rarely) let head gaskets go the result is spectacular. Ask Chris570...

I'll wager your expansion tank has a tiny split at the seam - they do it for a pastime. Can you see any traces of crystallised coolant below it?

With the oxygen sensor connected what output do you see from it on the Lexia?

[Mandrake]

Yes, you're being parnoid on the coolant. All V6s use that much - it's what they do and when they (rarely) let head gaskets go the result is spectacular. Ask Chris570...

So where does the coolant go ? My 2 litre never seemed to use any. Richard checked the bottom of the heater matrix for drips when I was there and didn't find anything so despite a curry smell I don't think there is any significant leakage on the heater matrix either.

Nothing wrong with being paranoid - just because you're paranoid doesn't mean they aren't out to get you

I'll wager your expansion tank has a tiny split at the seam - they do it for a pastime. Can you see any traces of crystallised coolant below it?

Yes I've mentioned before that it has white stains below the seam, so I guess it could have a leak that only occurs under full pressure. First time I've actually observed it happen though, and I couldn't see where it was coming from as it was coming from the back, and bearing in mind that the radiator cap release hole is at the back too... What pressure does the radiator cap normally vent at ?

With the oxygen sensor connected what output do you see from it on the Lexia?

Oxygen sensor output is normal - varying back and forth from around 80mv to 800mv or so, although it does seem quite slow, as it can take nearly 2 seconds for one cycle, although sometimes it does speed up a bit.

Power is definitely down on what it was with the sensor disconnected (flat as a pancake springs to mind) but it wasn't pulling that well with it disconnected either. It was just less bad... Still no clear idea what's going on here, lets hope tomorrows expedition into the rear spark plug bank will provide some illumination...

[CitroJim]

Pass, only I know it goes somewhere! I've had three and they've all done it and yes, my 2.0 TCTs don't use a drop...

It very much sounds like your expansion tank Simon... I reckon they all leak to a greater or lesser extent - even from new...

Cap vents at 15psi. (1 of those bar things). A normally driven V6 does not need to be pressurised and a trick when the tank is a bit weak is to run with the cap half-undone so no pressure builds. It works...

Umm. That's more or less normal for a sensor. What you need to do is pop along to your MOT man and have him do an emissions test and see what lambda his machine reads. It'll tell you if yours is doing a good job or not. Basically if his machine reckons lambda is within limits and the car is under the limit for CO and HC then all is hunky-dory.

In fact an emissions test might be very revealing as the combination of lambda, HC and CO at natural and fast idle as well as it 2500 rpm can be very revealing. Now it'll be more accurate with the exhaust repaired. From what you get from that it might give us a valuable clue... It needs to be a fresh one and not your last MOT one...

[Mandrake]

A big update for all those patiently waiting for the next chapter in the V6 saga.

Firstly a big thank you to lexi for letting me use his car port yesterday to do the rear spark plugs, it was certainly nice to do the job without the ever present fear of the heavens opening up on me...and also for donating the inlet manifold gasket that he had bought for the car last year but had never got around to using before he sold me the car. It was good to catch up and say hi again too.

Naturally when we took the car for a quick test drive before doing the work it would barely play up, at least it wasn't making the groaning noise much. So what did we find ?

Well the spark plugs were NOT oiled at all, all were dry. Yes there is a significant oil leak from the right hand end of the rear camshaft cover and the pocket in the head for that spark plug was fairly full of oil, in fact it wasn't too far from the top of the spark plug tube, however it had not leaked into the spark plug tube, in fact the spark plug was dry and rather rusty. Why that one spark plug was rusty and the others weren't I don't know. (I mean the outside of the plug on the hex, not the electrode end)

There was a small leak into the middle rear spark plug pocket (but not into the tube either) and nothing of significance on the left hand one.

Yes the leak needs dealing with at some point but its not major, its done at least 3000 miles over a couple of years to leak maybe 20ml of oil to come up near the top of the tube, so I've just cleaned out the oil and will close my eyes to this problem until next spring... The important point is the plugs were not oiled, and it has new plugs fitted now. (I'm still interested in hearing whats involved to do this job though so I can plan ahead)

Along the way I found two major problems. Problem number one was that when I removed the inlet manifold I was searching for the old gasket only to discover that there wasn't one fitted. Yes, no gasket, just what was left of a thin layer of some sort of blue coloured silicon like sealant. Looking at the patchy scraps of what sealant was left I'm almost certain that there must have been air leaks at the inlet manifold, so there is a potential lean running problem right there as that air is not being measured by the ECU, not to mention that it would also upset the resonance tuning of the air intake manifold...this is the sort of problem that could easily have got worse over the last few months, as I've already done double the milage that lexi did in the car. The sealant probably fell apart and disappeared with the long trips I've done...

I wasn't sure whether the gasket (some sort of cardboard material) needed any grease or sealant, so I fitted it dry. (what is the recommendation ? ) It probably needs to come off again soon anyway, see below.

Problem number two is that the rear spark plug leads are faulty. Jim, are you sure that they are copper wire and not carbon resistance leads ? Two of them are broken (internally, not visibly) between where they exit from the plastic housing and the curved plastic guide - the cable has to be held in a fairly particular position to get any reading at all on those two, any other angle and two of them go completely open circuit.

All three read between 4k and 6k when held in a position to work, which is what makes me think they are resistance leads, as its hard to believe all three would have about the same resistance if they were just faulty copper leads...

Now of course a break in the spark plug leads is not going to cause a complete loss of spark as its just a tiny additional gap for the spark to jump, but it will weaken the spark potentially causing a misfire under load, and the fact that two of the six cylinders have an intermittently weak spark is going to upset the balance of the engine and cause vibration under load, so I think this is a big part of my low RPM roughness and vibration.

So looks like I need new rear spark plug leads. If I was doing the job at home I would have left the car off the road for a few days to order new leads and fit them before reassembly but as I was at lexi's I had to put them back in as is so I could vacate his car port and get home again...which means lifting the manifold off again and another manifold gasket...

However now I've done the job once I'm pretty confident I can manage it on my own given a sunny day, I reckon I could do it in half the time now, especially if I'm just lifting it to put new plug leads in and not touching anything else like spark plugs.

One more thing I noticed is the secondary air hose going into the back of the air filter box on the right hand side - when I first started the engine after putting all the manifold back in but with the air filter still removed there was a hell of a sucking noise which at first sounded like a dry bearing but was in fact just sucking from that smaller hose. I've run the engine with the air filter box off many times before and NEVER noticed a loud, powerful suction from that hose...(easily as strong as a vacuum cleaner at idle...)

The amount of suction from that hose also seems to change with engine revs in an abrupt fashion as if there is some sort of solenoid operating to block and open the flow ? Can someone explain to me the purpose of that pipe and what it is connected to ? Is it possible that the vacuum from the inlet manifold was much lower than it should have been due to the missing inlet manifold gasket, and that now that I've fixed that leak the suction is much better ?

I also discovered that there was supposed to be a hose clamp on that hose where it pushes onto the air filter box - I've never seen one on there since I've had the car and assumed it was just a push fit, but discovered it had slid down the pipe out of view. As it was a crimp type that I couldn't re-use I've put a big jubilee clip on it so now it will be sealing for the first time since I've had the car.

BTW I also checked the small air line from the inlet manifold to the fuel regulator - it was tight and looks in perfect condition, so I don't think theres any problem there.

So how does the car run now after this work, considering that I had to put the faulty plug leads back in ? MUCH more power, but by no means fixed. Especially when cold its now much more responsive on the throttle, almost as good as it was when I first got it, so overall a big improvement, it does look like the manifold leak is a major part of the "flat" performance its had lately. Meanwhile I think the intermittent plug leads could be responsible for the roughness and shudder at low RPM.

On the trip back from lexi's last night the performance on the motorway was FAR better than its been for a long time, almost no complaints. Tonight I dropped my GF off at a friends - on the trip on the way out there while the car was fairly cold it ran very well, very responsive off the mark with light throttle, pulling fairly well at low RPM but by the time I was driving home it had deteriorated a lot and become a bit more sluggish and cantankerous, in particular it was actually "shuddering" when trying to pull at low revs as if the engine mounts were worn out, or similar to what you might notice on a manual with an oil leak on the clutch... I'm wondering if the two faulty plug leads were working for a while then went open circuit through heat expansion ? It certainly did feel a bit like a misfire when it was shuddering...

The gearbox is a mixed bag, it does seem very intermittent as to whether it will groan or misbehave or not. I've now done about 50 miles since the oil change, when trying to demonstrate the problem to lexi it would hardly play up at all, on the way home from lexi's the gearbox was mostly well behaved, tonight when cold it was almost normal but after it warmed up it started doing weird shifts and changing back and forth to limited slip... in particular I notice that if you're cruising at about 2000rpm and you accelerate a bit at first there is some limited slip that allows the engine revs to lift and then it cuts in the full lock up and you can feel it go solid as the revs drop again.

Ease off on the throttle a bit and then apply throttle again and it will do the same thing - limited slip until the revs rise a bit then it will cut back to full lock up. I don't recall this behaviour a few months ago before the groaning started so the jury is still out on the gearbox.

One other thing, I first noticed it at lexi's yesterday but I sometimes hear a small whine that changes with engine revs, only really noticeable between idle and about 1500rpm, which sounds exactly like alternator whine...but I can't seem to confirm if it is the alternator or not. Seems odd that I would notice it the first time a day after changing the gearbox oil. Please don't let it be the oil pump in the gearbox...

So the next step I guess is to get some spark plug leads and another manifold gasket, as well as do a second change of gearbox oil. I've found a set of leads for £72 here:

http://www.ignitioncarparts.co.uk/Parts ... ON%20LEADS" onclick="window.open(this.href);return false;

Does anyone know if I can do any better than that ?

At last I feel like I'm making some progress, but I'm still very worried about the gearbox...

[CitroJim]

Well, that's excellent Simon That missing inlet manifold gasket is not going to help at all...

No, I can definitely confirm the plug leads should be solid copper and not resistance. The plugs are resistor plugs so the leads don't need to be. I resistance checked the leads on pavlosv6's car myself and they are straight but to really get a good reading it was necessary to remove them from the plug connectors on the rear bank (the dummy coil) and clean up their ends.

Yours look duff it you have to hold them in a given position to see anything at all.

Next thing I'd change the coolant temperature sensor as this is now suspect if the car is OK when cold.

The second pipe from the airbox carries the idle air via the idle control valve to the inlet manifold. At idle the main butterfly is closed and all air goes via the idle control valve. It does suck very hard and is initially very noisy when disconnected from the airbox. At normal running temperature considerably less air is needed and it goes quiet(er). What you hear there is all quite normal.

Simon, automatic gearboxes make a heck of a racket in perfectly normal operation. A kind of 'white noise'. Just drive a manual V6 and hear the silence!!! It is an education and a revalation. Therefore I think you are worrying totally unnecessarily Just think of what's going on in the gearbox. All that fluid sloshing around at high pressure is not going to be exactly silent.

Believe me, when an HP20 is getting ready to throw its toys it really starts to scream - not a gentle whine like an alternator whine but an all-out banshee wail...

You're getting there

[Mandrake]

No, I can definitely confirm the plug leads should be solid copper and not resistance. The plugs are resistor plugs so the leads don't need to be. I resistance checked the leads on pavlosv6's car myself and they are straight but to really get a good reading it was necessary to remove them from the plug connectors on the rear bank (the dummy coil) and clean up their ends.

Yours look duff it you have to hold them in a given position to see anything at all.

Is there no possibility that different revisions of the engine have copper or resistance leads ? If not I guess they are well and truly faulty, which could explain a lot. Yes, I pulled the plug connectors right off the dummy coil assembly so I was measuring directly to the flat copper disc in the hole, and I gave both ends plenty of scratching with the multimeter probes to get a good contact, there was no doubt at all, one lead was 6k and didn't change with bending of the cables, the other two were about 4-5k when held "just so" but were open circuit for most angles of bending, and it seemed to be somewhere close to where the cable exited the dummy coil assembly that the breaks were present.

I've never heard of resistor plugs before, do you mean there is a carbon resistance between each end of the spark plug ?

Next thing I'd change the coolant temperature sensor as this is now suspect if the car is OK when cold.

Yes I was beginning to wonder about that too, it does always seem to run better cold and gets more cantankerous when its gets hotter, although there are a lot of other potential suspects too...when hot the temperature reported by the Lexia from the coolant sensor is anywhere between 10-15 degrees higher than the temperature gauge on the dash - I assumed that it would be the dash sensor that was in error but maybe not. When fully warmed up I sometimes see a reading as high as 98 degrees on the Lexia but only about 85 - 90 on the dash readout.

On the other hand if it really is reaching 98 degrees that could explain the expansion bottle leaking! Maybe its due a thermostat too... sigh... (on the other hand if the dashboard temperature sensor is the one thats correct the temperature is fine)

The coolant sensor is the green one on the coolant line on the right hand side of the engine heading to the radiator that is easy to access with the air filter box removed is it ?

The second pipe from the airbox carries the idle air via the idle control valve to the inlet manifold. At idle the main butterfly is closed and all air goes via the idle control valve. It does suck very hard and is initially very noisy when disconnected from the airbox. At normal running temperature considerably less air is needed and it goes quiet(er). What you hear there is all quite normal.

Ah, gotcha. I was looking at the butterfly wondering where the idle air passed through, that explains things. Yes you're right the suction was very loud and strong when first started but dropped when I opened the throttle, and also died a way quite a bit over a few minutes at idle. The thing is it has never been this loud (never audible at idle) or had as much suction before, which I attribute to fixing the inlet manifold gasket.

Simon, automatic gearboxes make a heck of a racket in perfectly normal operation. A kind of 'white noise'. Just drive a manual V6 and hear the silence!!! It is an education and a revalation. Therefore I think you are worrying totally unnecessarily Just think of what's going on in the gearbox. All that fluid sloshing around at high pressure is not going to be exactly silent.

I know, but then there is a loud groan that passes right through the floor into your feet, and the erratic torque converter lock/unlock and erratic gear shifts that are worrying me, I know autos are a bit noisy in general... my HP14 was quite noisy in 3rd at low revs too...

Believe me, when an HP20 is getting ready to throw its toys it really starts to scream - not a gentle whine like an alternator whine but an all-out banshee wail...

Ok, well hopefully a whine wont turn into a banshee wail then...

You're getting there

Yep, for sure, it will be interesting to see what difference the plug leads will make. I'd say a lot.

[DickieG]

Now of course a break in the spark plug leads is not going to cause a complete loss of spark as its just a tiny additional gap for the spark to jump, but it will weaken the spark potentially causing a misfire under load

That's not entirely true Simon, in fact quite the opposite as a coil will produce a higher voltage/larger spark in those circumstances in order to bridge the gap. Many years ago just after I left school I worked in a Ford dealership selling new cars and a regular problem was new cars having a misfire due to plugs getting fouled up due to manual chokes causing over rich mixtures, anyway an old sage mechanic showed me a trick of just lifting the plug leads away from the plugs by a few mm would cure the misfiring cylinders and the engine would now run smoothly. Several years later when I had my own Crypton (Sun) tuner I explored the old sages trick and low and behold when a plug lead was lifted away from the plug the firing voltage rose significantly on the cylinders where I'd lifted the HT away from the plug giving a stronger spark.

As you suspect that you have a faulty HT lead have you tried the old school trick of parking the car nose into a completely dark garage/area then running the engine whilst observing for traces of arcing? In order to induce arcing, regularly blip the throttle as accleration causes the coil to produce a higher voltage and will expose faulty insulation on the HT leads.

So looks like I need new rear spark plug leads. If I was doing the job at home I would have left the car off the road for a few days to order new leads and fit them before reassembly but as I was at lexi's I had to put them back in as is so I could vacate his car port and get home again...which means lifting the manifold off again and another manifold gasket...

New gaskets are only a couple of quid.

One more thing I noticed is the secondary air hose going into the back of the air filter box on the right hand side - when I first started the engine after putting all the manifold back in but with the air filter still removed there was a hell of a sucking noise which at first sounded like a dry bearing but was in fact just sucking from that smaller hose. I've run the engine with the air filter box off many times before and NEVER noticed a loud, powerful suction from that hose...(easily as strong as a vacuum cleaner at idle...)

The amount of suction from that hose also seems to change with engine revs in an abrupt fashion as if there is some sort of solenoid operating to block and open the flow ? Can someone explain to me the purpose of that pipe and what it is connected to?

The suction noise is from the idle control valve = normal.

[DickieG]

when hot the temperature reported by the Lexia from the coolant sensor is anywhere between 10-15 degrees higher than the temperature gauge on the dash - I assumed that it would be the dash sensor that was in error but maybe not. When fully warmed up I sometimes see a reading as high as 98 degrees on the Lexia but only about 85 - 90 on the dash readout.

Saw the same thing on my V6 (now Jim's)

[CitroJim]

Resistor plugs are almost the norm these days Simon.

In NGK nomenclature the 'R' in the part number stands for resistor. So, for instance a BKR6EK is a resistor plug whereas a BK6EK is not...

You can decode the other bits of an NGK plug part number if you are bored enough...

The temperature reading compared to Lexia and the gauge: As I may have said before the sensors are effectively in different places; the CTS (green) is in the top hose effectively whereas the gauge driver (Blue) is effectively in the bottom hose so you will see the CTS often reading a higher value than the gauge.

Don't even think about diagnosing the gearbox until the engine is sorted Simon

[xantia_v6]

A few quick comments on no particular order:

The trick of clearing a fouled plug by holding the cap off the plug by a few mm works because the waveform is different, not because the voltage is higher. The voltage (at the plug) with a spark jumping from the lead to the plug has a very fast rise-time compared with the rise time from the coil alone, and the high frequency components tend to prefer jumping the electrodes to taking the resistive path. Note that old fashioned distributors had a built-in spark gap between the end of the rotor and the electrodes on the cap, but the effectiveness of that is diminished by the length of spark plug lead (especially resistive).

The V6 ECU calculates airflow from manifold pressure and a known volumetric efficiency curve, not by measuring the air flow. This means that an air leak into the manifold is (on average) correctly compensated by the ECU. If the air leak is in or near the runner to a particular cylinder, then that cylinder may run a little lean, and the others a little rich, but only to the extent that the manifold prevents redistribution of air between the cylinders.

I think that you may be a little confused (or maybe I am) with your description of limited slip and full lock-up of the torque converter. My recollection is that it only has two states, locked (with limited slip) and unlocked. It is never locked solid. It is normal for the converter to be unlocked by small increases of throttle opening while cruising, the locking and unlocking should only be detectable by observing the tachometer and (if you have and after-market exhaust) the engine note, you should not feel it.

I don't think that my previous V6 ever used water, other than that leaking from the seams of the 3 expansion tanks I had fitted. If you let the level drop a few mm below the seam, then it would use none at all.

In NZ, (at least until the 90s) resistor plugs were almost unheard of. From the early 60s, import protection controls meant that you could only buy spark plugs made in Australia or NZ, and those factories were only turning out low quality plugs for the locally assembled/manufactured cars, there were just no resistor plugs available. Then someone discovered that Ford owned Autolite, and any Autolite spark plug could be ordered from a Ford dealer by part number, including plugs for non-Ford cars, the order word go through the system, and eventually a box of American made resistor plugs would arrive.
My dad ran an auto-electical business at the time and had stocks of dozens of models of resistor plugs, which with solid leads would make many engines run better than solid plugs with resistor leads. This trade was cut short when the customs department discovered that Ford were illegally importing american plugs without an import licence.