406 overheating/over pressurising.

caveman_si · Post by **caveman_si** » 14 Jan 2008, 18:55

Car is a pug 406 lx 99 T-reg with ac.
Engine had classic Head gaskit symptoms, pressurising coolant pipes, mayo in the oil, loosing a little water, water/oil mist in the oil fill up.

So I had the HG changed and the head was replaced as it couldnt be skimmed.

Now the engine is back up and running and the top coolant pipe is still getting pressurised.
BUT the cooling fan doesnt seem to be kicking in. Had it running for ages and it didnt kick in.
When the AC is turned on the cooling fans kick in, when the right electrical connection (as you look at the engine bay from the front) on the fuel filter the fans kick in.
Once the fans kick using the above methods in the temp drops.

So my question is my pressurings and over heating a result of the electrics or a futher issue with the Head and Head gaskit or something else?
If it is electrical any ideas as ive not got a clue?

Cheers

Clogzz · Post by **Clogzz** » 15 Jan 2008, 13:22

Is the temperature indication normal at road speeds, when the fans shouldn’t spin ?
Looks like the fan switching works, but hot water must get to the temperature sensor to switch them on when the engine gets hot.
That leaves the thermostat; or air in the cooling system; low coolant; obstructed radiator, either internally or externally.
Gasket leaks by themselves cause no overheating, but they cause loss of coolant by pressurisation or intake into the engine, then out the exhaust.
The gasket and head changer has obviously ‘overlooked’

something.

caveman_si · Post by **caveman_si** » 15 Jan 2008, 14:35

Themostat was new just before the penny dropped that the head gaskit or head was on the way out.
Radiator is new ish (not original its a nissans rad and looks in very good condition) the whole coolant system has been flushed (both ways) prior the head being diagnoised.
(There is the possiblitly that there is an airlock from it being refilled and I am going to top up the coolant system again using a header and bleed to make sure but I doubt it)

If the car is left in idle then the engine gets up to temp 90° and sits there with the coolant pipes pressurising due to the heat. The fans dont kick in at low speed. Took the car for a run locally 30-40 mph and the temp hit 100° again no fans kicking in.
If you turn on the AC the fans kick in on the fast setting (I assume fast setting ive not seen them go slow), turn it off and they stop. If you unplug the temp sensor (I am assuming temp sensor) on the base of the fuel filter housing/top of the themostat then the fans kick in on the fast setting (again assumed fast setting)

So having had a bit of search it looks possible the low speed setting isnt working ie the settign the cause the fans to come on at low when the temp hits 90° ish ?

SO if I am right I think there is 3 relays between the fans that could be at fault possibly one or more fuses out, or the bitron unit (where ever it may be) could be up up the duff. Also the possibility that the temp sensor has gone?

Any idea of which order to start ruleing things out? Or anybody think it something else?

cheers

caveman_si · Post by **caveman_si** » 15 Jan 2008, 16:54

Manage to have a quick look, after work today, at the car and the passenger side fan does not kick in when the AC is switched on or when the temp sensor is unplugged. So possibly a few things wrong, broken fan and a dodgy relay/wire/fuse.

Post by **CitroJim** » 15 Jan 2008, 21:16

Certainly the lack of working fans is not helping but that is not the whole story.

On all the XUD engined cars I have ever owned, the fans cutting in to keep the engine cool in winter has been a very, very rare occurrance, only in very exceptional circumstances such as a queue after a long hard run or whilst caravan towing. Certainly the temperature should not rise to 100 degrees on a 30-40mph local run. On idle, it should take about 20 years to get to 90 degrees in this weather.

After 30mph the fans will have no cooling effect whatsoever as the forward motion of the car above 30mph pushes far more air than any fan can.

I know you have but check and double-check it's bled properly. 405s are notoriously difficult to bleed due to the expansion tank being low-down on the side of the rad and I guess 406s are similar. You need to use a high header tank. My last 405 had broken bleed valves and I had to resort to popping off a small bypass hose to get it to bleed. Back in my early 405 days I nearly killed mine because it was such a

to bleed.

Speaking of bypass hoses, did they all get replaced properly and are they clear? The one that connects to the little plate on the head just in front of the injection pump is small-bore and prone to getting blocked but despite its seemingly lowly status, it is critical. The spigot on the head plate is terrible for getting furred up.

Nissins rads are fine in my experience.

Have you checked to ensure the air path to the rad is clear? If it has an aircon condenser and/or an intercooler in front of the rad, is this fully clear?

Is the rad feeling warm all over or does it have cold areas?

About the only other thing that could cause it is severely retarded injection timing but if that were the case, the symptoms would be easy to spot.

I'm concerned that this problem has come about since the head was replaced. Was the head given a light skim before fitting and was the head pressure tested and checked to ensure all its waterways were completly clear before fitting?

Do you have any signs of pressurisation of the coolant and do you see any bubbles?

Clogzz · Post by **Clogzz** » 17 Jan 2008, 16:41

passenger side fan does not kick in when the AC is switched on or when the temp sensor is unplugged

Both fans always have to do the same … both slow or both fast.

Some inspiration here:
http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

caveman_si · Post by **caveman_si** » 17 Jan 2008, 20:33

Cheers Clogzz, after much reading ive repeatedly come across that link and diagrams, which are the same as in the Hains BOL but that website explains it so much better.

So now im thinking the left fan (passengerside) or the left fan relay has gone. So they are going to be my first port of call, then possibly the temp switch or the bitron unit.

Does anyone have a picture of a bitron unit? and know exactly where i'll find one on a 406? Save me a few hours this weekend in the pouring rain wondering if this or that is it.

Cheers

Clogzz · Post by **Clogzz** » 18 Jan 2008, 13:20

No certainty about where to find the Bitron on the 406, but the usual place on the Xantia is under the passenger’s side headlight.

The Bitron isn’t causing the fault, because ‘one fan’ faults are caused by relay sockets, fuses and the like.
The temperature sensor isn’t faulty either, because its disconnection causes the fans to spin at high speed.

A sort of guide to fan spinning speeds would be to call the slow speed ‘steady’, and not audible from the inside, while the high speed really is ‘loud’ enough to worry the pedestrians.

More Bitron and fan relay pictures in this bucket:
http://s132.photobucket.com/albums/q23/Clogzz/

caveman_si · Post by **caveman_si** » 22 Jan 2008, 12:10

Quick update.
After braving the rain and doing some work on the car over the weekend some success. The change over relay connections had disintergrated as had some of the wiring loom going into the rear of the connector.

Sourced some new relays and the connector it goes into. Took the old one off and wired in a "new" one and put everything back together.

Only done a quick test by disconnecting the temp sensor but both fans now work at the "high" speed setting. And what a speed it is was expecting my clothes to get sucked off me sounded like a jet engine winding up.

Hoping to get the engine up to temp in the next few days weather dependant and double check that its bled properly and that the fans kick in at the low steady speed. Fingers crossed eh.

caveman_si · Post by **caveman_si** » 23 Jan 2008, 16:28

ANother update had the car running for an hr today.

The fans kick in on a steady speed when the ac is turned on, they go to high speed when the temp sensor is unplugged. But they dont kick in when the rad/engine gets hot.

The rad is hot all over and the engine is running fine had it running for a 30 mins, and checked it was bled and again that was fine.

Any ideas as im lossing the will with this one?

cheers