Xantia - stalled

[Jaf]

Hi guys. Hot today, 35 degrees. Had air con on and engine was running at around 100. Engine cut out twice, re-started easily. Both times was when coming to a stop, with car pointing downhill. I'm thinking a sensor being naughty, but this is the most modern car I've had so don't know what to look for. I do remember last year when the car got pretty hot I couldn't re-start the engine after stopping for 5 mins, had to bump start her.

Any ideas? Thanks.

[addo]

TDC sensor.

[Old-Guy]

100° is awfully hot for an XUD9 - should be 81° (85° for Activa). In my experience, wax thermostats fail progressively as the wax leaks out of the capsule so that although the thermostat does still open, the movement gets progressively less until you have overheating problems. Unless the thermostat has been changed in the last few years, I'd change it (neither difficult nor a long job) before you cook the head. At the same time, I'd give the radiators a good hosing from inside to out to remove the worst of the dead bugs leaves and other cr4p.

[Jaf]

Thanks both.

Engine gets up to 105 on one hill! Cools down in seconds once I hit the top of the hill. Lorries and even some cars often have to stop mid-way up, there's a lay-by for that purpose. To give an idea of the torture, when coming back downhill I freewheel for 10kms. Both rad and thermostat are good, antifreeze due for a change this autumn.

This is the first full summer with working air con, engine cooled down to 90 very quickly when I turned it off. I guess it produces a lot of heat. Certainly uses a lot of fuel.

Will investigate tdc sensor.

Might be a good idea to run a winter thermostat (car runs at at around 75) and a summer thermostat. Will have a look and see what I can find.

Going to be 40 tomorrow. Eek!

Just been to get the post. 8kms away on the "good" road. Only me in car, yesterday 3 of us and shopping yesterday. Engine barely hit 90, down to 75 when freewheeling. Didn't cut out. Yay!

Does the tdc sensor only measure top dead centre? Or does it measure revs?

Thanks!

[addo]

Your AC shouldn't use a lot of fuel.

[Jaf]

Yeah, I've read 7 percent but it's more like 20. Goes from 950kms a tank to 800! It has to work very hard as most journeys are short, 20mins or less and there's no shade! My guess is the system isn't in tip top shape, had second hand compressor last year due to huge leak.

[Old-Guy]

Still sound like a tired old thermostat to me. After a 'hot & bothered' experience on the M4 when we first had our 96 1.9Sx estate (the Green Lady) after which I changed the very tired wax thermostat, the temperature gauge never goes above 85, that fully laden plus a 1/2T trailer on back and going up Haldon Hill (at the Devon end of the M5) in heavy traffic. With the whole cooling system in good shape, the radiator fans should be able to cope with everything you throw at it - even in Spain.
Is the auxiliary drive (alternator, hydraulic and water pumps, a/c compressor) belt in good condition and correctly tensioned? It's got to transfer a lot of power from the crankshaft pulley, under heavy load condition that's where it's most likely to slip and that will affect the water pump too. Unfortunately, it's a common (but stupid) trick-of -the-trade to squirt WD40 or similar on a squealing belt to shut it up instead of tensioning/replacing it. It'll slip even more than before, but silently!

[Dommo]

Guy, the water pump is powered by the cam belt rather than the auxiliary belt.

[Jaf]

Well when the weather, and me, has cooled down down a bit I'll have a look at the thermostat. It's not very old, a couple of years, but that's not a guarantee that it's not faulty. Pretty sure I've a lower temp one in the garage. Cam and fan belt a couple of years old too, fan belt nice and tight.

It's still 36degrees, at gone 8pm!

[Jaf]

Do you know I had totally forgotten about this. She stalled a couple more times in the summer, always with the air con on and her nose pointing downhill.

Yesterday I had 5 of us in the car and had to put the air con on. In winter! It was only about 26 and the engine didn't get past 80, she behaved and didn't stall though I did notice the power decreased.

So my question is: is there a overheating cut off? Or would that still indicate a possible problem with the tdc sensor? I did replace anti freeze and thermostat (though it opened correctly in a pan). Guess I'll see if she's still faulty in the summer.

[citroenxm]

Are the cooling fans DEAFENATLEY working?? They are common for now working as the relays between the fans behind the small triangular cover tend to corode.

As soon as you switch the Air Con on, both fans should run at slow speed all the time!

Theres no such device for cutting out when too hot, hence why soo many XUds had warped heads in the past.

[Jaf]

Yes the fans run at low as soon as air con switched on and at high speed when the rad's up to temp. Can't miss second stage fans, sounds like a train. Apart from the demon hill I never let her stay hot for very long. I've done a few head gaskets years ago at work, heads we sent away for skimming, don't fancy the job on this engine. I'd say that cos she cools so rapidly when freewheeling that the rad's in good nick? I did flush the engine and rad when I changed the anti freeze. Despite it only being 2 years old there was a bit of rusty water in the engine.

The air con really does suck up a lot of power though, with it on I have to use a lower gear a lot. I wonder if the stalls were as simple as the engine is just low on power and it's me stalling...but I haven't stalled a car in years! I have occasionally pulled away in third though so perhaps I'm losing my mind.

I shall no doubt forget all about this until next time she stalls. Still haven't completely solved lhm leak so one thing at a time.

[Estately]

Hi Jaf,
We have driven our Xantia 2.0l HDi 90 to Spain from the UK to the coast between Valencia and Alicante on each of several years and in August.
The uphill gradients in the Pyrenees certainly took ours up to an indicated 115C and I felt that the need to ease off the throttle would be a good idea. At motorway speeds dependent upon gradient, the temperature would be between 90 and 100C.

The above temperatures only occurred after a cam belt/water pump change, prior to that I do not remember the temperature rising or settling as high.
Both before and after new cam belt the water temperature in the UK rises a little at motorway speeds no matter what the vehicle loading or outside temperature is.

After seeing the higher temperatures and suffering the agony of having to slow down; before the next Spanish trip the car was given a good flush and also a thorough clean of the space between the air con and engine radiators.
There was a lot of debris in there and a spray through the radiators cleared a fair amount of road dust.

Having done all that and replacing the thermostat, the temperatures still rose on subsequent visits, it handled an outside temperature of 42C driven round Zaragoza, the climate control did exactly that and if not for the indicated outside temperature you simply would not have known.
There has been no tendency to stall.

Un-tested theories would be:
That the replacement water pump was not up to providing sufficient circulation for these conditions not found in the UK.
That the water temperature sensor has degraded in some way and is giving an inaccurate reading.

Our Xantia is in semi retirement now and unlikely to go to Spain again but a simple test for you would be to remove the thermostat for a while when the weather heats up, check the engine temperature and see if it still wants to stall.
May be worthwhile checking for water in the fuel filter bowl and ensuring that the filter has been changed within the necessary distance.
I think that some thermostats, because of poor design, can restrict water flow even when fully open, but is only noticed in the more extreme conditions.

Hope that helps

Andy.