Xantia Overheating

mallyg · Post by **mallyg** » 09 May 2006, 19:33

My M Reg Xantia 1.8i overheats on relatively short journeys. I Have checked the radiator fan and it comes on ok. At what temp should the fan come on because it doesn't come on until the car reaches approximately 110 degrees. I am not sure but I suspect an air lock somewhere in the system but am not sure how to bleed the system and where the bleed valves are. Any suggestions as what could be wrong would be gratefully received. Thanks in advance,

Homer · Post by **Homer** » 09 May 2006, 20:04

110 is a bit high, you should be getting the fan cutting in between 90 and 100.

mallyg · Post by **mallyg** » 09 May 2006, 20:07

If it should kick in where you say where does the problem lie. is it a switch fault or something else? Thanks

AndersDK · Post by **AndersDK** » 09 May 2006, 21:02

Could very well be an airlock.

Bleed the system using the homemade header tank approach :
(Engine cold and not running !)
Find a plastic bottle with a neck diameter that fits snugly down the coolant filler neck. Cut off the buttom of the bottle and fit bottle down the coolant filler neck. Now top up the bottle until half filled (approx ½ a liter up).
The whole idea is to get a fluid level which is positively higher than any point in the cooling system - including the heater matrix in the dash.

On the radiator there should be a bleed screw either end at top. Some looks like a large ordinary screw, others look like a finger twist fin. Unscrew until coolant seeps out - even remove completely - to be positive that fluid only (no air bubbles) flows out. Top up your header tank if necessary.

Re-fit and close the radiator bleed screw.

Now start engine and let idle. Blip the acc now and then to make the water pump circulate the coolant and any air. At some point there may be large burping and the fluid level will sink. Keep your header tank topped up to a level just barely over the filler neck

Stop engine before it reaches hot temperature. Then remove your header tank (accept un-avoidable spillage) and refit filler cap.
Now run engine up to normal operating temperaure - observe excess coolant is expelled while engine heats up. This is absolutely normal.
WARNING : Do NOT remove the filler cap or touch any engine parts. Its scalding hot now

During the next couple of days the coolant system should "settle" the fluid level while expelling air locks to the filler cap vent valve.

oscarloco · Post by **oscarloco** » 09 May 2006, 21:46

You should also check your thermostat as that little fella tends to get stuck.

mallyg · Post by **mallyg** » 11 May 2006, 18:14

Thanks for the information. Had a look earlier today and found no bleed valve on the radiator but i have found one on the thermostat housing and one that comes off the side of the thermostat housing and is about half way along a pipe that leads to the bulk head. I will have a go this weekend

8304 · Post by **8304** » 12 May 2006, 08:40

ask clogzz about the bitron unit, i dont know anything about them or even if your car has one but they have been known to cause all sorts of cooling fan problems on xantias.....

Post by **RichardW** » 12 May 2006, 09:40

OK, time to dig my oar in this thread.....

1. I think spontaneously occurring cooling system air locks are a myth - how can you suddenly get an air lock - unless work has been done on the system - or it's losing water?

2. If the fans don't come on till 110 there is something wrong with the fans and / or control system

3. If the car overheats on a short journey in normal driving there is a problem with the cooling system (blocked rad, failed thermostat / water pump, knackered head gasket). But not the 'air lock'!!

How to proceed? First need to know overheating pattern. Does it OH in normal driving, or only when stood still? When the temp has come up to say 90°, what is the state of the top hose (hot / cold), and the rad (hot all over, hot at the top & cold at the bottom?). Next, any signs of HG failure? Water in oil or vice-versa, pressure remaining in the system when engine is cold, engine building pressure in cooling system in <1 minute from cold start, bubbles in header tank. Next, fans. Assuming no aircon, and 2 rad fans - they should come on slow speed at about 90°C, and onto high at somewhere above 100°C. I presume they work on the same principal as the TD fans, so you should be able to test the performance by shorting the rad switch (see thread from last week by DaveW about fan diagnosis). Armed with this level of info, should be able to make a reasonable stab at diagnosis.

Clogzz · Post by **Clogzz** » 12 May 2006, 11:45

And taking my turn.

8304 wrote:ask clogzz about the bitron unit

Had seen this topic earlier in the week, but didn’t participate because it looks like we are talking about a single fan, and therefore I think without air conditioning or Bitron.
BOL shows a single fan arrangement, switched directly by a 2-pin radiator sensor switch.
Same BOL page shows a single fan switched by a 3-pin sensor and one relay, for two fan speeds.
That may be what you have, with the low speed not working.
Next BOL page shows the 2-fan system, with 3 relays and 3-pin sensor, but without air conditioning.
Air conditioned 2-fan control with Bitron is shown here:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=17012

The DaveW thread that RichardW is referring to, is this:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=18965

We would need to know if the car has air conditioning, how many fans there are, and how many pins the radiator switch has.
If it’s got air conditioning, it doesn’t have a radiator sensor switch, but a Bitron controller instead.

mallyg · Post by **mallyg** » 14 May 2006, 20:30

Hi all

Right, there car overheats only when it is stood still i.e in traffic, has no air con and only has one fan. I didn't know the fan has two speeds. The fan only comes on around the 105/110 degree mark. Thermostat i think is ok as the temp needle goes down to around 80 degrees at around the 90 degree mark and then up again. where do i find the rad switch. Not being mechanically ( as regards cars anyway) I haven't much of a clue of where to find things. Any help is much appreciated. Thanks

Mandrake · Post by **Mandrake** » 14 May 2006, 20:47

mallyg wrote:Hi all

Right, there car overheats only when it is stood still i.e in traffic, has no air con and only has one fan. I didn't know the fan has two speeds. The fan only comes on around the 105/110 degree mark. Thermostat i think is ok as the temp needle goes down to around 80 degrees at around the 90 degree mark and then up again. where do i find the rad switch. Not being mechanically ( as regards cars anyway) I haven't much of a clue of where to find things. Any help is much appreciated. Thanks

When stationary at traffic lights for a long time or moving slowly in stop start traffic it is normal for the engine to get hot relatively quickly, (due to lack of airflow over the radiator) and get up to 90 degrees, at which point the fan(s) should come on at normal speed and keep it between 80 and 90.

If the fans are not comming on until 110 then naturally the engine will reach 110, and overheat. So there may be nothing wrong with the rest of the cooling system, it could just be a fan control problem.

When they finally do come on do they seem to run really fast ? Perhaps the normal speed is not working but the maximum speed is...(which is REALLY noisy)

Also, does the car overheat on a steady journey at open road speeds ? If not, and it hovers around 80 degrees on such a trip, that also suggests it could just be the fan system at fault..

Regards,
Simon

Clogzz · Post by **Clogzz** » 15 May 2006, 12:57

The radiator switch is at the top of the radiator, probably at the battery end.
It has a plug with 2 or 3 wires.
Two wires for single-speed control.
Three wires for two-speed control.

mallyg · Post by **mallyg** » 15 May 2006, 19:43

Found the radiator switch, its halfway down the rad at the battery end, two wires going to it so i guess it must be a single speed fan. Took the car for a 20 or so mile drive today and everything seems ok. I did undo the bleed valve on top of the thermostat housing and the one halfway along the pipe so i think this has done the trick. If anything changes i will let you know. thanks all.

mallyg · Post by **mallyg** » 21 May 2006, 21:26

Back again

Car overheated when stood in traffic and fan did not come on until around the 105 degree mark. If its a fan control problem where should I be looking and what should I be looking for. Any help very much appreciated thanks

fastandfurryous · Post by **fastandfurryous** » 21 May 2006, 22:57

You need a new radiator thermal switch. Everything else seems to be working correctly.

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