2.1td Cooling System Gremlins, Low coolant warning and erratic fans

[kenhall1202]

Hello readers,

While driving home yesterday from a successful MOT test (tester was impressed by the HID conversion by the way!! but didn't comment otherwise) the smile soon left my face when I saw the low coolant and STOP lights flickering faintly (temperature gauge stayed normal). After leaving it half an hour to cool off, the header tank level was found to be normal.
Removed the header tank level probe, cleaned a small amount of crud off it and replaced it but faint low level + STOP lights still showing, but later they went out!. I then noticed that the two radiator cooling fans were running at low speed, with the ignition switched off, something I had never seen happen before even after a hot summer run. Disconnecting the plugs from each of the three visible temperature sensors (two in front of the black plastic fuel filter/heater housing and one in the gearbox end of the cylinder head) made no difference - the fans kept on running!! even though the engine was quite cool by now.
I stopped the fans by pulling out the three relays which sit above the nearside headlamp (after unsuccessfully trying a substitute new relay in each position) and gave up at that point as the light and weather were against me.

I've since scoured all my XM info, without success, to find a cooling fan circuit diagram specifically for a '96 2.1TD (non aircon).

Can anyone please help with the following:

1. A relevant circuit diagram or failing that a description of which bits do what.
2. Is there any electonic control unit associated with cooling fan operation? or is it just simple thermal switches + relays for non aircon cars.
3. Are there any other temperature sensors/switches other than the three mentioned above and which one controls what? ( ie temperature gauge, fans or input to EPIC )
2. Is the thermostat on this engine (XUD11ATE?) located in the water outlet of the plastic filter/heater housing?

Regards

Ken

[xmexclusive]

Hi Ken

Somewhere in the back of my mind there seems to be an association between your faint dash lights and a failing altenator. The checks are easy so thought it worth mentioning.

Regards

XMexc

This post has been edited by xmexclusive on December 08, 2007 06:41 pm

[Peter.N.]

Hi Ken

There is a bitron unit somewhere that controls the fans, does the series/ parellel bit according to the temperature. Mine plays up now and again, tells me the engine is overheating and puts the fans on when I have just started and the engine is cold! It can come on at any time. I havn't been able to find the cause as it won't do it long enough. Its been doing it for the last 60k so I have stopped worrying about it.

Your remark about the water disturbed me a little. It should be clean and blue with about 50% antifreeze, otherwise you are likely to be fitting a head gasket in the not to distant future - guess how I know!

Peter.N.

[onthecut]

Hi Ken.

My last 2.1 had an intermittent, spurious over temperature warning and erratic fan behaviour. Given the gauge was OK and it didn't in reality overheat or lose water, must admit I just lived with it. Sometimes there was the sound of a relay chattering somewhere behind the instrument / warning lamp panel, which seemed related. I know this isn't much help in diagnosing the issue, but at least if you're not actually losing water or overheating, you needn't lose sleep over it. Have to say, though, I'd at least leave one fan working meanwhile.

Mike.

[kenhall1202]

Problem solved! (fingers crossed)

One of the two wires coming out of the brown temperature sensor plug had broken just where it exits the rubber cover and was only held together by the insulation. It finally came apart when I disconnected the plug to check the sensor resistance.
Application of a quick soldering job and some heat shrink insulation appears to have fixed the problem.
The random operation of the cooling fans at full speed, caused by the broken wire making intermittent contact, might also explain why the engine has been running a bit cooler than normal these last few months, although I still intend to fit a new thermostat.
For anyone interested in the principle of operation of the 2 speed cooling fans there is a good Aussie website article here for the Peugeot 306 (probably applicable in principle to all PSA cars of similar vintage). http://www.peugeotlogic.com/workshop/wshtm...fan2/fanop1.htm

Regards

Ken

[magic carpet]

My xm had the flickering light symptoms like yours, i found a new sensor fixed it. The flickering has started again though after a year of no flickering, think i'll check the plug. There must be 2 xm's in west cumbria with hid lights now ken!

[Cattledog]

Thanks for the help' I'll check out the temperature sensor wires and see if that fixes my problem.

Regards,

Cattle Dog