Coolent temperature sensor

[PAUL SARGISSON]

The temperature gauge on my 2.5 Conney has started to wander instead of staying mid point, most of the time it is reading low then moves up to normal but then slowly moves down. The car runs fine and coolent level is correct, also when I turn the ignition on the fuel gauge goes full scale then drops to correct level but the temp gauge does not move. I may be wrong but I am sure they both used to go full scale. Any one had this problem or an idea what is wrong, I am considering replacing the sensor but it looks like the inlet manifold will have to be removed to get to it. Thanks Paul S

[KWIL]

Temp guage does not swing, but the integral leds do illunminate and go out.

Use the IPK diagnostics to check actual coolant temperature, if this shows the same swings then suspect sensor but I doubt it will.

[SD1too]

Originally Posted by KWIL

Use the IPK diagnostics to check actual coolant temperature ...

I agree with Ken that this is a useful test although in theory a faulty sensor would cause the temperature gauge to remain in the 'cold' position, the high temperature warning light to illuminate and the radiator fan to run continuously at high speed.

If the digital coolant temperature displays the same readings as the gauge, the problem might be that your thermostat is faulty.

Simon

[PAUL SARGISSON]

I took the car out for a run and monitored the temp gauge readings, when driving in town below 30mph and stop start driving in traffic gauge reads steady mid scale above 40 mph constant speed driving gauge between quater and mid scale. driving at a steady 70 mph in clear air gauge reads quater scale, I am starting to suspect my thermostat is stuck open also the car appears to take longer to warm up.

[SD1too]

I agree with your diagnosis Paul. Will you be doing the replacement yourself?

Simon

[PAUL SARGISSON]

Originally Posted by SD1too

I agree with your diagnosis Paul. Will you be doing the replacement yourself?

Simon

Yes I have just read the key hole method so will give it a go some time. I have a thermostat kit from DMGR that I purchased about four years ago and put aside for when required.

[stocktake]

Exactly the same symptoms as mine, I changed the TStat 4 days ago and then had a 230 mile round trip to the Nano meet and back. No more problems. I also use the keyhole method, ( well i would wouldn't i as i was one of the first to be brave and try it this way). Have to say that was quite a few years ago now and although the stat never leaked it did get sluggish hence the change.

A little advice is to purchase the full kit and original spec equipment.

Another bit of advice is not to cross thread the bolt that holds the stat and elbow in place, if you do then prepare to swear a lot, have to grind down one of your taps from your best set to be able to get in there straight and re-tap the thread.

Oh and have a copious supply of everplast to hand...

[SD1too]

Originally Posted by PAUL SARGISSON

Yes I have just read the key hole method so will give it a go some time. I have a thermostat kit from DMGR ...

Paul; based on my experience my advice is as follows:

• If you can find one, buy the improved thermostat housing with the three supporting legs. Otherwise, as Stocktake says, don't use unbranded parts of unknown origin. The thermostat housing assembly is PEM101050.
• Retain as many of the original parts as you can. Unfortunately adopting the keyhole method increases the risk of breakage which prevents this.
• Observe the torque setting (18 Nm) for the screw securing the curved pipe and thermostat housing. This will be difficult if not impossible using the keyhole method.
• After reassembly, slide the two plastic clips on the straight pipe outwards so that they bear against the water pump and thermostat housings, then tighten them. This operation crucially prevents movement of the whole assembly in service which, I believe, is responsible for the flattening of the 'O' rings and leakage of coolant.
• Should you decide to use the full workshop procedure, which takes longer but affords much improved access and visibility, renew the 'O' rings (CDU 3858) on the original curved and straight pipes.
• Ensure that you refill and bleed the system by raising the expansion tank and not opening the bleed screw when the engine is running (see MG Rover procedure reproduced on this forum).

Another advantage of using the full workshop procedure is that, with the manifold chamber off the car, you can remove the cam cover on the R.H. bank and clear the breather orifice if not done recently. You can also take the opportunity to check or renew the R.H. bank sparking plugs.

Simon

[PAUL SARGISSON]

The stat housing I was sold from DMGR is stamped PEN100510 and came has a three part kit with the straight and curved pipes which have new "O" rings. Do I need to dump this and buy a new one ?.

[SD1too]

Originally Posted by PAUL SARGISSON

The stat housing I was sold from DMGR is stamped PEN100510 ... Do I need to dump this and buy a new one ?.

The numbers forming part of the plastic moulding are different from the part number under which the item is sold. Was it supplied in manufacturer's packaging and labelled PEM 101050? The two genuine MGR thermostat assemblies I've seen also have 82 degrees moulded into them (incorrectly because it opens at 88 degrees). So if your DMGRS supplied hasn't got that it may well not be a genuine MGR part but it might be ok. Who knows? The decision is yours.

Simon