Odd overheating problems

[allstaruk]

Hi

After a few of my previous threads I have come to the conclusing i have a problem with overheating that is getting progressively worse,

On normal light driving at 80mph in 5th I see water temps of 100deg c. I went to the petol station yesterday drove there with the water temp at 100 filled up lest the petrol station stopped at a set of lights where I waited for 2 mins and the temp rose to 125 i i started moving again and it didn\'t seem to drop so I pulled over and stopped the car and left it to cool right down.

This morning at 5.30 I went to go to work I started the car defrosted it and started driving with 2 miles the water temp was ar 115, so I stopped and let the car cool, upon settting off again it stayed at 100 for the journey to work, it was apprx 2 deg c outside this morning surely it shouldn\'t heat up like that while driving in this cold.

I have just taken it for a drive to see it I can work out what its doing, with the air con on the car temp rises very quickly and to dagerously high levels with the heater on in the car an no aircon the car temp rises to 100 and without the air con or heater the temp sits about 95.

To me this sounds like a thermostat that is malfunctioning, I am not quite sure how the cooling is set out on these cars so any help would be great as its due its MOT on fri and if its overheating this badely I can\'t risk driving all the way to reading.

All these temps are measured from an afermarket blitz gauge plumbed into the coolant filller neck.
Al

[allstaruk]

I have just driven it home from work and pulled onto the drive this is such a short drive it barely has time to warm up so when I pulled onto the drive I put the heater on and the water temp instantly rose 15 deg and then I put the aircon on and it started ti rise again, when I turned the aircon and heater of the temp started to drop.

I\'m now very confused.

[rx7veilside]

these are dangerously high water temps with my big fmic on cruise 88-89 rising to 94 if stopped but fans kick in at 95

[allstaruk]

I\'m aware of this thats why i need to fix it but I\'m not sure what to check, could it be the thermostat?

[Martiny]

Yes its odd the Temp goes up with the aircon switched. This, I think should bring the temp down because it forces the fan/s to come on.

On some cars, I think that having the parking lights on also forces the fan on, but I dont think this applies to my car, but you might try it.

Not sure what constitutes too hot, though, what did the standard gauge do ?

[Laeeq]

Do you know at what temps the fans come on and do they stay on afterwards all the time.  With the fans on the temps should drop down.  Or may be the fans are not comming on at all...

[iaint]

After a brief period of being stopped with then engine off it\'s not uncommon to see heat-soaked temps above 115C.  You should never see this with the engine running, late 90s maybe in traffic, poss as high as 102-5 in very warm weather in traffic.

No clue why you\'d see the temps go up with heater/aircon on, never noticed it make much difference to mine either way except for having the heater on full blast blowing out hot air on track - temps kept sensible!

Reasonse for temp problems that I can think of:
- dodgy thermostat
- air-lock preventing water flowing round the system (check to make sure the rad is getting hot!)
- water seal failure - exhaust gas gets into the coolant when running - this adds too much heat to the coolant for it to disperse.
- silted up rad.  Pre rebuild my rad was flowing at 40% capacity.

might be something else though!

[Laeeq]

I think the fans are not kicking in at set tepms they should.  have a look again with the car running and see if they are on or off....

[iaint]

Hi

After a few of my previous threads I have come to the conclusing i have a problem with overheating that is getting progressively worse,

This would make me suspect the water seals.  Are you having issues with low coolant leves and need to top it up regualrly?  IF not then it\'s probably something else.

[allstaruk]

My coolant levels are the same now as they were months ago and havent needed topping up, I check them quite regularly and its stayed just bellow the top of the filler neck for ages now.

When parked on the drive the fans come on at 95 deg on the gauge.

Gonna take the thermostat out this afternoon and see if it opens when I put it in a sauce pan of water, could the waterpump have stopped working?

[nikp]

It could be a lot of things! :p

I would say the first thing to check, the very first thing, would be the gauge itself! Make sure it\'s plumbed in correctly, and wired up correctly (if it needs to be wired up). Then, if that\'s ok, start looking at the other basic components of the coolant system. Give the whole thing a good flush, refill, purge air blocks out of the system and try again. Replace thermostat as a matter of course if you haven\'t done that for a while. Then if all of those fail to sort it out, check the water pump and also get the coolant system pressure tested. Unlikely to be the water seals, i would have thought, if you\'re not losing any coolant.

However, i am somewhat curious about the tmep gauge readings, as at 125 degrees, that\'s boiling coolant in my book running at 1.9 bar (as the coolant system does). Boiling coolant is bad, and usually fries rotor housings, and therefore you\'d expect to lose coolant. So....odd!

[allstaruk]

I have two identical gauges one for oil temp and one for coolant both are mechanical so I will swap the sensors over and see if I still get the same readings,whats the best way to drain the coolant and can anyone recomend a coolant flush.

[nikp]

I also believe you have your temp gauge plumbed into the base of the thermostat housing (where the fillier neck is) - with a nice flow of coolant, that should actually be slightly cooler, as it\'s coming from the radiator - so it\'s coolant that\'s just been cooled.

Perhaps it\'s worth unplumbing it and putting the sensor in a kettle of boiling water to verify that it reads 100 degrees C - then you can be confident that the gauge is accurate. Perhaps (!) since you say both gauges are the same make, that they are both reading poor signals, and you have no problems at all. Verify that the gauge is accurate.

[allstaruk]

I can\'t be bothered to unplug it totally I\'ll take the kettle to it, I\'m fairly convinced that I do have some for of problem thought.

What would I expect to happen if the thermostat had gone?

Also how would i check the water pump.

[nikp]

Bring kettle to it just as good!

If the thermostat is stuck closed, then the coolant would never get to the radiator, therefore increasing temperature around the engine until the weakest link gives way and the coolant system blows! However - you have your sensor plumbed into the system after the thermostat, so this is unlikely to be the problem. If that were the case, you would see your temp gauge not showing any temperature, or lower than normal temps because less coolant is being driven through the rad.

Your temps get very very high within a couple of minutes driving: that\'s very quick to get that hot, even for an FD. I\'m gonna pin my money on in-accurate gauges!