(T) Underheating!

I have had a problem with overheating, rad had been a little suspect for the past 6 months, eventually got around to changing it last week. After changing the rad my temperature when running stays around 70 degrees. There is an issue that I have had before and after the radiator change, when travelling at a constant 60-70 the heater goes cold. I have found a couple of ways to correct this. One is to stop and start the car again, the heater then will warm up once more. Or to stay stationary for a while and drive off again when the temp has increased to maybe 80 degrees. I think all of the air is out of the system, I have taken the expansion cap off a few times when hot and cold, have topped up the coolant a couple of times as a result. All of the hoses top and bottom on the rad and the heater feel warm / hot but the resulting air from the blower in the car is cold. There is a similar sympton when leaving the car idling after just starting on the drive, the heater will warm up and the temperature will climb to a maximum of 80 degrees, cannot get it anywhere near 90, the heater will go cold, then if you rev the engine, blipping the throttle a few times the temperature guage will plummet back to 60-70 degrees and the heater will warm up. Any ideas on where to check?

Have you used the two bleed screws to get all the air out of the system? There's one behind the driver's headlight and another at the back of the engine bay on top of one of the hoses which feed the heater.

Thanks for that...was wondering where the bleed screws are for these....
I will undo them tomorrow and see what happens.

Sorry if i havent read your question right, but are you not getting any hot air through the fan?

EDIT- i re-read it , and it sounds like you may have an airlock in your system.


My friend had something similar and he said that the car was under reading as there was an airlock where the sensor was. If that makes sense....

So like pete said, bleed it and re-fill to remove the air lock

If that doesn't work, it could be a sticky thermostat.

The temperature on the driveway problem is fairly common on 899 cars. The water pump will not circulate enough water at idle. The water in the engine becomes hot because it is not being pumped through the radiator, when you increase the revs, the pump increases the flow and the cool water enters the block.

Cheers

D

Hi,
As "Fixitagaintomorrow" says, could be a stuck open thermostat, just had that problem on my 900s, new thermostat and all's well.
Fiat thermostats aren't that cheap mind, about £26 is quite a bit for one of these devices and that was a patern part not a Fiat part.

Paul T

Merry Christmas and a Happy New Year

Aaaaaagh! £26?!?! My Punto's running cool at the mo, got to be the 'stat as I've flushed, refilled and bled the cooling system recently. It doesn't go much past 1/4 of the way up the temp gauge even after razzing it up the motorway for an hour; only way it heats up properly is when it's stood tickin over for ages (eg in kfc drive thru Q ). Bloody car! More expense!

Each thermostat is a different price.. it depends how complicated the design is. Cheapest one I ever bought was for an Uno @ about a tenner.

Ralf S.

Just done my thermosplat, the part cost me a mere 11 squid from Motosave. The old one was fooked, it was stuck open (tested by blowing through it!), now the motor runs at halfway up the temp gauge like it should and the heater's actually hot