Technical Overheating problem!!

[Daleyboy10]

i need help quickly.
last week my car (uno 1.1L 60s 1108cc fire) gave up the go 50 miles from my house and had to be towed back to mine.
i knew it was the gasket.
but as i have done all the gaskets i have another problem.

it doesnt boil the water or lose water but it does it really hot and the temperature keeps rising and the fan does not come on at all.
i shorted the fan to see if it is working and it came on so something is not right along the line.
the hose at the top of the resevoir gets reeaaally hot but the one at the bottom is cold.
i flushed the radiator out and i dont know what else to do.


any ideas?

 

[btmaldon]

Before you do anything expensive try changing the expansion tank cap for a new one. It sounds like you are loosing pressure which will stop the coolant circulating.

This would leave hot and cold spots in the system and cause it to overheat. It may also have been the cause of the head gasket going in the first place.

If this doesn't cure it, you may be looking at a knackered water pump.

Best of luck.

 

[Daleyboy10]

cheers for the help.

i replaced the water pump only a coupe months back. ill try the other stuff that you suggested.



Dale

 

[Chas Uno]

The top hose takes heated water from the engine into the radiator where it is then cooled, then taken back into the engine via the bottom hose to the water pump. Therefore if the top hose is hot and the bottom hose is cold it sounds like the radiator is blocked or you have a massive air lock in the system. One other possibility is a failed water pump than is simply not circulating coolant around the cooling system.

If your radiator fan is not coming on then that may cause some of the symptoms you describe though I'd have thought the bottom hose would at least be warm rather than cold. There is a simple thermostatic switch on the radiator that operates the fan. Check that you are getting a current to this switch and also check that the earth is indeed earthing. I had problems with the earth connection on my 70SX (the female spade connector, black wire, that connects to the multi earth block aka 'hedgehog') that just needed a good clean back to bare metal.

You said you'd changed the gaskets? I assume you mean the head gasket? Did you have the head skimmed or checked for trueness?

I'd suggest checking the radiator again for blockages. Try reverse flushing it. Also, did you bleed the cooling system after (I'm assuming) you changed the head gasket? And check that the water pump is indeed pumping. What may be happening is that the fault that caused the gasket to go in the first place is still there. You need to eradicate this else you could end up with another failed gasket.

Lastly, check the timing. If this was disturbed during the head gasket removal it may be too far advanced, which can cause overheating. Check it and reset it dynamically with a strobe if necessary.

Good luck and let the forum know how you get on

 

[Daleyboy10]

ill try some of your advice and check the water pump and re flush the radiator.

and for the gasket yes it was the head gasket and we thoroughly checked it if it needed skimming at all and it was fine.

i will inform you when i have found the problem.

Cheers
Dale

 

[Daleyboy10]

i have sorted the problem with the car.

turns out the radiator is fine it was the thermostat which was buggered.
fitted it and now the fan comes on and no overheating

Dale

 

[btmaldon]

Glad to hear the good news.

Its strange how things decide to play up following one problem.

 

[alexGS]

Yes, thanks for the update Interesting that a thermostat failed in the closed position - I haven't seen that before.

-Alex

 

[rawill]

Yes, thanks for the update Interesting that a thermostat failed in the closed position - I haven't seen that before.

-Alex

Not common, but about 4 years ago I had a thermostat the kind of slipped a gear and started opening and closing at higher temperatures than designed for. I found it after putting on a new fan, cleaning out the already clean radiator.

I couldn't figure so I tested in a pot on the stove with a thermometer. I was surprised to say the least. This was on a 92 Mazda Astina.