Re:Overheating

Hi everyone.
I wonder if anyone can help me - 1 have a 2010 1.3 Jimny - Car starts and runs perfectly, the only problem is, engine coolant expands into the expansion tank at normal running temperature, but does not return to radiator when the engine cools down - there appears to be no leaks - the extra coolant in the expansion tank is about the same required to refill the radiator - I have changed the radiator cap with no change in this situation.
Thanks for any help.
Gordon

If you've got the heater turned off (you probably have) turn it on full and take the car for a good run. If that changes the situation then it's on the heater loop (valves, hoses or matrix). This is agood place to start as it costs you nothing.
Chris

Check the long pipe in the expansion bottle isn't sealing against the bottom of the bottle.

If it is it acts as a non return valve....trim an inch off as they grow longer.

I'd still look at the radiator cap, there are 2 valves and 3 seals in it



1 - seals the rim of the radiator, so air cannot get into the radiator when the coolant contracts.
2- seals the top of the radiator, this is the pressure valve, when the coolant expands it lifts and allows coolant to the expansion tank
3- one way valve/vacuum break, when the coolant contracts, this allows atmospheric pressure to push coolant from the expansion tank back into the radiator.

If coolant doesn't get back, then there are really only 3 main possibilities

As Keithy suggests, the expansion hose is acting one way- I'd expect the car hoses to collapse though and air to rush in when the radiator cap is undone.

The seal (1) is missing/faulty, and air is leaking back into the radiator in preference to water getting pushed back. I'd expect to see signs of water leakage around the cap too.

There is a head gasket leak. A give away is when cold, the radiator hoses are still pressurised firm, and when you slacken the cap, you get a hiss of escaping gas.

facade wrote: this allows atmospheric pressure to push coolant from the expansion tank back into the radiator.

Not a lot of people know that!

Very, very good description!

Regarding the head gasket leak I think it should read: When the engine is cold and running (i.e., just started).

Motorbikes often have this type of cap.

My bad, I meant before the engine is started, after it has sat overnight. :blush: If you undo the cap and there is a hiss of gas escaping then it is likely head gasket.

Hi everyone.
Just a quick note.
Problem appears to be solved - one inch cut of the bottom of the expansion tank hose.
Thanks for every ones help.
Back in a few days to confirm all correct.
Regards.
Gordon.

Wow, I've not heard of this one before. Well done Keithy for putting it out there!

Kirkynut

Hi everyone.
I would like to confirm that my overheating problem has been solved by cutting off one inch of the bottom of expansion tank pipe - Thanks to everyone especially Keithy.
Kind regards.
Gordon.