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Re:Overheating

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16 Aug 2019 08:21 #212155 by GWFBrown
Re:Overheating was created by GWFBrown
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

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16 Aug 2019 08:57 #212156 by CC Baxter
Replied by CC Baxter on topic Re:Overheating
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

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16 Aug 2019 09:06 #212157 by Keithy
Replied by Keithy on topic Re:Overheating
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.

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16 Aug 2019 10:58 - 16 Aug 2019 11:03 #212162 by facade
Replied by facade on topic Re:Overheating
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.

If it suddenly breaks, go back to the last thing that you did before it broke and start looking there :)
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Last edit: 16 Aug 2019 11:03 by facade.
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17 Aug 2019 10:17 #212194 by Keithy
Replied by Keithy on topic Re:Overheating

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


Not a lot of people know that!
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18 Aug 2019 11:01 #212246 by RainerK
Replied by RainerK on topic Re:Overheating
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.
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18 Aug 2019 14:10 #212255 by facade
Replied by facade on topic Re:Overheating
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.

If it suddenly breaks, go back to the last thing that you did before it broke and start looking there :)

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19 Aug 2019 09:22 #212281 by GWFBrown
Replied by GWFBrown on topic Re:Overheating
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.

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20 Aug 2019 07:59 #212355 by kirkynut
Replied by kirkynut on topic Re:Overheating
Wow, I've not heard of this one before. Well done Keithy for putting it out there!

Kirkynut

The underdog often starts the fight, and occasionally the upper dog deserves to win - Edgar Watson Howe.

My Jimny Thread Here: www.bigjimny.com/index.php/forum/8-my-ji...on-continues?start=0
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24 Aug 2019 16:23 #212625 by GWFBrown
Replied by GWFBrown on topic Re:Overheating
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.
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