Engine running hot - coolant at 100+

**S2TORNADO** · 9 June 2012, 15:33

air lock in system?

**Sleeper_Avant** · 9 June 2012, 15:37

when its cooled right down just check the water level again, might have just had a hissy fit when it was sick,

then if thats ok, just keep checking all the hoses as its runnning and each corner of the radiator to make sure theres no cold spots, the system may well still get hot even if the water is not circulating corretly, if that makes sense

what condition is the radiator in? if you can keep the temp down with the heater fan on full pelt then its a circulation problem more than likely

**prj** · 9 June 2012, 17:25

Are the coolant hoses hard?
Head gasket?

**MarkT** · 9 June 2012, 17:36

I have just gone through the same scenario albeit with my golf tdi.
It was the head gasket.

**cooperquattro** · 9 June 2012, 17:37

Only thing I did notice is the radiator is alot cooler to the touch at the bottom than the top,

thermostat is stuck closed

**Tony Stark** · 9 June 2012, 17:38

Originally posted by prj

Are the coolant hoses hard?
Head gasket?

Mine was the same i discovered a few weeks ago, although the weakest point it found was the main rad, hoses used to be firm when i first got it, rad replaced they went hard. Checked the spark plugs and found one was orangey in colour then did a chemi-test and the fluid turned very quickly comfirming a failed gasket.
Temp was always fairly good though.

If your still having probs after a good system bleed id change the stat and finger the hole in the block to make sure the pump impellar is intact and not freewheeling on the shaft.

**europeanme** · 9 June 2012, 17:57

Originally posted by S2TORNADO

air lock in system?

mine did the same when I put a 2nd hand rad on my avant....the fan finally kickied in around 90+4....way to hot.....

how old is the rad?...

cheers
Mike

p.s. have you spoken to either of the Paul's?

**Rocco** · 9 June 2012, 18:29

This is normal here in summer

**andyg plym** · 9 June 2012, 18:33

Originally posted by Ross

Any ideas guys?? This started with overflowing coolant from the header tank, drastically so - like losing 5l of coolant on a half hour drive...

Today a new coolant header cap was fitted which stopped the coolant leak completely. It's holding pressure nicely now!

However - the car is running too hot, in traffic I'm seeing 90+3 to 09+4 at which point on put the heating on full blast and put the windows down, which held it steady at that. Usually it would stick between 90 and 90+1 with the fan tripping in from time to time. On cruise it's steady on 90+1 with the fan constantly running on speed #1 - usually it would be 1/2 notches below 90.

The radiator is getting hot so I don't think the 'stat is stuck - and when the fan kicks in it is effective - it's almost like the coolant flow is restricted or something. Water is circulating back to the header tank, and it's getting heat to the cabin. Only thing I did notice is the radiator is alot cooler to the touch at the bottom than the top, but then the fan is kicking in at the right temps as per the guage and the temp sensor for the fan is at the bottom right?

Any ideas? I'm stumped

ross,

had exactly the same 2 weeks ago when i had to replace that small hose going to thermstat housing,while i was there i replaced the stat too and also replaced the fan cowling.
exactly the same,i filled it with water and made sure there were no airlocks etc,temp would go to 94 on the gauge and the fan refused to cut in,sorted that but then still happened,put a new cap on and all is well again

**Ross** · 9 June 2012, 20:00

Thanks for the comments guys, I have a few things to try, namely bleeding it ensuring no air locks and checking the hoses and stat. The eruption from the expansion tank started before it was even up to temp which does suggest pressurising from the cylinders, I am bracing for the worst to be honest but I think I need to rule out potential causes that don't involve lifting the head again! After that check plugs and compression test I guess.

The rad was replaced dec 2009 and water pump and stat last summer.

@Mike - I've spoken to the Paul's and will give you a shout. I'm having those front discs as spares and will order the rears too.

**4WheelDrifter** · 9 June 2012, 20:24

Does the coolant tank pressurise after running the engine for just a few seconds?
It would be unusual for a stat to fail in the closed position. But you can check as it warms up, if the heat runs through the heater hose or the radiator top hose.

**prj** · 9 June 2012, 21:28

Please be very careful about this.
Take off the plugs and inspect each cylinder visually.

**Ross** · 2 October 2013, 13:10

To tie up this thread - the overheating problem was a clogged radiator. It looks like, at some point, probably a mix of coolant types has caused gunk to collect and I guess since the rebuild it's got worse.

With the MFTS not returning a signal I was not aware, as the dash gauge was not working. I only realised when the coolant was lost due to a cap failure and it boiling over.

I've replaced the thermostat out of caution (old one was opening though), checked vanes on the water pump (it's fine) and replaced the radiator following a full flush of the cooling system.

Today I struggled bleeding the coolant as I can't get the fan to come on with it idling, it happily rises to 87C on the gauge at which point the stat opens and it stays at 90 or a notch below. Had to give it some revs to get it above, and it quickly settled back down.

Case closed I think

**Error404** · 2 October 2013, 15:32

A job well done mate

Engine running hot - coolant at 100+

Engine running hot - coolant at 100+

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