Radiator Cold, Engine Stinking Hot

[Guest Sword]

Hi all, after my little endevour with the heater matrix, I finally got it all back together and no leaks. Problem is now that the engine just gets hotter and hotter, rad fan kicks in around 3/4-7/8 on the guage but the temp keeps climbing. After feeling the radiator, it is literally cold on both sides top and bottom. Do you reckon my thermostat is permantly stuck closed???

[chromedome]

You may have an air lock. Did you run the car with the filler cap off the expansion bottle until the car got hot? This should let air out of the system.

[NikpV]

Do you reckon my thermostat is permantly stuck closed

can you pop it out and test it in boiling water - I remember my dad doing that with his hillman superminx 40years ago :angry: :blink:

[Guest Sword]

I did run the car with expansion cap off. To a certain temperature anyway. But when I feel the radiator top hose, its red hot and the bottom one is totally cold. I really do think its my thermostat. Not that tricky to remove, just got to take coil pack off. But before I do this, i wanted your opinions. (just trying to find an excuse for being lazy before I tackle the problem) :blink:

[NikpV]

just trying to find an excuse for being lazy before I tackle the problem

after what you've already done :angry: :blink:

[Guest Sword]

you are sooo right Nik :blink: . Saying that, I must admit, until I purchased Elsawin and "obtained" a copy of Ford TIS, I would fear tackling anything like removing the dash for sure. But I have found great knowledge within the 2 programs and the support from here to tackel most jobs. Changing a thermostat shouldnt take more than a couple of hours, SHOULD the thermostat be the problem that is.

[El Dingo]

Silt somewhere in the system (no inhibitor, remember) has blocked the bottom hose manifold or somewhere else in the coolant path? You could try back-flushing.

 

If you have a total blockage like this you'll boil the coolant in the engine block, and this can lead to the explosive failure that you experienced.

 

:blink:

[johnb80]

Has to be water pump or thermostat.

 

Regards - JB

[Masked Marauder]

I concur, stat or pump in that order....

[tim-spam]

Normally, the stat is upstream of the top hose, so the fact that it's getting so hot indicated that the stat is probably open. I would think the most likely cause is a detached water pump impeller or a blockage / airlock somewhere.

[Masked Marauder]

Often, even with a stuck stat the top hose will get hot. Some water will always pass through the stat, otherwise when you fill the system from dry you would not get water into the radiator. Often stats have a small hole to allow for this.

[tim-spam]

The flow of water through this small bleed hole (if indeed there is one - many stats have a crude check valve that prevents the flow of water when the engine is running, and only allows air to bleed off when the engine is stationary) would probably not be enough for the hose to get 'stinking hot'. This problem sounds more like a lack of circulation or blockage.

[Guest Sword]

cripey, what do you all recommend first??

 

Should I let the car run until the rad fan kicks in with the expansion cap off in the hope I just have a airlock? Or do I just go ahead and change the stat? Are there any idiot proof guides to checking the water pump and complete circulation. I do see a trickle of water going back into the expansion tank, would this mean I have a complete circulation?

[chromedome]

That sounds like an air lock, yes keep the engine running with the cap off until the fans cut in. Increasing the engine speed can also help to "bleed" the system.

 

If this don't work then it's probably what other members have said.

[sepulchrave]

Death by RadWeld? :P

[Guest Sword]

an someone describe the backflushing procedure for me on the VR6.

[KP 115]

2 Questions

 

have you changed your coolant recently - what colour is it now

as I believe you should be using vag G12 coolant which doesn't like being mixed with other types.

[Masked Marauder]

It had no additive in, just water.....

[Guest Sword]

so I got the stat out, stat tested in a pan of water, it doesn't open at all, supposed to open at 80 C, but I left it in untill water was really boiling. So I suspect it was only the stat for now. Bought some new G12 from VW. Unfortunatley I can only get the time next weekend to install. Will keep you all updated.

[Guest Snooper601]

To reduce the risk of air locks I do the following:-

 

Fill the cooling system normally, including pumping the hoses that feed the heater, while the engine runs with the headder tank lid off

 

Next

 

Pull off the small hose that fits on to the side of the headder tank, top left looking from the front. Temporaily block the hole in the headder tank and then fit a larger bore close fitting pipe onto the hose. Keep this hose pointing upwards and then fit a large funnel on to the top of it, it must fit well with no leaks. Fill this with coolant mix but not to the top as it will probably splash and bubble a bit when the air is forced out.

 

Keep it topped up and run the engine again

 

This will give you a much higher head of water to make sure that the air that is usually trapped in the heater can escape.

 

This seemed to work for me.

 

Cheers

[El Dingo]

As a test, why not leave the stat out, re-fill with water and see if the overheating has gone away...

[sepulchrave]

Why bother, he's boiled the 'stat and it don't work?

 

It's a lot of work on the VR6 to fiddle about and do the job twice for no reason!

 

Consider fitting the Neuspeed 70C 'stat, it makes the engine and oil run cooler giving slightly better performance and MPG.

 

Get it here:

 

http://www.awesome-gti.co.uk/shop/customer...&cat=398&page=1

 

Cheers.

[El Dingo]

Well he isn't going to fit a heater matrix either...

 

And you can boil a stat to death y'know.

[Guest whiterosessom]

Will this also fit the Galaxy 2.8 v6 ???????

[sepulchrave]

I have the VR6, and I've just done the 'stat as a precaution when the housing failed, don't know if you've seen the installation but suffice to say that 'shoehorned' in does not do it justice!

 

Ok Dingo, no offence meant but I feel that in this instance Sword is right to change the thermostat, I must admit that I didn't have any problems at all with airlocking, I think that the 2.8 is largely immune to it, dunno about the 2.3 or TDi tho' :blink:

 

...and yes, whiterosessom if you have the 2.8 it is the identical VW VR6 engine.