Engine Coolant

[215HAN]

Hi,

Looking for advice/help again.

I this morning topped up the engine coolant with a tad bit of water. Now whilst doing a 1hr + journey on motorway I noticed that the engine coolant level doesn't stick at 90 like it did before. It' was up and down whilst making this journey but never going above 90. It drops and then goes up again and then drops but was driving fine without any problems.

Is this my fault due to adding water in engine coolant?

Please advise.

Thanks

[insanitybeard]

Highly unlikely to be to do with you adding water in my opinion. The temperature gauge on my Galaxy hardly ever rises above 90^oC, but once it's warmed up, unless it's cold and you're doing lots of slow stop start driving in town, it stays pretty stable and doesn't fluctuate. Is your temp gauge fluctuating with you driving at steady motorway speeds? If it is then it indicates an underlying problem which could range from a simple dodgy temperature sensor to a defective thermostat or water pump to a head gasket on it's way out as a worst case scenario. If you're losing a lot of coolant all of a sudden (hence your earlier need to top up with water) then I'd be careful about driving too far or too fast until you've found the underlying cause of the fault and sorted it out.

[johnnyroper]

I can't imagine it is due to adding water,I would say more likely thermostat has failed so cannot maintain optimum temp

[insanitybeard]

If that was the case though and the 'stat was jammed shut wouldn't you expect the engine to be overheating and showing more than 90 degrees on the gauge? At a steady motorway speed I would expect the engine to be working hard enough and generating enough heat for the 'stat to be fully open all of the time which shouldn't affect coolant flow or cause the gauge to fluctuate.

Not saying you're wrong, just thinking out loud here.

[215HAN]

Thanks for replying.

Yes it was pretty much steady on m'way between 50-80mph but it definitely was fluctuating and coolant level was fine, i just topped up a tad bit. It wasn't losing any coolant and don't think it is but all the way through it drove fine.

[insanitybeard]

As another test I would try driving it at a steady speed on a clear road with the heater cranked up and seeing if you can detect any difference in the temperature of the warm air coming out of the blowers when the temp gauge is fluctuating.

[215HAN]

I will give this a try but what would this indicate. Also, if it was head gasket what other symptoms would I notice

[insanitybeard]

If the temperature of the air coming out of the blowers isn't constant then it could indicate either problems with coolant flow or circulation. If it was just a dodgy sensor then it shouldn't make any difference. Indicators to head gasket problems include poor heater performance and residual pressure in the coolant header tank once the engine is completely cold, detected by removing the header tank cap on a stone cold engine and seeing if you get a release of pressure when you remove the cap.

[215HAN]

Thank you for your response. Much appreciated.

I hope it isn't the head gasket. What is cost nowadays in getting this repaired.

Thanks

[insanitybeard]

Depends on whether you're paying a garage to do it or having a go yourself. There's a few tales of the trials and tribulations of head gasket issues here (click on the topics).

[215HAN]

Thanks will do.

It's weird though as car drives fine as it did before. No issues at all.

Confused.

[insanitybeard]

The PD engines don't always show the 'classic' symptoms of head gasket failure and unless you're really pushing it you might not notice any difference in performance or drivability even if it is on it's way out. Keep an eye on the coolant level and heater operation and check for pressure in the header tank with the engine cold. Hopefully you might just have a dodgy sensor.

[johnnyroper]

When my head gasket was gone I only lost a bit of water after long motorway run due to pressure build up pushing it past the cap.

Best way to tell on a PD is give it a good run and have a feel of the rad hose see if it is hard,also can leave overnight then release cap when cold in morning to see if any pressure remains in system.

As above they don't usually show any clear cut signs they certainly don't fail a block test when gone.

After a moderate run check the temp of radiator/hose from thermostat to see if it is hot,unless it is hot outside or you have given it some stick on motorway it is highly unlikely it will be open so rad/hose should be cool.

[215HAN]

Thanks will try that also. Where is the rad hose?

Also just to add, I topped up brake fluid today too? Would this have an effect at all? Is the sensor close to the brake fluid tank? Could I have knocked it off?

[johnnyroper]

No brake fluid top up wouldn't cause it either.

The hose comes off thermostat housing at front of engine just by alternator then goes off to the radiator.

[215HAN]

Ok so drove home from Wakefield to home which is about 1 hr + drive and again noticed temp gauge fluctuating but didn't notice any drastic change in heating system. Also before setting off checked coolant level and is exactly as it was when I added a tad bit of water.

[niall]

Hi

I had this issue...not really a problem...as temp always stayed below 90 degrees.

I believe it's a common problem with VW original fit thermostat.

Problem is...the thermostat opens too early.

At varying temps below the opening temp of the thermostat which if memory serves is 86 degC...the thermostat opens allowing the coolant access to the radiator thus cooling the coolant before it gets to normal temperature hence it takes longer to reach normal temperatures. ie 90 degC.

Change the thermostat and it will come up to temp as normal.

Check out YOUTUBE for THOMASEXOVCDS..he has covered this in one of his videos..

N.