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MG MGF Technical - Where does coolant disappear ?

After an intensive ride with my 98 build VVC I noticed that sweet smell of coolant. The temp gauge quickly approached the red level but I managed to stop the car immediately so I am quite confident it did not overheat. The engine bay was sprayed by coolant. I waited for the car to cool down and refilled the expansion tank. The car used approx. 3ltr on a 40-50 km distance, I always refilled when the temp. gauge started to move above medium. It is now in the garage but I can see no leaks as the garage floor is dry. Checked the radiotor fuse and it is ok. So is this HGF or not ? Where did the additional water go ? Is it safe to restart the engine to check if bubbles can be seen in the expansion tank or will I risk a complete blow up because water filled the combustion chamber ?

Thanks for your help.
Oliver G

Oliver,

> >The engine bay was sprayed by coolant

> >It is now in the garage but I can see no leaks as the garage floor is dry

These are not so contradictory as you might think. If there is a split in a coolant hose (e.g. the main engine outlet hose, which is only visible with the engine cover removed) then it's possible that coolant only sprays out when under reasonable pressure from a hot engine.

I've had such a split that lost no coolant when driving with low revs at a consistent speed that produced a good cooling flow of air through the radiator. But, in slow moving traffic or idling the engine got hot, the pressure rose and coolant sprayed around. At this point you could see drips running down the engine bay on to the ground.

HTH

Dave
Dave

I would agree with Dave, unlikely to be HGF, a split hose, or even the tank itself is a likely suspect but it will be well worth your while to replace the expansion cap regardless.

Get the garage to perform a pressure test, any leak will soon become apparent.

Tim
tim woolcott

> >The engine bay was sprayed by coolant

Actually, if you noticed this easily and it's all over the front of the engine bay around the expansion bottle area then Tim's suggestion of the faulty expansion cap is more likely than a split hose. Failure of the cap is a common problem, probably more so than a split hose. The engine outlet hose, when split, will tend to spray all over the back of the engine bay i.e. the bulkhead with the cabin.
Dave

I agree with you guys - the expansion tank cap is by far and away the most likely culprit here.

replace with new (it costs a couple of quid) - this sould solve the problem. It's happened on my car in the past...
Rob Bell

I hope it is only the expansion cap but after cleaning the top of the engine I had to refill it 4 times and the engine bay remained clean. I will check if the radiator fan is working but if it doesn't I still don't have a clue where the coolant went. If the fan doesn't work will it just evaporate ? I remember looking beneath the car with the engine running the first time I refilled and there were no leaks or coolant dropping from somewhere.

cheers
Oliver G

> >If the fan doesn't work will it just evaporate ?

No, if the radiator fan doesn't work the engine will overheat and over pressurise the coolant with the likely result of the head gasket blowing.

Start the car and let it idle. The radiator fan should kick in after about 20-30 minutes (from a cold engine). Whilst waiting for this to happen, keep checking the engine bay and under the car for coolant leaks. Also keep an eye on the temperature guage. Be prepared to shut off the engine if the temperature gauge strays anywhere above it's normal position or you begin to get leaks/steam from anywhere.

If you do have an external leak (and the amount of coolant you have used suggests a significant leak) then you ought to see something.

If you don't then the water is disappearing inside the engine due to an HGF, but this doesn't tally with your earlier description as you'd have oil/water mix (mayo all up the dipstick) or some running difficulties.
Dave

>>I hope it is only the expansion cap but after cleaning the top of the engine I had to refill it 4 times and the engine bay remained clean.<<

Oliver - was the engine cold and switched off when you were topping it up with fresh coolant???

If a HGF, then water can flow out of the cylinder head and onto the hot exhaust manifold and instantly evapourate - which may mask the initial water loss.

The way to look for this is while the inspection cover is off, start the engine, and look at the right front corner of the engine. If you see ANY water in the vicinity of the exhaust manifold, then I am sorry to report that this is a HGF.

Secondly - you may have a considerable amount of air in your cooling system. I highly recommend that you bleed the entire system otherwise there is a potential for airlocks to wreak havock to your engine... :o(

Good luck
Rob Bell

Hi Rob

engine was hot when I had refilled it. I will check the exhaust manifold as you recommended. Honestly I also think that it is HGF. If it is any recomendations as to what should also be changed or done as the head is off anyway.

Oliver G

> >If it is any recomendations as to what should also be changed or done as the head is off anyway.

Head porting? ;-)

Dave

You should definitely check:

* head's hardness - a soft head is scrap
* head's flatness - it's likely to need skimming to ensure it is flat
* length of stretch bolts securing the head
* other damage to valves, valve springs etc.

You should deinitely use:

* latest gasket
* latest steel locating dowels

If oil/water HGF, clean out all gunk thoroughly and change the oil 500 miles or so after the rebuild.

Take care when reassembled that all air is bled from the cooling system.

I've probably missed some stuff. Rob will be along soon!


Dave

Yup - I agree Dave :o)

The list we discussed when your head gasket first failed is found here: http://www.mgf.ultimatemg.com/hgf_pages/HGF_checklist.htm

So that adds things like changing the coolant type to the low-maintenance OAT type and various checks to other items such as inlet manifold gaskets and condition of bolts etc.

Replacement of the expansion tank cap should be replaced as a matter of routine during head gasket repair.
Rob Bell

The volume of coolant in the system is appoximately 10 litres. if you lost 4 litres the system is pretty low. There will almost certainly to an airlock in the system somewhere after filling.

I am in two minds whether this is any more serious than a water leak. My gut reaction would be to say no it is not a HGF, but only by following Rob's advice will confirm this one way or the other.

Not really wanting to add to Dave and Robs list of things to check when fixing a HGF: check all the hydraulic followers, if they are warn change them. As far as stretch bolts go I would replace them any way and ensure the garage know how to tension them correctly.

Tim
tim woolcott

>>> The engine bay was sprayed by coolant. <<<

This one tells me it isn't the coolant cap. But I am not that technical, so...

good luck
Erik

I've also been losing coolant over the last six months or so. I've had the system pressure tested and I was told that it was OK - held pressure overnight. However the cap failed the test and a new one was put on. The car doesn't get used on a daily basis so it's sometimes difficult to tell how much coolant it is using. Anyway last night I checked oil and water before the CSMGF Run today and noticed the clip on the hose that goes into the top of the expansion tank was wet. On further investigation I found the tank was lose and some antifreeze residue was on the panel beneath the expansion tank. By the way, the hose clip was very slack - I could squeeze it open with my fingers. What I think has been happening is that the tank has been moving and occasionally the seal at the hose has been broken which allows a small amount of coolant to escape. I tightened the tank and fitted a new clip and during today's run I've had no problems.
David Clelland

Thanks to everybody for their comments. The car was at the dealer y'day and they found no signs of HGF. The cause was the expansion cap so I was lucky to have recognized the coolant loss so early. I had coolant replaced in order to make sure that no air locks remain. Hopefully they did it correctly.

cheers
Oliver G

This thread was discussed between 19/08/2003 and 26/08/2003

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