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MG MGF Technical - Coolant Loss

I'm 'losing' coolant from my 2003 (MY04) TF160.

There's no oil in the water, nor any water in the oil. No team from the exhausts, and the temperature gauge is rock solid at just below halfway. There are no obvious leaks (I've had a good look). The cambelts were done a week or two ago and there was no sign of leakage from the water pump. I've replaced the cap.

Coolant was changed at major service a few weeks ago (same time as the belts).

Was thinking it must be goig into the engine, but have been on holiday for ten days and the coolant level has dropped about a quarter of an inch... No puddle underneath, but then again it is a very small amount and the car is outside on the drive.

I was thinking of an airlock; I've had the plastic heater cover off this afternoon and don't reckon it has been moved in years... Which would indicate that the system wasn't bled properly. I haven't tried bleeding the heater yet, but coolant comes out of the radiator bleed when I open that.

I've run the car up to temperature on the drive. On of the underbody coolant pipes is hot, one cold. The car has a PRT as standard. Has aircon, although I cannot see that makes any difference (I need to check the manual carefully though).

Any ideas anyone please?

Thanks,

Neil
Neil

sadly this does sound head gasket like :(

if so expect to find a small amount of coolant on top of the alternator, but being so close to the exhaust this will evaporate off
Will Munns

Not necessarily so sad Will, the car is under warranty from a Renault main dealer...

But not necessarily gasket either. That's too obvious, and the conclusion everyone jumps to.

My post is not so clear! When I say I went on holiday, I meant that to show that I didn't use the car.... ie the coolant dropped without the engine running. And that would be a monumental head gasket leak!!!

I'm hoping for some other suggestions???

Neil
Neil

Sadly that doen't rule out HGF. Mine only leaked when the car was cold (the head is clamped more firmly when the engine heats up)
Will Munns

Air temperature and pressure also affect the coolant level to that extent. Maybe nothing more than that?
Charless

So many things it could be, without it being the head gasket gone. However, if you don't find the cause of the leak and fix it, it will undoubtedly lead to the head gasket failing.

After topping up, has the level dropped again? If not, it could just be an airlock caused by the coolant change. If it has dropped again, then the best bet is to get the cooling system pressure tested.
Ralph Gadsby

Whilst what Ralph says is true as far as HGF, he ought to know, pressure testing is no guarantee of finding the fault.

Inlet manifold gasket and rubbish plastic radiator bleed cap are frequent causes of small fluid losses. The former even when the car is stationary.
Aging underfloor pipes are another area worth looking at. Of course you would normally expect to see the drops on the ground, but we had a similar problem a while back without, so it's not certain.
D

I'm confused about one of the underbody pipes being hot while the other is cold. That's why I'm thinking about an airlock???

Neil
Neil

well it is the radiators job is to make the coolant cold :)
Will Munns

Have all bleed nipples been opened/bled after coolant change. Apparently this is a common oversight when servicing/changing the coolant and does lead to some problems. I'm sure someone will correct me but I believe there are three in total, (though my garage insists there are only two - hence air locks, incorrect flow and evaporation occurs - which can eventually lead to HGF).
Dez

As Will says, the right hand pipe will be cool, as it contains the water returned from the radiator - the left one will be hot as this carries the coolant from the engine.

Your TF is now entering the age range when the under body pipes start to fail - typically corrosion around the mounts eating from the outside in. I might reasonably expect to see a coolant residue under the car though, but the leak may be so slow as to not result in a 'damp patch' under the car...

Another 'classic' area for a slow coolant leak is the water pump. Annoyingly hidden behind the plastic cam cover, buried deep in the engine bay. Not exactly the work of a moment to inspect.
Rob Bell

The right hand pipe is cold, not cool. The radiator will only drop the temperature 10 or 20 degrees, particularly with the car stationary.

I read in the workshop manual that you are supposed to fill the expansion tank "to the brim" AFTER bleeding, run the engine, and then top up "to the MAX mark" if necessary. That would imply that bleeding does not fill all of the air voids...

So it could be that there still isn't enough coolant in there (the rate of loss is reducing).

Is it possible/feasible to get at the third bleed nipple without removing the engine cover? Obviously I don't want it to be so difficult as to take longer than removing/replacing the cover though!

Thanks,

Neil
Neil

Very very difficult. I'd suggest that removing the inspection cover is a doddle in comparison and with the cover removed, access to the third nipple (all very Scaramunga this talk of third nipples) is straightforward.
Rob Bell

Another trick is to jack up the front of the car while bleeding the system and dont let the reservoir empty whilst filling it. This takes two people as one needs to be in the bonnet area taking care of the bleed nipples.
The third nipple doesnt usually need to be bled unless you have a problem with it not bleeding using the other two. I also had a car that so badly airlocked that I drained the system and started again.
Simon Wilkinson

Three nipples(A,B,C) AND a jiggle valve(D) to check:-
http://www.mgfcar.de/bleed/index.htm
If Scaramanga is about, niknak can't be far away.
Charless

The Head Gasket Failure is usually a result of a component failing in the coolant system as the HG is the weak point of the K series engine. I tend to find on any car running this engine that the HG replacement is always married with another component needing replacement. e.g. 3 Weeks ago bought 2000 model MGF for £1000 from a local dealer with HGF, when I got the head off it had already the new 3 part HG which hadn't been in there that long, also a shiny new water pump and radiator. The reason for the HGF occuring again was a knackered inlet manifold gasket and one of the two O rings on the thermostat housing. For the sake of a few extra quid the last owner/garage could of replaced the lot and as you all have said before a decent bleed (leave the cap of the expansion tank overnight and then retop up after bleeding is something I always do) would be good for probably as near as damn it the life of the car.

I have now done something like 20 HGF on this engine type in 3 years on various Rovers/MG's and now as a matter of course I change the thermostat and two O rings on the thermostat housing, the water pump, inlet manifold gasket, of course the timing belt and check the fins on the radiator especially at the bottom(replace if required).
Tim Martin

Am slowly but surely narrowing down the problem...

The coolant level is hardly dropping at all now. There is a coolant smell in the car when the heater fan is on. Doesn't seem to make much difference if the heater is on hot or cold. There are no 'obvious' leaks from around the heater, so I'm wondering whether the smell is actually coming from the radiator through the front bonnet-space (no idea what you call it!!) and into the heater. I'll need to get the bumper off to check the radiator. Also might try blanking off the heater air inlet.

Thanks for comments everyone.

Neil
Neil

This thread was discussed between 19/04/2009 and 14/05/2009

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