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MG MGF Technical - Minor problem/Major problem? (Coolant)

Hello All.

I've used my MGF quite infrequently over the past three or four months - probably only once a week at the most. I had my coolant flushed and changed by a local, well established garage in January - he seemed familiar with the MGF, but, I don't know that he attended to each of the coolant system's three bleed nipples during the refilling process. Since January I've covered only about 600 miles but am finding myself having to top up with 5mm or so of coolant every couple of weeks to bring the coolant up to the coolant bottle seam level, but having said that, the coolant level never drops below "minimum". Also, I've been getting some small deposits of mayo on the oil dipstick. Before the coolant change in January, the coolant level was rock steady at the coolant bottle seam level and I don't recall any signs of mayo on the dipstick.

Needless to say, with a combination of some apparent drops in the coolant level and some small deposits of mayo on the dipstick I've been fearing the worst (HGF). However, trying to be positive I imagine what appears to be some coolant loss could I suppose still be the cooling system self bleeding any residual air locks since the coolant was changed. Perhaps some coolant may simply be venting off and the mayo on the dipstick could be just condensation building up on account of infrequent use during the past few months. Anyone else had similar experiences?

A few notes - the car runs very sweetly, temp and oil gauges are all as they should be, no visible signs of water leaks or steam and have had the coolant system inspected twice by local garages since January - no leaks identified. No signs of any film of oil in coolant and no mayo under the (newly replaced) coolant bottle cap or oil filler cap. When I clean the dipstick of the small deposits of mayo and re-dip, the oil in the sump shows no signs of contamination and is very clean. The car's head gasket was replaced originally at 15K miles (just outside of warranty - I bet the previous owners were well pleased) and the car is currently on 35K miles, 4K miles of which I've done since I bought the car last June.

Any comments my car's recent coolant level/mayo experiences would be greatly appreciated.

Thanks

Mark
M D Allen

Its quite possible that if the system is not perfectly bled that gradually any trapped air will work its way up to the coolant bottle. Am sure you appreciate its important to ensure you have sufficient coolant in the system - your 5mm above the seam is perfect.
The mayo you refer to can happen if you only do very short journeys, when the engine never gets really hot to boil off any condensation in the oil. Having had the system pressure checked should prove all is OK, but whatever happens ensure you have water in that bottle as the engine has a very small water capacity and can quickly overheat causing much more damage than a HGF.
To help matters make sure you only use light throttle and keep engine below 3000rpm until the OIL TEMP gauge is up to temperature, this takes about 6-8miles from cold and makes sure all those long bolts are tight and the alloy engine components have expanded - then you can let rip!
Check the level every trip or get a low level alarm - just make sure there is water, until you really have proper mayo - then worry.
Pete
Pete Tipping

Agreed, the fact that the coolant level was static before the change in Jan does make imperfect bleeding the most likely cause. With no sign of oil mixing with coolant, and only slight mayo, I'd be inclined to give the gasket the benefit of the doubt until there's a material change in the behaviour.

Perhaps a worthwile exercise would be to do a follow-up bleed of each of the 3 bleed points, re-set the coolant level in the expansion bottle, and over the next few weeks only top-up from one 2l bottle of water so you have an accurate measure of loss rate. When checking the oil, use a white kitchen towel to absorb the mayo and leave to dry; if the mayo is a result of coolant not condensation there is likely to be colouration visible once the water element has dried off.
bandit

Many thanks to both of you.

Very helpful/informative and some excellent tips concerning filling only from the one fixed capacity bottle and looking for coolant colouration on the white paper towel.

I'll take all your comments on board, keep a close eye on things, attempt the follow up bleed myself this weekend and then hopefully the coolant level will re-stabilise in due course.

Best regards

Mark
M D Allen

Performed the bleed last night - don't know that I expelled all that much air but it must have done some good as following a 40 mile round trip up to the coast last night the coolant level appears to have regained its composure.... and whilst there are still some traces of mayo on the dipstick, at this stage, I don't have reason to be over-concerned by this. (most likely condensation on account of infrequent use and the white paper towel test revealed no colouration from the pink OAT coolant).

Thanks again for your advice.

Mark
M D Allen

That's encouraging news, long may the stability reign...

The oil filler cap on the cam cover isn't exactly easy to get to, but opening it for a few hours after a run might speed up the evaporation of any moisture in the oilways.
bandit

This thread was discussed between 26/04/2010 and 29/04/2010

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