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MG MGF Technical - Coolant Loss from Expansion Tank

Last week completed 250 mile no coolant loss from expansion tank?This week 25 miles topped up expansion tank twice,once one and half pints,then one pint.
I have an expansion with a low level alarm fitted so i have been able to stop and fill up.
Also notice the coolant water has an oily feel to it.
Please can anyone help with suggestions and advice.
J.W Critchley

Can u get the car up on ramps to check that all your coolant pipes are intact. Coolant loss is a scary thing, it happened to me when i had the dreaded hgf.

Unfortunatley if u are losing coolant from the expansion tank the sign of oil in the water is harder to see.

Try a few miles after a top up and check for mayo in the expansion tank.

Good luck i hope you get it sorted out.
r davis

Old coolant can be oily - and what's crucial here is that there is no water/oil emulsion (the classical "mayo") - assuming that the oil itself is in good condition, then there isn't any reason just yet to fear HGF. But unless the coolant loss can be identified, then there is a clear risk of HGF.

Aren't these low-coolant level alarms wonderful? It'll almost certainly saved your engine so far! I know it's saved mine when the water pump started to leak profusely.

Plenty of suspects when looking for a coolant leak. Hoses can weep at joints or split (although under these circumstances, the water loss tends to be pretty rapid). The raditor corrodes and fails. The underbody coolant pipes corrode where the mounting brackets are welded to the pipework and leak. And the coolant/water pump can fail, leading to leakage (easiest to look for this with the offside wheel and cam cover removed).

Happy hunting!
Rob Bell

Thanks for both your replies,very much appreciate.
I will have to do some more checks before jumping to the dreaded HGF,only hope its a leak from somewhere?
Regards,Walter
J.W Critchley

UPDATE ON COOLANT LOSS.
Unable to find any leaks from loss of coolant,i have ran the car for approx 25 miles today with no coolant loss?
Decided to face the HGF question,took the car to a local engine repair garage,and the owner mechanic inspected the expansion tank when hot,he also tested the system by removing the expansion tank cap and placing a glass tube tester filled with some blue coloured liquid,he said it would turn yellow if the HG had failed(sorry dont know what the instrument was called)has anyone got knowledge of such a test or instrument.
Anyway the liquid DID NOT ALTER.so he said the HG had not failed?but to monitor the oil level and expansion tank water level over the next few days to see if any more incidents of coolant loss.
Again would appreciate any advice on the subject.
Regards Walter
J.W Critchley

Great news - and just wondering now about the coolant pressure cap? These can start to fail and vent vapour under pressure, leading to falls in the coolant level...
Rob Bell

I think that test would come under the term 'Sniffer test', where the coolant is tested for the presence of hydrocarbons i.e. the product of the combustion process. As Rob says, there are plenty of places that coolant can escape without necessarily being visible until you look quite closely. In my experience the most likely place a leak that appears to have a variable rate of fluid loss would be either the radiator or the water pump, but it would be wrong to expect a leak from anywhere to be fixed at a constant rate.
bandit

Thanks again for the info,the expansion cap came with the new sensor alarmed expansion tank i fitted last October,MGF has spent most of winter in my garage apart from turn over run over winter.
But i have another pressure cap from my previous expansion tank i can try this one ?
Regard WALTER
J.W Critchley

Yes, try it and see :o)
Rob Bell

Losing more than 2 pints in 25 miles would make me fairly sure the coolant is escaping as a liquid, rather than vapour. Check around the expansion bottle for evidence of coolant having seeped out of the cap - it will leave a coloured residue as the water evaporates off. Certainly worth seeing if an alternate expansion cap makes any difference.

Both times I've detected a leaking water pump has been on an F that had recently emerged from a long period of hibernation. Due to its position on the engine the coolant that leaks out will mostly evaporate before it reaches the bottom of the car so you'll only see a drip appearing under the car if the leak is quite severe. Even if it's all evaporating there's usually some coolant-coloured residue visible in the bottom of the timing cover, which you will see if you remove the rear driver side wheel and unscrew the closing panel in the wheelarch.
bandit

Thanks Bandit i will check that out,it does seem as though losing so much liquid it must be a leak.And the previous weekend i had completed 250 miles without the lost of coolant from the expansion tank?
Yet this weekend just gone 25 miles and the expansion alarm goes off twice,hence 2 pints of liquid replaced.
J.W Critchley

Hello All.

I've used my MGF quite infrequently over the winter - 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 my dipstick. Needless to say, with a combination of some 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 or some coolant may simply be venting off and the mayo on the dipstick could be just condensation building up on account of infrequent use. Anyone else had similar?

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.

Any comments would be greatly appreciated.

Thanks

Mark
M D Allen

Mayo specs could simply represent some condensation after lay up, and are frequently found if looked for.

Small changes in coolant level like this could mean many things - ranging from nothing to worry about, through a failing coolant pressure cap to whole hog head gasket failure!

I wouldn't be in any hurry to write off the head gasket at this stage Mark.

Certainly worth checking that the system has been properly bled (check yourself, it's all pretty simple) and keep an eye on things. A new cap costs just a couple of quid, and might be a worthwhile investment at this stage, as chances are, yours will be pretty old - and all caps fail eventually.
Rob Bell

Thanks Rob

I went for a quick drive up to the coast and back last night (about 20 miles). When I arrived and parked up I checked the coolant and oil and noticed a small drop in coolant level from what it was when I set off and some traces of mayo on the dipstick that was not evident before setting off. I wiped the dipstick, we went for a walk down the beach, and set off for home. Once home I carried out the same checks and the coolant level had dropped no further and there were no signs of mayo on the dipstick. I suppose my fear is that there could be some minor breach of the headgasket only active when the engine is properly cold i.e. for the first few miles setting off from home. After the initial warm up and the engine "sandwich" tightens the minor breach is clamped shut - hence no signs of coolant loss and mayo between the coast and when I return home. This sort of pattern with coolant level/mayo has repeated itself on a number of occasions.

Anyway, I've booked the car in at MG Mecca just 15 miles or so south of Norwich - very friendly people - and they are going to carry out a diagnosis for me this coming Friday. Whatever they come up with I suppose upgrading to the MSL gasket won't be a bad idea anyway - unfortunatley, I'll be about £800 lighter. Oh well, that's part of the joy of MGF ownership, I guess.

Kind regards

Mark
M D Allen

Thanks Rob

I went for a quick drive up to the coast and back last night (about 20 miles). When I arrived and parked up I checked the coolant and oil and noticed a small drop in coolant level from what it was when I set off and some traces of mayo on the dipstick that was not evident before setting off. I wiped the dipstick, we went for a walk down the beach, and set off for home. Once home I carried out the same checks and the coolant level had dropped no further and there were no signs of mayo on the dipstick. I suppose my fear is that there could be some minor breach of the headgasket only active when the engine is properly cold i.e. for the first few miles setting off from home. After the initial warm up and the engine "sandwich" tightens the minor breach is clamped shut - hence no signs of coolant loss and mayo between the coast and when I return home. This sort of pattern with coolant level/mayo has repeated itself on a number of occasions.

Anyway, I've booked the car in at MG Mecca just 15 miles or so south of Norwich - very friendly people - and they are going to carry out a diagnosis for me this coming Friday. Whatever they come up with I suppose upgrading to the MSL gasket won't be a bad idea anyway - unfortunatley, I'll be about £800 lighter. Oh well, that's part of the joy of MGF ownership, I guess.

Kind regards

Mark
M D Allen

This thread was discussed between 17/04/2010 and 12/05/2010

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