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MG MGF Technical - Coolant loss - is it an HGF? - yes it is - no it isn't

OK, here's the story about my Feb 1998 VVC currently at 45,500 miles.

Some coolant loss over a long period of time and what I thought was a worsening situation. No mayo on dipstick and no obvious leaks. So I decided to have my local MGR dealer pressure test the system.

Conclusion: no external leaks and MOT emissions sniffer indicating some signs of combustion gases in the expansion bottle. Hence HGF.

Not wishing to invest in 6 hours plus labour to be sure of this I asked Tech-Speed for some advice. They have looked after the car well since it's move to the darkside, over a year ago. Get a chemical test says Roy Forde.

So my local garage (not an authorised dealer of anything) have a chemical test and for a very reasonable £11 pronounce it negative. No HGF they say, adding "Have you considered a small weep at the water pump that boils off the coolant leaving little sign?"

So back to the MGR dealer and after some conversation about how much coolant loss I may have had, we agree that it is possible for there to be a leak around the water pump that would not show.

So, check back with Tech-Speed and Roy agrees the water pump theory is definitely possible. He says that small weeps that are difficult to trace are not uncommon.

So the moral of the tale is - not to leap into HG replacement on first advice and take as much advice as possible.

However, I still have some concerns, as there are other niggles around fast idling and radiator fan coming on too frequently - I'm changing the engine temp sensor today as it logged a fault on testbook. Also replacing the expansion bottle cap just for the hell of it - total cost of sensor and cap is less than £20. I also need to keep checking the oil for mayo as I could just have spotted this coolant loss very early and of course I haven't driven the car much since.

If I fix the idling issue and get no mayo, then I'll go for checking the water pump. Labour to remove the covers will be worthwhile to change the cam-belt as this would be due in about 6 months anyway.

Anyone else got any thoughts?

Dave
Dave

Dave
I guess you've checked the area(s) where you park the car for drops of coolant, and this is negative. When the engine is stopped, the coolant system is still under presssure, so leaks should be visible.
The water pump theory sounds good to me, the coolant would probably not be visible from here, the pump may also be ineffecient, or damaged which may explain your other observations. Replacing the coolant cap is also a good precaution as it may be losing small amounts through here (should be visible on the reservoir though).

If water is going into the engine, then the gasket doesn't hold out for long and it soon becomes painfully obvious, so HGF doesn't seem likely.
Sounds to me like you've got it well covered.

Good Luck!
Steve
Steve

Steve,

Thanks for your words of encouragement. There definitely have been no obvious leaks. I park on white concrete and it would have been obvious.

I haven't put many miles on the clock since having the pressure check, so I'm still very vigilent. But, crossed fingers, if nothing else happens I'll wait for the opportunity for Tech-Speed to check out the water pump.

Dave
Dave

Check under the carpets in the front footwell, driver's side. You will need to lift the carpet to make sure. Sometimes the hose clipped joints by the heater and control valve weep. It's no use just pressing the carpets because you can have a tremendous anount of water under the carpets before you feel the wet on top.

Just a thought

Bruce
Bruce Caldwell

Thanks for this idea Bruce. Have checked it out and all is dry.

Situation update:

This afternoon I replaced the engine coolant temperature sensor and the coolant expansion bottle cap. The idling issue I mentioned previously immediately dissapeared. So I checked out the radiator fan operation (also previously mentioned) and it seems to be fine also. After 20 mins idling the fan cut in and after a few mins of fan operation it cut out. When it first cut in, I checked under the bonnet, above the rad, with my hand and it was certainly hot.

After topping up the coolant to the correct level I went out in the lanes of leafy Bucks and got the oil temp up to 120. Whenever I had to stop during the run, the engine idled perfectly. On my return I let the engine cool and checked the oil. Still no mayo.

So, all looks much more promising than previously. I'll carry on driving normally and be vigilant with the coolant level to try and assess just how much loss may occur. Then, I'll get Tech-Speed to take a look at the water pump and change the cambelt whilst they're at it.

Sounds like I have a plan.

Dave
Dave

Dave, your car is also absolutely the right age to start having problems with radiator corrosion and leakage - plus all the other sources of potential leaks that are well known about (underbody pipes etc).

Best to ensure that these items are thoroughly inspected (which in the case of the radiator, will involve removal of the front bumper).
Rob Bell

This thread was discussed between 19/07/2002 and 22/07/2002

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