MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Overheating MGF

A couple of years ago I had the head gasket replaced on my 98 mgf (1.8 VVC) due to repeated overheating problems (caused initially by failing engine fan). This seemed to have corrected the problem and I haven't had any trouble since, until this morning. The thermostat went through the roof and the familiar steam began pouring out of the back. However, after a minute or two of having the engine off, everything went back to normal, and was fine all the way to work (10 miles, 30 min drive with constant eye on the thermostat)

Is the head gasket likely to have gone again only 2 years down the line?
Dan Riley

Dan,

It is possible that your head gasket has failed.

However, could just be a sticking thermostat, duff sensor, faulty cooling fan, air lock or blocked radiator.

Take your pick!

Sam
Sam Murray

Dan, how much coolant was left in the resevoir?

Keep a hawkish level of vigilence - and you are going to need to find out exactly why the car over heated.

If the over heating occurred whilst sitting in sationary or slow traffic, then suspect the radiator fan - a duff water temperature sensor, a stuck fan motor or a blown fuse. http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/related_problems_overheating.htm

Other potential causes of over heating Sam has already indicated - but I'd check the fan operation first, replace the expansion tank cap second, and look at other causes third (unless there is clear evidence of water/oil mixing!)
Rob Bell

Thanks for your answers chaps

I haven't checked the coolant level or the oil/coolant mix possibility as I had to rush into work as soon as I parked. Will check before I set off (while everything still cool!)

I was actually stationary when it happened although after I turned the engine off to cool down, when I restarted and set off again, I felt the engine fan come on when I stopped at some lights. I don't suppose the thermostat could have stuck, causing the problem, and then became unstuck?

Please don't let it be the head gasket!
Dan Riley

Sounds like non-operation of the fan to be honest Dan. Top up the coolant before you set off. If the resevoir is empty, be sure to re-bleed the coolant system ASAP.
Rob Bell

Can you hear the engine/radiator fans from driving if they come on?

After mine overheated during mot they said the fans came on, but might not have checked the radiator fan. The coolant expansion tank was more or less empty after that, but have topped it up now, and is still fine after one drive.
Dan Wavell

just checked the coolant reservoir - it is bone dry!

how has that happened? do i have a leak? has it evaporated? Rob, how do I do that mate?

In case no one has noticed, I am not very mechanically minded!

Also, to top up the reservoir before i go home - is there a particular type of coolant i need can I just buy it in a garage?

Sorry lads - am worse than a woman!
Dan Riley

Dan, you can't hear the radiator fan from the passenger compartment - the only fan audible from there is the engine bay fan. You actually have to stand in front of the car to hear the front fan come on.

Okay - dry expansion tank. Not especially good news as there is now a very good chance that you've got a whole load of air into the coolant system.

Top up with normal water - the antifreeze mixture won't alter significantly unless you have to fill with more than 2 litres!

Bleeding the system is now a priority - but you are going to need access to a tool kit containing a 8mm and 10mm spanner - the latter to remove the engine inspection cover plate, and the former to undo the bleed nipples (the heater nipple is actually best approached using a socket). You'll also need to remove the radiator bleed screw - which I think is 10mm?

The procedure is simple enough - and is detailed by Dave here: http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/coolant_bleed_procedure.htm - and there are some more pictures of the location of each of those bleed nipples here: group2/suspension/suspension_images/bleed_nipples.jpg

Alternatively, call the AA/RAC and get the car trailered to your local prefered garage for a little more investigation (more expensive option, but may be better for your state of mind! LOL)

HTH
Rob Bell

thanks all for your help - I think I might take it to my MG garage!

Rob, I looked at that link and it does seem straightforward but I would be worried I was doing it wrong

One more question - if I do it myself is there a certain type of coolant i need?

Thanks a lot
Dan Riley

Oops, spotted the typo - the rad bleed nipple has a 13mm head IIRC.

Dan, it is difficult to do 'wrong' - just keep the resevoir topped up while openging the bleed screws. Also ensure that the heater is set to 'hot'. And then open each one in turn, running coolant until no more air. Tighten them all, go for a quick drive. Stop, and repeat the process.

The antifreeze type will depend on what you've currently got in the car. It is generally advised not to mix OAT antifreeze with the earlier Superfreeze3...

OAT can be orange or blue. The Superfreeze3 tends to be green. Replace like with like.
Rob Bell

Rob - top man, cheers for your help
Dan Riley

I have one last question (sorry)

Why would the reservoir be empty? Does this mean i have a leak? Or is it because of the hot weather making it evaporate? Or...?

Cheers
Dan Riley

The cap has a pressure valve - a bit like a pressure cooker. If you over heat the cooling system (as you saw on the temperature gauge) the coolant will boil, the pressure increases, and the cooling blows out as steam.

Sometimes a failed cap can result in the symptoms you saw - so it may pay to replace it anyway (costs just a few quid from your local Halfrauds store)
Rob Bell

After speaking to several people at the mg car day at silverstone numerous people were stating that a certain head gasket from a company who i will call Mi*e Satur failed after only a short while of being fitted, was yours done/from there???? if so it may be worth fitting the MGRover one again!!!!
Rick Earle

Just some notes I found when bleeding the system

Be very careful with the bleed plug on the radiator its actually plastic and so its very very easy to overtighten with a socket, so be careful

I also found the return rail even when hot gave no fluid. I had to jack up the back end and then run the engine until hot before i got fluid and bubbles, but other than that it wasn't too hard to do.

BUt I say again be careful with the platic plug, DONT overtighten
Brian Buick

There is nothing wrong with the gasket that Mike sells - and in fact if made by a very repudable manufacturer. I don't have one of these gaskets - nor do I have any interests to declare about it either.

I suspect that if the gasket has failed soon after replacement, it may have more to do with some other underlying problem - liner heights, poor coolant bleed, warped/damaged/porous cylinder head etc etc - the potential causes are many!

Fingers crossed that Dan doesn't have a repeat HGF. But an airlock now could rapidly lead to one...
Rob Bell

Dan,

In your first post you mention steam coming out of the back- well that is your coolant evaporating. A couple of minutes with the engine off is not enough to cool an engine; you probably run out of coolant thus no more steam. Did you check to see where the steam was coming from? I sugest you have the car towed to a garage to avoid further damage.
Spyros Papageorghiou

Can anyone give me an idea how long the procedure will take to do?
Dan Riley

The behaviour of the temp gauge rang a bell somewhere and I've just remebered what it was. Temp gauge went right up, turned key of, re-started, car ran happily for half an hour.

This happened a few times, getting worse each time (ie didn't run as long before getting too hot). Fully bled after each event.

Only time I've encountered that was a car which was sucking water into the cylinder across the fire ring. Not the fault of the gasket, more the corrosion in the head, looked more like electrolysis this one, etched very neatly. Had the right coolant as far as we could tell, but it certainly hadn't done the job.

The give-away was the foul-smelling exhaust, as the coolant when through the combustion chamer and out the tail pipe.

I have had erratic thermostats cause similar symptoms with the gauge, but taking a bit longer to drop back and without the smell from the tailpipe.

Like Brian we get the rear of the car as high as we can when bleeding too - makes it quite a bit easier.

Paul
Paul Walbran

Dan, depending on the speed you can remove the engine cover and identify the coolant bleed screws, about 15 minutes per bleed. Repeat at least twice (which usually takes about 5 minutes once all the covers etc have been removed.
Rob Bell

This thread was discussed between 16/08/2005 and 18/08/2005

MG MGF Technical index

This thread is from the archives. Join the live MG MGF Technical BBS now