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MG MGF Technical - HGF - not sure!!

Hi,

My F has been off the road now for a couple of months with what I thought was a HGF. However after looking at a few websites I am not so sure. The symptons are as follows:

1. The car over heats when I am in slow moving traffic if you open up the inspection lid steam and water are spitting out of the water tank, on the open road it runs fine.
2. The dipstick has some mayo like stuff on it mainly towards the top of the dipstick, however as I have read this could just be condensation
3. I have removed the oil cap and this is perfectly clean.
4. When the car was on the road it was going through a lot of water and at no point was it green as some websites have stated.

Any help would be greatly apprciated as I have just been quoted £1471 for HGF repair...and I really can't afford that.

Many thanks
Drew
A Hyatt

I am going to make the assumption that the quantity of mayo on the dipstick is pretty small (this would fit with condensation).

The slow speed over heating and consequent release of steam could well be down to a combination of two factors:
1. non operation of the radiator fan (either due to the common problem of the ECU water temperature sensor failure - or due to blowing of the radiator fan motor fuse - more here: http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/related_problems_overheating.htm)
2. Failure of the expansion tank pressure cap.

See link above on diagnosing a problem with the radiator fan - and replace parts as necessary (about 10 quid tops), and replace the expansion tank cap as a matter of course (about6 quid from Halfrauds)

The loss of water on journeys may be harder to explain - but if there is a large about of residue around the pressure cap from evaporated coolant, then I think that this may point to the answer.

HOWEVER

if you find that the rate of coolant loss is greater the harder you use the car, then I would not only fear a head gasket failure, but I would be looking out for a new (or second hand) cylinder head... :o(

Fingers crossed, and do let us know what you find!
Rob Bell

Thanks for the advice Rob.

I have just checked fuse #6 as it states on the link you sent and it is indeed blown. I will change this tomorrow.

Should I be topping up the expansion tank with just water or should I be adding something else to the solution?

I just hope that when I was driving it with this problem it hasn't caused any more damage.

Thanks again.
Andrew
A Hyatt

No problem Andrew - some recommend substituting the 10 amp fuse for a 15 amp one - as used in later versions of the MGF and TF. The problem can be that the fan sticks after a period of inactivity, leading to the motor taking a larger current draw and blowing the fuse... Might be worth considering on your car if this happens again.

Topping up the coolant tank, yes you can use just water - the amount you'll be adding will be modest compared to the total volume of the cooling circuit, so any dilution of antifreeze will be minimal.

Definitely replace the pressure cap though - there is a good chance it'll be cream-crackered now after a few over-pressurisations/ overheats!

Let us know how things get on :o)
Rob Bell

Hi,

I have replaced the fuse as recommended but not the pressure cap - halfrauds where out of stock.

I have just started her up for the 1st time 5 months and she ticked over quite nicely considering, although there was a quite a bit of smoke/fumes blowing out of the back - is this to be expected?

Also, what is the best way to test if the radiator fan will now work. I can't take it out as the tax and MOT have expired..!!

How much am I looking at for replacing the cylinder head inc labour?

God I hope this is all worth it...

Thanks
Andrew
A Hyatt

Andrew, if you leave the car to idle, the rad fan should kick in after about 30-45 minutes. Either that, or the temperature gauge will head north...

A straightforward gasket swap is not too difficult. Can't remember the parts prices, but an eBay shop should get a gasket set, set of new long bolts and all other sundries for about 100 quid, but say, a couple of hours labour.
Rob Bell

Thanks again Rob.

Talking about my temperature gauge, I think I also have a problem with that. When the "F" used to overheat the temperature gauge never went over the half way mark, infact it hovers around that mark most of the time.

When I have spoken to people about HG changes they said it needs to be sent of to be re-skimmed or something, is it not cheaper to just buy a new one?

God I wish I found this site 8 months ago...
A Hyatt

A skim doesn't cost that much - the risk in going down this route is that the head will still be unusable having invested that cash... The head casting can have small cavities - or porosities - under the working surface that can be exposed by skimming. Broadly speaking, if these porosities are away from the fire ring, there isn't a problem. If it is - then gas can bleed past the fire ring and pressurise the coolant = HGF.

A head in this condition could be saved using a shim - or indeed using the new multi-layer Landrover gasket set.

If the head has gone too soft, then no amount of skimming will help - the material will have lost its quench and therefore crystal structure... If there are very deep fire ring depressions in the cylinder head, then I am sorry to say that it is scrap. See pictures of my old cylinder head... http://www.mgf.ultimatemg.com/group1/info/journal/blog/index.htm

All this may tempt you to get a new cylinder head. I wouldn't rush off and buy one just yet - if you are removing the cylinder head, inspect it. Slight circular grooves are okay and can be skimmed out. And this would be the first thing that I'd do in your situation.

Failing that, get a new cylinder head. And if you are into tuning cars, then there are a number of interesting castings you can lay your hands on that'll help you liberate a few extra Gee-Gees as a silver lining to that dark HGF steam cloud...
Rob Bell

Hi Rob, me again...!!

Ok, I have changed the fuse and I have just left the car running for the last 35ish minutes. The temperature gauge was just under the half way point. At this point the fan kicked through the airflow chamber on the back just behind the drivers door.

When I turned off the car I could easily hear the water bubbling in the expansion tank and I could also hear water bubbling from somewhere around the engine. Not sure if this is correct as I am sure if the water is bubbling in the tank it must also be bubbling around the pipes etc.

I have inspected the tank cap and that is indeed b*ggered, the rivot in the middle is off centre. So I will try CAF for a new one.

Do you think I will still need to replace the ECU water temperature sensor?

Cheers
Andrew
A Hyatt

Did the radiator fan (at the front) kick in? The fan at the back just pushes a bit of air through the engine compartment,it's the rad fan that really needs to come on.....I think.
Pete C

Yep, the radiator fan is barely audible compared to the engine bay fan. Check the fuse again for the radiator fan, you may find it has blown again, which suggests the fan motor has failed. If the fuse is intact, run the engine again and keep your ear close to the radiator and see if the fan is spinning up or not.
Mike Hankin

I am pretty sure there was no noise coming from the front radiator fan. I have just checked the fuse and it is still OK.
A Hyatt

You literally have to stand in front of the radiator to hear the radiator fan kick in. The side intake fan is far louder...

I'd suggest a re-test :o)

The bubbling noise could just as easily be from air trapped in the cooling system from previous over heats. If you can gain access to an exhaust gas analyser, you can check for the presence of hydrocarbons in the expansion tank; their presence indicates HGF.
Rob Bell

Whilst you're grovelling around in front of the car with ears tuned, have a look through the grilles at the condition of the radiator; if a significant proportion of the cooling fins have corroded away the cooling capacity is seriously reduced, and this may be contributing to the problem. My money's still on a failed radiator fan though, but whether the gasket has conked out as a result would only be clear after the 'sniffer' test Rob suggests.

Rob, are you still getting better mpg with the 135 head? If so, that's a definite silver lining to needing a new head 8-)
Mike Hankin

I've honestly not made a formal assessement of the fuel consumption Mike - it's probably about the same as the original head and cams - which given a comfortable 20bhp gain in power, is no mean feat! :o)
Rob Bell

OK, I have completed a re-test...

The result is, after around 35 minutes of idle running the expansion tanks starts to bubble up to the top. At this point the temp gauge is at the half way point.

At no point did the radiator fan come on, by turning the wheels to full lock left I could just about make out the Radiator fan (yellow) and there was no movement.

Also, the side intake fan didn't start either.

A Hyatt

Is replacing the radiator fan mator a simple job?

I had a brief look last night and it looks like the whole front needs to come off...any advice greatly appreciated.

Cheers
Andrew
A Hyatt

Have a look at this site:
http://www.mgf.ultimatemg.com/

Go to the technical tips area and it shows you how to test the fan.It may be easier to do this first to make sure it's actually faulty....

Pete C

Andrew, as Pete suggests, we still don't know whether the fan works, but if you say that the coolant appears to have started boiling, then we know that the pressure cap needs replacing, as it is failing to maintain the coolant pressure (if you remove the cap, is there any pressure release when the coolant is still warm - be extremely careful doing this for obvious reasons - I use an old large bathroom towel)

The other way to test the fan, as indicated by Pete and on this webpage http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/related_problems_overheating.htm is to disconnect the ECU water temperature sensor while the engine is running. The plug has a retaining clip that is released by pressing down on it and the plug can then be withdrawn from the sensor.

Irrespective of whether the engine is hot or cold, the engine management will assume that the sensor has failed and go into 'fail-safe' mode, and run the radiator fan...

This is what I'd do next to ensure that the fan is operational :o)
Rob Bell

Thanks for everyone's comments, it's such a great help to MGF novices like myself.

In fact my wife nearly passed out when she saw me laying on the ground trying the locate the radiator fan, and my son thought I was looking for one of his footballs.

Before this thread the most techincal thing I had done is to put petrol in.

I have planned sometime this weekend to locate the ECU and perform the tests that have been stated above.

First things first I need to get access to engine...that sounds like a task in it self...:¬)

Are you guys have been fantastic.

Andrew
A Hyatt

No worries Andrew :o) You'll make us blush!

Getting to the engine cover is pretty straight forward, but I'd recommend getting a ratchet spanner (10mm) for the screws under the T-bar trim... http://www.mgf.ultimatemg.com/group2/DIY/maintenance/engine_access/engine_cover.htm

Good luck! :o)
Rob Bell

I've just paid c£1100 for a HG repair, after local garage diagnosed HG failure. Whilst there was no sign of any water loss or any getting into the engine, I had steam and bubbling from the filler cap after a relatively short journey. I've ordered a new one, just in case the present one is faulty. The garage skimmed the head and replaced the cam belt, water pump (signs of leakage on the old one), front to back radiator pipes (old ones also showing dampness around the welded brackets)plus the usual bits and bobs. I'm hoping it will be OK and I'm running it down to Exeter and back tomorrow to find out! There doesn't seem to be any such thing as a cheap repair, especially if you want a proper job done.
D Gray

Right...

I have performed the following checks...

1. Removed Engine access cover..good start
2. Located ECU and removed connection
3. Started engine and sure enought the radiator fan started immediatly.

However, I was unable to remove the ECU to clean the connections - does anyone have any tips on this.

Also, whilst I had the engine access cover off I had a good look around for HGF signs.

1. I removed the oil cap, there was no mayo stuff on the cap.
2. I noticed on the head cover and down the side of the head unit on right hand side (towards the front of the car)a fair amount of oily stuff (I know it a terrible word) but the other side looked quite clean - any ideas?

Thanks
Andrew
A Hyatt

This thread was discussed between 23/03/2007 and 30/03/2007

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