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MG MGF Technical - MGF Underbody inspection

Well I bought an MGF, V reg, Nov 99 model, 25K miles. Yesterday I did a closer inspection with the car on a lift. The brakes all show more wear than I would expect, I have ordered new pads, but the discs may need replacing also. The rear pads, especially the inside pads are to the end. There are also square marks on the rear discs, almost like the hand brake over pressured the disc???? These are the originals discs and pads (I have the full service history).
Also there are signs of rust on the underside, especially the subframes and those big metal water pipes??? weird things, must be a better material than ferrous. Anyway I have a big tin of black hammerite paint, and I thought I might just paint all the rusty areas with it, unless anyone out there has a better suggestion. Do the water pipes fail from internal rusting, or external??? If it's internal the rust could cause some serious engine cooling problems. I have worked on many cars, but this is a different critter than I've seen before, any help would be appreciated
George Rainey

Not claiming to be a technical guru, but have read quite a lot of the posts on water pipes and brakes.

The water pipes do corrode on the F, and as there is a fairly strong perceived link between water loss and HGF, these really should be fixed. On a recent thread, there was a suggestion that these corroded from both inside and out, so beware of just hammeriting them. Replacement means bleeding the coolant system which is tricky. Dieter and others have lots of detail on their sites for DIY work of that type. Replacement pipes OEM are about 30-40 and Mike Satur does some coated aluminium ones.

For similar money to OEM, you could get EBC green stuff brakes and grooved discs. These appear to get better reports than the standard brakes, and the grooved discs will help reduce the dust build up. My pads were replaced long before 25k miles, but that might of been my early exuberance when I got the car. Although my discs are a lottle marked, they are still OK, and certainly no square marks.

If you look in the archives, there are lots of threads about brakes and cooling.

Welcome to the club

David Mills

Wait for the 36K miles service (when a coolant change is done) to replace the underbody waterpipes. And replace the clips with stainless Mike Satur ones.

I will not repeat what David has written as it is correct.

25k miles would be a good mileage for original pads and I suspect from the intimation of uneven wear between pads that these are originals. More spirited use of the cars perfromance will accelerate pad wear significantly and 12 to 15k miles would be more apparent for the fronts. Discs are now 'consumable' items and should be replaced when out of tolerance. (i.e. measured thickness, [originally 22mm], heavily scored surface, run out and other visible damage)

The cost of front discs is small as they are the same as vented Maestro/Montego and Metro GTi discs. The front pads are the same as Rover Metro in pattern, but anything other than front line names such as Lockheed, Ferrodo, Girling etc will perhaps not have the best friction materials. The rear disc is a one off and the rear pads are the same as a the Rover 800 models. THis indicates that cost of renewal can be quite reasonable and you will easily maintain quality, without buying from the dealers.

The inference of uneven pad wear and the 25k mile potential for the pads being original points a little towards the car not being used hard. Brakes are a fickle subject area, Be soft with brakes and show little wear on the pads and you often suffer from sticky pads that then drag and wear unevenly. Use the brakes more so that they wear pads and discs quickly and there is hardly even any incidence of stickiness and caliper siezure. This latter point is something that should be looked at with the rear brakes if the pads have indeed worn unevenly.

The pad marks on the discs is nothing to worry you as this is simply a feature of being parked for a period of time with the handbrake applied and little actual use since which will soon clean the disc off - unless the caliper is partially siezed. The clamping loads between the pad and discs will never ever be an issue and if there would be too much clamping force then what breaks first is the caliper casting, and this just doesn't happen.


Roger Parker


B&G at Baldock do an underbody clean and waxoil service.

They steam clean the underneath and inside the wheel arches and then spray a black waxoil type sealant over most of the underbody(except the engine etc.)and then a clear waxoil into the wheel arches.

I had my 5 year old F done the other week and it looks good and I hope it 'does good'.

They require the car for about 4 hours and their charge I thought was reasonable.

No doubt any decent garage could do the same.

Hope this helps

Tom Grayling


If you don't mind me asking, how much did B&G charge for this? Presumably 4 hours was elapsed time not labour.



Yes you're right, it was ealpsed time as I presume everything has to dry before application of the waxoil.

You will need to check with B&G but I think it was in the region of 150 pounds but as I intend to keep my car it seems good value.



Tom Grayling

Thanks Tom,

Mine'l be 4 yrs old next Feb - had it from new and like you I intend to keep it - which is why I was interested.


Well thanks to you all for your advice. I have already ordered "green stuff" pads for all wheels. I micrometered out the discs and found them all in tolerance so I'll re-use them.
The corrosion I mentioned is minor in nature, no exfoiliation or anything even close, just signs of problems to come. I still feel a good coat of hammerite in the problem areas will give the vehicle some more longevity. I work in electronics, maintaining RADAR systems, and navigational aids for aircraft use, I am a maintenance guy by nature, and prefer to prevent problems before they become major issues. I do enjoy driving her though.

Hi and welcome to the club :)

Hammerite is IMO the best stuff to protect visibly rusty subframes. Add wax after painting to the inner box profiles as well.
Due the water pipes. I think there should get no panic at newer cars like yours from 99. Coolant change after three years is IMO important and will hopefully supply the right balance of corrosion protection from the coolant mixture. Painting them from outside special at the weldlines is what I did and I hope to be sensitive enough and stop the car fast enough if anything blows and coolant goes off :).
I also changed most of the crap hose clamps to wider stainless steel clamps. Bought them from a metal parts shop. It wasn't easy to find all the required different dimensions.

MGF technical global search @ (brown box)


Whatever you do with the subframe/underbody make sure you coat with Waxoyl as a protective barrier!

Hammerite is good stuff - but being hard will chip and wear - grit etc

By using waxoyl you have belt and braces
This has a rust preventative in it
Also it "creeps" so if a section gets chipped /scratched the waxoyl will recover itself

Remember we are dealing with a car that "flexes"

Whatever you do - dont use the hard dry underseal
Two reasons

It splits as it ages and actually becomes a water/dirt trap

It is awful to remove and so very difficult to inspect the actual underbody

Yes Deiter,
I hate jubilee clamps too, I have already been researching better screw type hose clamps. Several of the water unions are showing weepage (not enough for concern yet).
Why they use jubilee instead of screw clamps I can't understand, there's little difference in price and they're so much easier to use.

they used this cause they are cheap and quick to install in the cars manufacturing process. Time is cash.
I found this clamps here in D for me useful.
Not complete from SS, but the sheet metal is 15mm wide and the screw changed to a SS material at the installed below the car for optimum rust protection. RH hose shows the difference. The smear is copper grease I applied to the non SS.
As mentioned already. The UK guys may look at MS kit. But I doubt that all the clamps from that kit need to get changed at once. Too expensive for continentals, though.

Tony, with you on the protection hints. But isn't 'Waxoil OVER Hammerite' better for the visible parts ?
Hammerite can be applied on thin rust. I'm no friend of chemical rust removal stuff. So I removed with a brush at good as possible, painted with hammerite and sprayed than when dry with wax.
This cause I think waxoil gets washed off always after a couple of month car use from rain and water on the road and needs each year inspection and re-spray.

PS. all around it's IMO better to do 'anything' than 'nothing' :)
Dieter Koennecke

"If it doesn't move, paint it", is a good philosophy. The hose clamps you are using are different to the type I usually use, but have the same result. Getting good quality SS, and some anti-freezing compound on the threads is always a good idea on anything you might want to remove later, especially I think those water pipe unions under the car. They seem so vunerable there, and if mine are weeping already, it's no wonder people are losing coolent and head gaskets.
All aluminium engines are prone to HGF, (remember the Hillman Imp)and without good cooling systems they will be more common. Aluminium has a high co-efficient of expansion, this would make it more succeptible to failure than any cast iron unit, especially with coolant related problems. Aluminium does have it's advantages though, especially weight.

I tend to crawl under my car alott - makes a good hiding place from the wife :)

Seriously - yes you need to recoat waxoyl about once a year but on the tiny underbody area of the F thats only a half hour job and will involve only parts that take the brunt of grit and water - you wont need to totally recoat just inspect and touch in!

This thread was discussed between 19/10/2001 and 21/10/2001

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