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MG MGF Technical - HGF Bolt length

Hi all

I've been having problems with my F ever since replacing the head gasket about 9 months ago, i was losing coolant more or less from day one and put it down to the thermostat housing, just recently the car started to overheat when in stationary traffic but was fine at high revs on the motorway, I then decided to sort it, and found that the coolant was coming out of the head near cylinders 3 and 4. At first i put it down to the previous head skim not being done right but after reading rob bell's website i measured the headbolts as instructed and found that the three front bolts near cylinders 3 and 4 were over a 100mm from block to cap, therefore they would never had torqued down correctly!!

I'm going to refit the cylinder head tomorrow after cutting and re-threading the bolts so fingers crossed.

I also found that the auto bleed valve was completely crudded up so i'm putting the overheating down to that?

If anybody else is having their HG replaced then I would check the bolts iaw robbs site.

"Cheers rob"
Wayne D

>I'm going to refit the cylinder head tomorrow after
>cutting and re-threading the bolts so fingers crossed.

please dont!

the bolts are 6GBP a piece and the thread is rolled (pressed in by rollers) , cutting a thread puts a huge gash in their structure and they are liable to shear.

If standard bolts don't finger tight to the right length then the oil rail needs replaceing, this can be done with the engine in-car, but you really ought to get your hands on a k-series manual (where you'll also find the recommendations on bolt stretch)
Will Munns

If the bolts are stretched then they have been over stressed and are on their way to failure.
Best practice is to always replace all the bolts, a budget rebuild may include reusing bolts that pass the length test but to rethread is asking for disaster.
Suggest that you follow Will's advice.
Geoff F.
Geoff Farthing

I suppose we have now got to the time when the *F* can be bought for very low sums and so we should expect to see many 'budget repairs' being undertaken.

BUT I agree do not try and save a few pounds on such items as stretch bolts - it will probably cost cost a lot more than the cost of these bolts if the head is damaged because of such a 'cost saving' exercise.
Ted Newman

I think maybe i left out the fact that i am fitting new bolts as i would not consider fitting the old ones,
Ref recutting the threads, what i am going to do is screw a nut on and remove 5mm from the end of the bolt, i will then clean up the end and take the bolt off hopefully making it so that the thread will grip.

Ted I am a professional aircraft engineer so i do know a little about materials and engines but even with the new bolts they are still bottoming out on the oil sump and ref "budget repairs", how many stories do we hear on this forum about "proper mechanics" in garages not even knowing how to bleed the car properly, i have previously had one looking behind the seats for the engine access panel!!!

Thanks for the comments though.

Wayne
Wayne D

Wayne, are you sure they are bottoming out? the reason I ask is that mine felt like that, but a new oil rail didn't have the problem - so the problem was deformed threads in the rail, not on the length of bolt.

you can't get upset with Ted for assuming the worse when you wrote "cutting and re-threading the bolts"
Will Munns

Hi Will

Maybe i am assuming they are bottoming out on the sump but i cant see how the threads would have become deformed as i am the only one that has removed and fitted the bolts since the car was new?
Is there any way of confirming this or is it a case of just replacing the oil rail? is it a straight forward job.
No offence Ted Will is right.
Wayne D

Wayne no offence taken - especially as I am ex RAF and have seen what professional aircraft engineers can do to an aero engine:-)

And as a BTW if the rail needs to be replaced I understand that a newer & stronger one was developed for the Land Rover K series engine - might be worth while following up on that route - I as an ex MT Fitter would certainly do that.
Ted Newman

the change in oil rail makes no diffrence to the head bolt torque (as I understand, stronger bolts were investigated and scrapped because they deformed the block)

Changing the oil rail can be done with the engine in place, it's an ar*e, and involves dropping the exhaust at the first join, after that the sump can be smuggled past everything else.

Although the head bolts hold the whole sandwitch together, there are assembly bolts which hold each layer (excepting the head) so you can remove the oil rail without it falling on your head!

you will need some GEC108 (IIRC) which is the special purpose sealent for the oil rail.
Will Munns

Ted, Professional Aircraft Engineers work with/to The Manual and Do Not cut 5mm off the end of an OEM bolt to make it fit.
I once walked into an Antipodean Air Force Hangar where the Base Commander showed me the Shadow Board with all their Tools for the Job. "Which Manual specifies the use of an Adjustable Wrench" I asked.
Next Visit, 4 Shadows were painted over !!
Geoff F.
Geoff Farthing

< "Which Manual specifies the use of an Adjustable Wrench" I asked.>

Haynes - came the quick reply!
Ted Newman

This thread was discussed between 24/07/2008 and 26/07/2008

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