Do I HAVE to skim the head?

^ That is a little hardline.... it depends on if it is warped or not - the easy way is just to pull the head and check it. I would factor a skim into the cost from the start, but you might well be surprised that it doesn't need it.

Not all engines are the same so you just have to suck it and see by pulling the head.

What jasonb360 said. Check with a straight edge after you pulled it. That's the only way to tell. Everything else is reading tea leaves, so to say

In the past I had heads that needed a skim - and some that didn't.

Make sure you follow the untightening and tightening sequence as specified from the manufacturer! Should be in the workshop manual. If not, sent me a PM - I have one that covers the M103 straight six engine.

[edit] In the factory I think they bolted down all head studs together at the same time, similar as can be seen here. I've always suspected this has something to do with it... But don't know of course:



Cheers,
Jan

I'm also in the 'no' camp (unless you can get it done without having to wait long / spend much money)

Assuming the M103 is the same / similar head tolerances to a M104 the head bolts are VERY tight! Something like 50lbs then angle tightened 90deg twice (50lbs + 90deg + 90deg, leaving a bit of time in between) so unless it's warped to hell it 'should' pull down flat.. (not forgetting to do them in sequence)

J-69 - I bow to your superior knowledge of engines (mine is generally weak) but how do you check after a few hundred miles if they're not torqued down to an absolute value initially?

1) If an engine uses stretch bolts then re-torquing is unneccessary, and could even cause trouble by fatiguing the bolts. Most - not all, but most - engines that specify a certain angle of tightening will use stretch bolts. You shouldn't re use stretch bolts.

2) If an engine uses stretch bolts then the maximum head clamping force is determined by the platis yeild point of the bolts. No point going beyond it, and you might end up snapping the bolts.

3) You can only tell if it's going to need skimming when the head is off. Causes for skimming are either warping, normally due to significant overheating after being run without coolant, or corrosion on the sealing faces caused by coolant without antifreeze. If it's warped then you might get away with it, if the block has warped in the same direction. Unlikely though.

There's a chance that the HG (assuming that that is indeed the problem) has failed simply due to old age - gasket materials can rot. The HG in the previous engine in my Imp failed due to that.

personally chris for me it depends on the symptoms as to why your changing the HG.....loosing coolant,mixing,overheating,etc.....but if it were mine i'd get it skimmed due to the fact its getting on for 22/23 years old !!..while you're there mate bout time the grinder came out as i'm not feeling the wheelarch / tyre arguement ......lots of love the perm!!

Why on earth would you skim a head that's flat? That's just madness, a head that's warped beyond tolerance needs skimming one that's flat or within tolerance doesn’t, it's that simple..

Get the head off check it for flatness any decent straight edge will do, you do not need a £140 straight edge, it's nice to have one, I have a proper surface table and a straight edge for such jobs but you can get something perfectly decent for £30-40 that's well up to the job of a head, It' doesn’t have to be perfectly flat either most heads have a 3-4 though tolerance corner to corner, more for straight sixes or V10 or12's..

I've built hundreds of engines from full race screamers to old TD sloggers, and I've never skimmed a head that checked out flat and smooth..

Remember also if you skim the heads there are many other jobs that might need doing, such as shortening pushrods or rasing rocker shafts in hydraulic tappet OHV engines to skimming intakes to match on V8s..

Some manufacturers esp on diesels supply many different thickness head gaskets to compensate for how much has been skimmed off and keep the CR in spec...

Yeah, get the angle grinder out, 9 inch one should do it, skim it ya self. What could go wrong??? ;D

But yeah, check it's flat or get an old school engineering place to check it, they'd prob do it for a cup of tea and some rough shag (tobacco....) then just get it skimmed if it needs it.

Thanks for all the advice guys, it's all being taken on board. I think the plan will be to get it home and then strip it down myself (carefully, of course) and go from there. If it needs a skim, I'll get it done. Then my man can help me put it all back together.



It's still only an assumption that the HG has gone, it's not confirmed. The signs are all there though.

*dropping coolant level
*oil leak, though oil level doesn't seem to go down (presumably because the coolant is 'topping up' the oil)

That said, the oil is still clean as a whistle, no mayo on the cap or dipstick, either. And the coolant (when it was there) was oil free. Weird. It's NEVER overheated though, so I should be a step ahead of a full meltdown. Who knows. All I know is that I'm bloody sick of cars.

It's going into a specialist next week for a proper diagnosis (just to be sure) as that won't cost anything. If it is the HG (which I strongly suspect it is) I'll crack on with it.

Bloody cars.

Chris

EDIT: And yes, if it comes out of this ordeal in one piece I'll crack on and get it lowered.

Have a pic of a decent W126 for your troubles...

TBH i avoid modern stuff as often as possable ! but i do what comes in from regulars, mainly cab drivers who want a cheap job fitted inbetween the normal jobs whilst they are on holiday ect ;D
that 120K took him 14 months , it's still going as well

My old rover 420 leaked from the head externaly, when i took to the dealer they said Just whack another 90 deg on the head bolts nearest the leak that'll fix it needless to say i sold it and never owned a modern again ;D 8V iron heads for me from now on

Not sure where you are Chris but my local place don't charge for a straight test, it only takes 30 seconds to do so only costs the fuel to get there check waterways for corrosion that's more likely to be a problem if antifreeze hasn't been used and could account for the water loss ? as the waterway basicly becomes larger than the gasket reinforcement and i seeps out usually when the engine is off and the water pressure is higher than the cylinder pressure and you get a steamy ex on a cold start.