Cylinder Head

[m.crawford]

Some of you might have read my poem (may have started something there!) about the HGF I suffered on Tuesday. The head is now off and gone to be skimmed but the guy said something about the head maybe being porous or cracked and needing replaced. I was just wondering how likely this is - as the cost is vastly increased if I need a new cylinder head?

I have always kept a close eye on coolant and oil and noticed no issues until one day after driving (carefully) for about 5 minutes the temp went up really high and the air blew cold. I stopped about 3 minutes later and switched off - all coolant gone! Does this sound like my cylinder head may have survived - or is it likely to be scrapped? I know it is probably a guess but at least someone on here will be able to make an educated one?

Anyway - I am pretty gutted about the whole thing and it means I will probably have to sell it (wife not happy about vast expense) and I am considering cycling for a while

Cheers

Martin

[Shug]

Porosity is something that can effect them, TBH. FWIW, Dave Andrews (K series guru) advocates peening the fire ring area before a skim, to lessen the chances of a skim uncovering any porosity (consolidates the material, removing any bubbles). It's not much to do with how the failure occurred, more to do with the original casting. Think aero bar - if you're unlucky.

[graeme]

Upsetting, but fixable.

If you sell the car and buy something else, what's to say you won't get a big bill from some fault on the new purchase?

Good luck!

[Shug]

Yeah - fair point - how much exactly are you being charged to fix a head gasket? Shouldn't really be much more than £500 - and you should really have AA P&L to cover it

[BiggestNizzy]

Why did the head need skimmed ?

[m.crawford]

I am guessing the head needs skimmed because it warped in the overheat? The price is considerably higher than that and includes; water pump, timing belt, spark plugs, oil, coolant, skimming, 12 hours labour and some other things I have forgotten.

MC

[BiggestNizzy]

I am guessing the head needs skimmed because it warped in the overheat?

Had it warped though ? everyone seems to keen to start skimming and whats wrong with the water pump ?

At this point I would like to state that I am an manufaturing engineer not a mechanic.

[m.crawford]

I too lack the mechanical knowledge to back this up at all. I tend to trust what I am told and put together bits and pieces of info in an attempt to make sense of it all. The car is with MMC who I went to as a result of the good feedback that had been on here for them recently (they fixed my suspension a couple of weeks ago and it was a pleasant experience). I do hope they are not taking advantage but I can never be sure.

MC

[robin]

There is chapter and verse out there on HGF causes, effects, how to avoid repeat occurrence, etc.

If you just send the head off to be skimmed, slap on a new gasket and move on, you'll be risking not only spending a lot of dosh but not being any futher towards fixing the problem.

The correct solution (IMHO) is:

Ensure liners are proud of the block by at least something, but preferably as much as 4 thou. If there is no protrusion you do not want to reassemble - instead you need to have the block "decked" to ensure that the liners are at correct height. This is expensive but necessary.

Ensure head is hardness tested with a rebound tester (not a ball-bearing type destructive test) in between the chambers and the exhaust side of the head face (this is, allegedly, where the head is likely to go soft). TBH, if the head has gone soft you're likely to be able to see indentations from the fire rings. But there are other causes of these, so you still need to test for hardness before wasting money on engineering costs for skimming, etc.

Ensure that head is peened before skimming, especially if head failure is due to porosity (you'll see this if you look at the head face with some idea of what your looking for).

Do not reassemble unless failure mode is understood. Otherwise it will fail again.

Do test for bolt stretch (as per the engine manual) and replace if bolts are out of spec, or just anyway if you're paranoid.

Use the MLS gasket & head shim unless your liners are wibbly wobbly in which case the OEM elastomer gasket is probably a tiny bit better at adapting to this. The OEM gasket has the down side that the elastomer can fail in due course without any particular reason; hence the MLS is better if all else is equal.

Use the steel head dowels; remove the plastic ones if fitted. All new gaskets come with steel dowels, but lazy fitters might decide not to bother using them if the plastic ones are in there already

Consider uprated oil rail if you have to have the block decked.

Consider PRT (Pressure Relief Thermostat).

These last two are more faith than science IMHO - but neither of them will hurt.

Cheers,
Robin

[m.crawford]

As a Lotus Specialist will MMC be likely to do al this? The guy did mention that this price included a number of tests on pressure and other stuff. If not - what am I paying for? Should I ask what the failure mode was?

MC

[BiggestNizzy]

I knew someone would put it all better then me, you should ask why it failed, ask what the liner heights are.

[hiscot]

Just to inform there is now a revised gasket kit from xpart this was devoloped for the N series and consists of
new single mls gasket
new 10.9 ( was 9.8 ) bolts to be used with a different torque setting
new ladder rail
only available as a kit ZUA000530
this was something rover was looking into before it went bust
there is also a new BW750 payen elastomer that has revised beading coloured blue

[robin]

Interesting on the 10.9 spec bolts - presumably higher torque setting?

Any idea what the rationale for that is? I'm assuming the single-piece MLS still has the shim, just that it's part of the gasket? With higher torque settings and no shims, you would think the tendency for the firerings to muller the head face would be much higher.

Cheers,
Robin

[robin]

MC, if you don't ask, you don't get.

Ask the detailed questions and expect a reasonable response. If you don't get answers or they fob you off, you'll need to think about getting the head tested yourself (it's an option, though would need sending away I think). If the block needs machining, they would remove it and you can organise the work to correct the block.

If you're uncomfortable with that, you may need to consider taking the whole thing elsewhere.

Cheers,
Robin

[m.crawford]

Thanks for the advice Robin - I will definitely ask if they know why it failed and if the liner heights are okay.

The quote I have at the moment is for everything rebuilt and includes the removal and skimming of the head, all labour and parts. The guy said that this would be the price unless the head is porous, in which case he quoted another 1-2 thousand pounds. Presumably this extra cost would solely be for the new head, as all the other work would remain the same, therefore if I was to source a head myself they would not charge any more than the current quote - does that make sense?

I have had a look on ebay and there are heads on there for the K series. Do you think that would be a good option if they come back with the news that I need a new head?

MC