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      06-25-2016, 12:22 AM   #1
Vanne
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Engine upgrade/refurb.. head gasket?

Late to the party, i know, but having just read this and also the M3 link that Byron posted up, ( http://www.m3forum.net/m3forum/showthread.php?t=547883 ) I am pretty darn glad i got new shrick dlc followers with my soon to be installed shrick cams.

These pics are pulled from that M3 thread… very disturbing…







All 3 pictures reproduced here without permission nor consent, for thread completeness.

EX2r and EX6r… holy crap!!! Langy was quoted as saying that from going through its protective coating to being flat like these would take only a mater of hours, the noise going from slight to loud.

wow, just very worrying indeed.. i wonder how my followers will look at 200K plus kilometres, with a bunch of track days thrown in.

Now about the Head gasket, is this something I should be looking at?? and if so, why?

Edit: I just got off the blower with my Indi, and the head gasket is a big job.. (he says) its not just the gasket, but if going that way will need, Head skimming, and valve grinding, but as the donk is already half apart, will save 1/2 the time on labour..

whats the consensus on this? Is a leak down test in order first? I have over 200k kilometres on my S54

No issues with the car at all, runs like a sewing machine, all preventive..

The other thing that worries me a little is the fact that i am not sure that dubai has a shop capable of skimming heads to the limits required, although my Indi assures that he has a shop thats very capable.

just gathering all the info before my car goes from the roller shop to my indies shop. for cams and vanos. so i have time..

would love some info here guys..
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      07-06-2016, 09:43 PM   #2
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"the M3 link that Byron"

..... Not seeing link
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      07-06-2016, 10:10 PM   #3
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Fixed, its a repost link from that /other/ forum across the pond. Its actually quite a good read.
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      07-07-2016, 07:09 AM   #4
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Thanks
I still surf through that forum on occasion but missed that topic.
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      07-07-2016, 01:44 PM   #5
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skimming a head is a very common practice on engines when replacing a head gasket, so there usually is an automotive specialized machine shop around to do that. How much there has to be skimmed is far more important.

But why does the head have to come off?
You have a blown head gasket? Oil useage?
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      07-07-2016, 03:08 PM   #6
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Bedankt for popping in Guidok,

There are zero issues with my car aside from being high milage. no oil usage (don't drive enough to notice anyway), but thought due to the milage it may be a good idea to have at least a leak down test while i have to top of the engine apart anyways..
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      07-07-2016, 03:17 PM   #7
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Yes a leakdown test never hurts. Although leaks can go up (valves/stemseals) down (rings) or sideways (gasket). but its a first pointer to look for faults non destructively

But regarding removing the head: if it aint broke..
Removing the head is never without risk. Now it fits snug, but under tension. Remove it and the tension might result in warp requiring a skim. And refitting a different head gasket might not have such a long life, aluminium head on steel block is always difficult.
This current gasket/dir obviously is a good one looking at the miles.
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      07-07-2016, 03:29 PM   #8
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Thanks G,

any idea of the sort of numbers i should be looking for in the leak down test (never have done one before) whats good and whats bad?
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      07-07-2016, 04:51 PM   #9
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Leakdown readings are not actual readings. More like a percentage.
I think you have 2 meters on the tester. On the leakdown apparatus you connect a shop air hose (dont know how many pressure exactly), but the first meter shows the input shop air pressure which you regulate with a pressure regulator to the desired pressure (I think there is a green and red zone on the meter), and after that input meter the air goes through a very small valve (so you have very little airflow to the cylinder) into the cylinder. That air pressure (in the cylinder) is also measured. If the cylinder leaks more air than that very small valve lets through, you get a big pressure drop. The percentage difference shows if its good or not. But I think on both meters it shows what a good zone is and a bad zone (where the needle points too), as the design also depends on the size of that small valve.

But you should do both a compression check and a leakdown check. A compression check can also show problems in timing and local problems on a cylinder wall. With the compression test the engine rotates and with the leakdown test it doesnt (so it only tells something about the engine in that position). So the leakdown test is a bit different. that is really useful to physically locate the problem if you have a problem. But to determine if you have problems, also do the compression test.
You should do the compression test at least with a hot engine: it's most important that the valves close when the engine is hot, thats when the valve stems are longest so if valves dont close properly (worn valve seats, valves out of adjustment), it shows on a hot engine, not a cold one (on a cold engine there is room on the valve adjustment side, so there is always room for the valvespring to push and close the valve).

For a leakdown test I'm not sure what's better hot or cold (or both).
A good mechanic will know though (I hope...)
I'm not sure how accurate leakdown results are and if they are easily interpreted.
The compression test is much simpeler and fairly straightforeward (if you use the proper procedure)... Either you loose compression or you dont. Leakdown can point out where you're loosing compression.
I also wonder that when you dont loose compression on a warm engine a leakdown test is still necessary or that it can still tell you something.

For the compression test: if you have a very healthy engine, the hot compression test will be slightly higher than the cold one (piston rings are slightly longer so the gap is shorter although the block expands too), but if you have a problem in the valve train the hot compression will be lower (and it will show in 1 or more cylinders that might not show that on the cold compression)
So always do the hot compression test, you primarily want to know how the engine performs when its hot.
Wear gloves/protection when working on a hot engine.
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Last edited by GuidoK; 07-07-2016 at 05:18 PM..
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      07-07-2016, 05:07 PM   #10
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I would do both hot and cold ideally if possible. And you're looking for a leak-down number with less than 10% deviation ideally, it can be higher and still run well enough though. Consistency cylinder to cylinder is perhaps even more telling than the individual values per hole because if they are consistent it implies even wear over time rather than an issue generally speaking.

And yes as mentioned above it is literally comparing input pressure to the output pressure to note the difference. If it's 100 psi in and you see 95 psi out than you are seeing 5% leak-down.
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      07-08-2016, 03:36 AM   #11
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Thanks guys, some really good info there. Ill need to have a sitdown with my indi and have a good chat. Will do compression and leakdown test.
Ill post up the results. Hopefully as Guidok said, if it aint broke, don't fix it,
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Last edited by Vanne; 07-08-2016 at 07:59 PM..
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