replacement piston and rings help

[xSamuraix]

Hi....

In short, my engine is a bit screwed. Low compression in only 1 cylinder, 121 dry and 162 wet in the compression test I did.

Is it as simple as removing the engine, stripping it down and just replacing the piston and rings and getting a rehone (just to be safe) and replacing both head gaskets?

Once I do that, how would I time it again?


97 540i pre vanos

[StRaNgEdAyS]

What are the compression figures for the engine?
Honing these engine blocks is a special procedure using a special paste and hone to treat the cylinder walls.
It's also uncommon for the bores to require such treatment unless a ring has had a catastrophic failure.
What was the history leading up to testing the compression in the first place?

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[philly98540]

If the cylinder walls are perfect, your OK. Don't hone them. If there is cylinder damage, its ups the ante big time. The cylinder needs a special treatment after machining to expose the special wear surface. Then you need oversize pistons. Cheaper to source a used engine.

You can google alusil cylinder honing to find more.

If the cylinders are in fine shape, new rings can be put in with good results, but I've never done it on these engines. You can search and find stuff to help you.

- - - Updated - - -

Strange beat me by a minute. LOL.

[xSamuraix]

Strangedays, Can't remember the compression test results now, but they were roughly all 162 - 175 dry.

What happened was I got stuck in a ditch, over revved and the splitter under the bumper came off, hit the viscous fan knocking off 5 blades then 1 or more shot through the radiator. After that I had a stronger smelling exhaust fume coming out and much more of this smoke in general coming out. Then, the acceleration after I got out the ditch was really bad as I lost all the coolant, thankfully it was only a 2 min drive to get home limping.

[StRaNgEdAyS]

It's unlikely you'll l need a rehone.
I hazard a guess judging by what happened, you'll probably be fine with new head gaskets and have your heads checked and reconditioned. Still a big job on the scheme of things on these cars, so I'd also get timing chain guides and tensioners done while to you're at it, but I would suspect your bores are fine.

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[777300ER]

If it started to get sluggish that means you overheated the motor to the point it was about to seize... That motor is junk.

[xSamuraix]

777, with no water cooling and no coolant it would have acted like that I thought? Acceleration being poor.

Got to figure how to get the engine out yet, hardly no level ground here.

[geargrinder]

In short, my engine is a bit screwed. Low compression in only 1 cylinder, 121 dry and 162 wet in the compression test I did.

Honestly that's not that bad. Spec is 174-203, max delta 7psi between cylinders. Given its that minor, seems likely it'll just be the head gasket. Other guys are right about the rings and honing (i.e. don't hone unless you find something majorly wrong, which you won't...) This should be a HG job not a rebuild. OF course famous last words but you'll know when you get the heads off.

Most fun part of this will just be dealing with the exhaust manifolds off. Another thread was just discussing this recently.

[xSamuraix]

Gear, what thread is that? I really am a engine newbie, been watching loads of videos on youtube about this also.

[xSamuraix]

I found the actual compression test results..... Dry test.

8th cylinder =179 4th cylinder = 180
7th cylinder = 185 3rd cylinder - 172
6th cylinder = 123 2nd cylinder = 174
5th cylinder = 184 1st cylinder = 175

[geargrinder]

I found the actual compression test results..... Dry test.

8th cylinder =179 4th cylinder = 180
7th cylinder = 185 3rd cylinder - 172
6th cylinder = 123 2nd cylinder = 174
5th cylinder = 184 1st cylinder = 175

Yeah. Sumfin wrong for sure. Even though its technically "out of spec" personally I'd consider the 172-185 range to be totally fine for old gals like this. But the 123... mmm... yeah more worrisome.

Gear, what thread is that? I really am a engine newbie, been watching loads of videos on youtube about this also.

Sorry. Never replied to that. It's this. Ironically he wasn't the slightest near needing to pull a head... but there was discussion of considerations and options in there before we realized he was jumping to comcluzunz.

https://www.bimmerforums.com/forum/s...-E39-M62-motor

[xSamuraix]

I'll pull the head off that side and see what is going on, least retiming it wont be that bad as no vanos in this engine. However, when I look at these timing blocks that go over the cams at the end, will a cheap set just work ok? Also, which this kit attached to both of the cams each side of the engine, can I pull the heads off with this kit attached? I'd mark the chains also to make sure they are all lined up after reassembly.

Thanks for the link also.

[geargrinder]

yeah the problem is the cam sprockets are semi-infinitely adjustable on these motors. with the NV motor I think they are bolts-in-slots at least so its not totally 'infinite' but you get my meaning - it's not "off by a tooth or NOT" like a motor with a splined or keyed cam. the marking COULD work but you'd critically need to mark sprocket to cam position. I can't say first hand on the cheap copies but guys have certainly used those before succesfully...