Member
Hi
Having a problem with a M52TUB25 engine. This engine's block is essentially the same as a M54B25, if that helps. Engine has done 127,xxx km or 79,xxx miles. It has not done a lot of work.
Problem
- New to me car
- After changing the oil, there was a knock in the block until the rev's were lifted. This is how I first noticed it. Castrol Edge 5W-30 A3/B4 oil used.
- Very occasional knock when the engine is very hot, raise rev's and it goes away
- No oil light as yet. The oil light works correctly on start up, so its not a blown bulb or faulty pressure sensor.
- INPA rough running shows cylinder 6 always rougher than other cylinders. When hot, up to 3 times rougher e.g well off the scale. All other cylinder have very low rough running numbers.
- Developing bad leak at rear crank seal, its dripping.
Work to date
- Swapped coil pack to see if knock changed with the coil, it did not.
- Check spark plug to see if it was loose, no problem found
- Swapped plug with another cylinder, rough running stayed with cylinder 6.
- Preparing to pull the engine
Been doing some work on possible root causes to help speed up the repair. No use fitting new bearings if the root cause is not fixed. I suspect that one or more piston oil squirters have failed pressure valves (ball bearing held by a spring) and are dumping oil volume at low rev's when they should be turned off. This is starving No 6 con-rod bearing, No 7 main bearing and possibly No 6 main bearing. The worn bearing movement in No 7 main bearing being the cause of the rear crank seal leak.
Questions
- Has anyone had a similar experience?
- Does anyone have a picture or information on the oil ways in the block? I understand that the oil squirters are feed off the main bearings but have not found any information to confirm this.
- Any other suggestion on the cause of the problem or things to check.
Regards
Muzz
1999 2.8L Z3 Roadster,
2000 3.0L Z3 Roadster,
There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.
Member
I'd be more inclined to pull off the oil pan than to pull the engine out. Granted, the front xmbr must be dropped first, but I can get all that out of the way and open the bottom of the engine in about an hour.
I'm only familiar with the insides of the S-52 and S-54 engine architecture, so I'm unable to make any accurate comments about your engine, but it would certainly be possible to remove the #'s 5 & 6 rod caps, and the #6 main/thrust cap. The results of that inspection would reveal if there was a need to pull the #7 cap (for that, the xmsn, flywheel and rear main seal would probably have to come off__but I'm not positive without checking first, though I have some open engines here...).
For inspiration...
Aha! Proof that the #7 CAN BE removed in situ.
I was substituting polymer-coated main bearing shells for the standard ones prior to supercharging this S-52 engine.
Last edited by Randy Forbes; 11-16-2017 at 09:22 AM.
Literally a Cat
Do coated bearings exist for the M52TUB28? Uh, asking for a friend and totally not thinking any illogical or unwise thoughts about tinkering.
Member
The oil squirter orifice is tiny, even if it's stuck open it won't hurt anything. You only need a few PSI to float the bearing at such low RPM/load. I've had an engine where the builder left out the oil squirters entirely, making over 900hp and the bearings didn't suffer significantly - mains had some wiping and rods were like new. And if bearings start knocking then they won't get better with RPM, only worse (since there is greater load on the bearing at higher RPM) and they won't cause misfire until the rod goes out for some fresh air.
I'd guess your #6 lifter(s) are collapsed, leading to clatter and rough running.
Member
I make them exist by request,...Originally Posted by LannVouivre
S-54 connecting rod bearing
S-52 connecting rod bearing
They didn't exist for Austin-Healeys either, until I wanted them to.
TLML dry-film lubricant applied, before being cured
Oven loaded for curing process; part @ 300*F for one (1) hour.
Monitor process via thermocouple on coupon representing part density and weight.
To be continued...
Member
RandyF - what's been your track record on them... you've been doing them for several years: what have you seen? Wear mitigation, friction, heat etc etc... and any unexpected benefits? .. I'm in favor of coatings - just wondering what you've seen given the length of experience using them? .. likewise, if one is going to do a top to bottom rebuild of an M52/M54 motor: do you feel there's value in using them in such?... or is this really only for the S motors and FI applications?
Member
... continued from above.
If it slides/rotates, radiates or absorbs heat, then it's a candidate for dry-film lubricant, thermal dispersant or thermal barrier coatings.
So to answer your question...
... I have been doing this a bit longer than the pictures would indicate, since 1992 in fact__I have printed photographs of some of the earlier work. I haven't had the opportunity__or misfortune, depending on how you look at it__to have gone back inside of any of the BMW engines with polymer coating treatments, but I did see one (1) of my MGB engines after 80,000 miles of use.
In the case of the MGB, one (1) of the hardened exhaust seats dislodged, miraculously without any other damage, and it gave me the excuse to take a look see. While the dark color of the dry-film lubricant was rubbed "clear" in contact areas, at the molecular level, the impregnated graphite particles protected the surfaces to the extent that was hard to comprehend. If you subscribe to the theory that most engine wear occurs during startup, and if you've ever taken a used engine apart, assuming no real damage, then the piston skirts show the most wear, or scuffing. Sometimes the scuffing is borderline gouges__way more than just catching a fingernail__well the pistons out of the MGB engine looked brand new! The skirts were still black around the wrist pins, but the thrust surfaces were polished as pretty and smooth as if they were just newly cast/forged and ground.
All the bearings from the MGB were also in perfect condition. Once I got the cylinder head issue resolved, I reassembled the engine using all the same parts put back in their same position. Though I haven't seen that car since October 18th, 2000, the engine was still in service (as of several years ago, the car still sits in my ex-garage__verified with Google Street View).
They're terribly labor intensive to apply on an individual basis, and it's taken a long time to reach mainstream, but manufacturers are now supplying pistons__at least__on both original equipment and aftermarket levels. Performance enhancement may be negligible, but from an efficiency and longevity standpoint, I'm sold.
- - - Updated - - -
Anybody else using the browser Chrome and having trouble making posts? I have been, and it's been an issue for at least a few months, where I can't make the post__or sometimes even seeing the preview__from the "go advanced" tab.
I just lost (even after having copied it) a whole paragraph describing the benefits of the individual coatings on the cylinder head, but the forum blew it away (NOT THE FIRST TIME: )
Literally a Cat
I've had that happen a few times, it's pretty f'ing awful. I now usually select all and copy my whole post before I press the button.
Member
Thank you. Yes, I'd copied it this time too, but in the multiple attempts to post, toggling between the preview page and "site cannot be reached" (or some-such wording) screen it posted without that block of text. I thought I could edit the post, highlighting the whole post, text & links, then paste what I'd copied previously, but it just duplicated only what had already posted.
I was ready to throw my laptop into the pond (we live dangerously close to a small body of water...).
Strayed pretty far from a loose oil squirter on this thread...
Sim Simma
Moderator
Not to discount what those films do provide, I will say Ive taken apart a stock S52 that was starved of oil. Bearings showed virtually no wear. So little that had I not known it was starved Id consider reusing them. S52's didnt have the same rod bearing problems other (real) M engines have had. To me, short of building for 600+hp I dont see a point in putting treated bearings on an S52.
Post a thread in the forum software section at the bottom and they can help with those forum bugs.
Member
Look at my case. I was driving 20milla brake to cross and turned off did not want to turn on more seemed battery out of control. well the engine was very hard to turn with a wrench remove all spark plugs and run still a little hard turn turn testing oil change after loosen up chevere gave it a start like this and everything normal. when you plug the spark plugs and light it, it turns on by giving it, giving it about 30 seconds after giving it, it gets hard again. Bonda oil and fine probe has no oil canister and its oil was normal. The bathroom solenoids clean them. when it is hard I put everything down again I give it again and very slowly it comes loose. No fucking idea it can be. I watch the roar of cam and it's fine. It seems that a part is filled with oil and gradually blocks the engine.
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