Winding noise from rebuilt engine?? - The Unofficial BMW M5 Messageboard (m5board.com)

Fordkoppie · 13th October 2009, 22:37

Hi everyone,
I am from south africa and I really wished that my first post didnt have to be a technical question, but since i am completely new to ///M ownership, i really didnt have much to yak about.
I dont have any pictures of it yet but it can be seen on the M registry BMW M Registry - Car Detail in some terrible resolution pics
I have had plenty of e30 325i that i fixed and sold for a better one every time ever since i started driving and i am completely smitten with these legends but this is now my first M and i must say that ownership has been nothing but pain so far.
I bought my 91 diamond black 3.6 e34 M5 in May 2009 and only had it for 2 weeks when i realized that this car is no way near what it was supposed to be. The previous idiot really gave me a raw deal since he said that the motor only had 20000km on it since a comlete rebuilt including a new sub assy. Turns out the bottom end was new but the head was in terrible condition.
To cut a long story short everything that seemed like it had the sligtest indication of wear was replaced and a set of new stainless steel big valves (2mm bigger than std because of the worn seats) were installed.
i did a forum search and saw that everybody reccomended fitting a S50 b32 timing chain tensioner. i did not replace the chain or guides since i could see that they really only had 20 k on them and looked perfect.
After the rebuilt that took 4 months to complete the engine was fired up just a few hours ago and everything seems perfect except that i noticed this whinding sound coming from the front of the engine. Like i said, i only drove the car for 2 weeks before dismantling it and cant remember if the noise from the chain was the same or if it is now louder. It defenitely had the same type of noise but am not sure if the loudness was the same. It has been a very long time since i have heard any other s38 running, so if you experts can please tell me if it is normal for the timing chain to whind or should it be completely silent?
I do have to add that the previous idiots skimmed the head and the end result was that it is now 0.8mm thinner than standard and the cambox has also been skimmed by 0.1mm = 0.9mm total.
Seeing that the cams were now closer to the crank i fitted vernier cam sprockets, cut bigger relieves/"eyebrows" in the pistons for the bigger valves to clear and also put a 4mm spacer behind the whole double acting piston of the S50 tensioner to take up the extra slack of the chain due to the skimming. The combustion chamber has been polished to get the cc's right to achieve the std 10:1 compression ratio.
in the end it worked out to be 10.3:1 but that wont matter since where i live is 1300m above sea level, so pinging wont be an issue.
I really love these cars and hopefully i will be able to enjoy it now when everything is fixed.
Your advice would be greatly appreciated.
Thanks,
Chris

1day · 14th October 2009, 01:45

welcome

you've gone way past my abilities to help, you certainly no more about mechanical engineering than I do reading your post!

However, I can help in another way by suggesting you post a video of the engine running, any mobile phone video should suffice as it's the sound your after so picture quality doesn't really matter.

You can attach the video to your post on here as an attachment, or a link to a you tube video?

that way the experts on here can have a listen.

My car is from SA originally, it's 3.6 1991 (april) in ice white with silver grey extended nappa.

Hope it goes ok for you soon.

(btw I remember reading another horror story from a newbie owner from SA on here, also involving head problems... could well be unrelated / pure co-incidence, I can't remember much more about it to be honest)

Sub8 · 14th October 2009, 15:10

Have you tried running without the FEAD belts to check these as a possible source of the noise?

Ratty · 14th October 2009, 17:35

I recall from a thread on here somewhere, that there is a specific fitting procedure for the e36 chain tensioner.
I can't remember exactly, but if not done correctly, it fails to tension the chain, and I think that might lead to a 'winding' noise.
One of the guys on here had a problem and one of the esteemed experts did a nice write up for him.
I had mine replaced by Faz and it's almost silent.

Raymondw's excellent write up:

S50B32 chain tensioner upgrade for the S38B36 and S38B38

Also you have to be careful to remove any water/moisture from the blind bolt holes or it can lead to block splitting as it boils.

Tomba · 14th October 2009, 19:46

How long have you runned the engine after rebuilt? More than 2 minutes? Otherwise you could implement the sound of the secundairy airpump as whining. Loose the belts like Sub 8 discribed and if you don't hear the whining it might be the airpump...

Hope you have more luck with the car, I'm on 2nd rebuilt... (3rd engine).

Fordkoppie · 15th October 2009, 10:59

Thanks for all the input,
The best way for me to describe it, is that it makes the same type of sound as a supercharger but not as loud as the SC
I listened with a doctor's stetoscope on the engine while it was running and it definitely came from the timing chain.
To make sure of this i even took off all the external belts and started it up for +- 10 seconds = same noise.
Ratty - Thanks for that because i only wanted to know if it can be quiet or if all of them are noisy.
I made that there was nothing in those blind holes, because i have read Jrobo's article on the split block.
Tomba - In south africa we didnt have any emission controls in '91 and therefore the airpump is not connected nor does it have any pipes coming to and from the pump. No cats also. The airpump is only there to act as a very heavy idler pully to keep the belt stiff.
I am going to take out the 4mm spacer in the back of the tensioner today and see if it is quiet, because the more i think about it, the more i think the cain is too stiff. I drove it for like 6km so i hope it didnt damage anything in this short distance.
If i may ask(Tomba) - why are you on your 3rd engine and what is the total mileage of your car? In what manner do you drive it?
Regards

mottati · 15th October 2009, 19:38

Quote:

Originally Posted by Fordkoppie

I am going to take out the 4mm spacer in the back of the tensioner today and see if it is quiet, because the more i think about it, the more i think the cain is too stiff.

? spacer, i don't remember a spacer. The chain tension is pretty important. If you think the tensioner you have is causing an issue, i'd try to find an oe s38 tensioner to see if the noise goes away.

Tomba · 15th October 2009, 20:05

Quote:

Originally Posted by Fordkoppie

If i may ask(Tomba) - why are you on your 3rd engine and what is the total mileage of your car? In what manner do you drive it?
Regards

Cars was bought with an engine with damaged conrod bearing and crank. During rebuilt someone should bring the bearing caps to the company were they balanced the crank. To make a long story short, they never ended up there. According to Mr.X it wasn't necessary to replace the oil pump because they never fail (not!). @ 240km/h another bearing was damaged. Then we were about to buy a other engine with car @ Hollanders. He said the engine was completly rebuilded with new pistons etc... after 3k km conrod bearing were flying around, valve clearance was out of spec. During disassembly I saw that non-S38 conrods were used (they don't have the possibility to remove weight from the small and big end, but these were) After removing the head which was sealed of with to much liquid gasket I saw non-S38 pistons. So that leaves me now to engine #3. For those around a warning, avoid this man/company Hollanders. The pictures may speak for them selves....

day · 15th October 2009, 21:35

My feeling is that for some reason the substitute tensioner is over tensioning the timing chain. If a chain is too tight it will whine (and eventually snap). I replaced the tensioner on my 3.8 with the later one and on start up noticed a whine that wasn't there before - I decided to replace the tensioner with a new original one - problem solved. I admit that it is possible that I'd fitted the replacement tensioner incorrectly (but I don't believe so) and can only think that the later part just wasn't compatable.

inertia8 · 16th October 2009, 05:48

1day, I thought that some whining/singing was meant to be expected from the tensioner upgrade as it does keep a slightly higher tension on the chain? Perhaps not to the degree experienced by Fordkoppie.

Fordkoppie, Jrobbo on this forum had to have his head decked to return it to flat. A company here in australia made up a "shim" to replace the thickness of the head material that was machined off.

IIRC his cas done over 100,000k's on this setup. John might be able to correct me.