Author Topic: Extended tensioner slides in w/o force??? (Read 14436 times)

PeabnutBubber · « **on:** October 28, 2011, 01:39:37 PM »

Hey there, this is my first question here and I didn't see this topic covered yet.

I turned on my engine the other day and suddenly I get a terribly loud noise/rattle upon start-up. I diagnosed it myself after doing as much research as I could as the timing chain rattling around like crazy. It had that diesel-ish sound alongside a hardcore rattle.

After ordering a brand new tensioner, I pulled a chain tensioner from a fresh m42 at a junkyard just to see. After taking out the old one in my current m42, I went to replace it expecting it to be difficult to push in (apparently it takes around 20lbs of pressure?) but to my surprise the whole piece slid in and I tightened the 19mm cover with no resistance whatsoever. The junkyard tensioner had plenty of resistance on the spring. Even the old tensioner has significant spring tension still.
(http://www.m42club.com/forums/showthread.php?t=2925)

After cranking the engine, it ran rough and then bogged out and shut itself off. On the second crank, it ran fine and began to sound better than before but still the rattling was very present and pretty loud.

Sorry about the novel but it leaves me with these two questions;
1) Should I try the new tensioner and not return it ($50) and
2) Does this look like I'm going to have to dive into the timing case to fix something important in there or what do you think?

Any knowledge will help of course as well. Thanks a ton!!
Luckily I can bike to class every day but I miss driving the ladies around. :cool:

DesktopDave · « **Reply #1 on:** October 28, 2011, 04:06:22 PM »

I'd be worried that the idler gear bearing has gone away. That'd put a lot of slack in the chain and prevent the tensioner from, um, tensioning anything. Did you pull the cam cover to see if the chain and cam gears are OK?

It's happened several times I can recall on this site. That was changed mid-production to a deflection rail. I don't think you can see that from the upper case, but I haven't done it myself yet so I'm not totally sure.

PeabnutBubber · « **Reply #2 on:** October 29, 2011, 12:28:40 AM »

Thanks for the reply Dave, I'm going to have to do a bit more reading about the timing case and everything going on inside it, for sure. I haven't opened it up yet but after I look it up that will probably be my next step. I'm guessing since the bad-sound happened so abruptly it was more like something broke than something wore out (like the tensioner), but that's just my best guess.

DesktopDave · « **Reply #3 on:** October 29, 2011, 07:50:40 AM »

In this RealOEM diagram it's part #11 that tends to fail. The internal bearing cracks and what remains just clatters away. There are also isolated cases of the guide rails, bolts or even the timing chain case failing.

The toughest part of pulling that front case is the main pulley & bolt. Specification is 240 ft-lb or something crazy like that. If you get a breaker bar on it you can tension the bar then bump the starter to start the bolt loose.

You don't have to tear apart the front case yet. Drain the oil through a strainer & maybe even drop the lower oil pan to check for debris. If there isn't anything in there, it might be that the chain skipped a cam tooth or two instead. In that case, I'd guess one or more bent valves. A compression test would quickly verify that.

Good thing you have a fresh M42 in a salvage yard nearby. The later cases swap directly on the early block, it's a desirable upgrade. I'm told that even the later e36 serpentine belt setup can swap over...I was considering that myself to get the updated a/c compressor for an r134 conversion. Most of us would need to find a shorter belt though...due to our P/S delete.

I'm keeping my fingers crossed that it's the idler gear or a guide rail. You have the impossible luxury of working on the car all year 'round too...could be worse...the car could be broken down while it's snowing. You know, like it is up here right now.

PeabnutBubber · « **Reply #4 on:** November 01, 2011, 10:51:13 AM »

The weather really is perfect here right now- 60's and low 70's. Again, I can't thank you enough for the opinion. So, I think my next step will be to do exactly what you say and pull down the oil pan and check for stuff that shouldn't be in there. I'm hoping it really is just a rail or that pulley. That diagram makes everything make sense as well btw. If it is a case of valves, then I may just look into dropping in another m42, although I have not done enough research on the plausibility of that... Or on the replacement of valves or related damage for that matter.

I hope I'm not in over my head here, but hey, I don't mind learning how to take care of this thing. The more I work on it, the more of an emotional connection I'm starting to feel. haha

I'll keep updating on what's going on and provide pictures if I can as I take it apart. Hopefully more people will input some knowledge as well. Anything helps, I'm kind of a noob at all this and I find these forums/google to be invaluable to a DIYer like myself.

PeabnutBubber · « **Reply #5 on:** November 04, 2011, 08:50:18 AM »

The weather really is perfect here right now- 60's and low 70's. That diagram helped everything make sense as well and thanks a ton for the opinion and the knowledge.

I took your advice and dropped the oil pan to see what could be seen. There were no particularly large chunks of anything in there, but there were a bunch of metal shavings from what it looked like.

A friend and I decided to remove the valve cover to see what could be seen. First, I noticed that a couple of the spark plugs were covered in oil and then the bolts of the valve cover were pretty loose. When we finally popped off the cover, we were able to have a good look at the chain and cam gears and everything started to come together like a Guy Ritchie movie.

All of the cam gear teeth were razor sharp and the chain was able to be pushed down on either side of the guide about 5-10mm. It was very loose. So, everything made sense. The reason the noise happened so suddenly was because the tensioner was so old and because of that, the cam gears were super worn and because of that- on that day that I stopped by a friend's house to pick her up for class- the chain must have slipped a tooth and began the end of the valves. *sigh*

I still have yet to do a compression test, but as soon as I put everything back together and fill it with oil, I'll go ahead and do that and see where I'm at.

Otherwise, I'm on the market for a new m42 or to swap in an m50. I have to research still what that would take.

What does anyone (or just Dave) think?

Geoff · « **Reply #6 on:** November 12, 2011, 10:09:44 AM »

well, even if the compression test is not good news, you could still get your head fixed, or buy a hopefully good used head and replace just that, rather than the whole motor. I guess it depends on how much work you want to do, and how much money you want to spend..if you determine 1 or 2 valves have bent, you could replace those, cam gears, chain, and put it all back together, or buy a good used head with less expense than what it would take to replace the whole motor, not to mention the amount of work..I feel your pain as my new to me 318is just blew a head gasket..but all cars break, thats a fact
Geoff

PeabnutBubber · « **Reply #7 on:** November 21, 2011, 05:27:07 PM »

Ok, so here's the latest update.

I ran a compression test and it looks like cylinders 1, 2, and 3 are at around 200-210 Psi and cylinder #4 kept giving strange results. The most consistent was 180psi but we got 150, 130, and even a 90 and a 30. I think it had something to do with the threading where the spark plug goes possibly, I went and got the compression gauge adapter stuck in there after the first check and maybe some stuff got in there or something when I was trying to get it out. It seemed like the more I tightened the gauge hose the higher the compression read.

Aside from the strange readings from #4, the compression looks really awesome. (My odometer stopped at 159,000 sometime before I bought the car.)

I slapped on a new oil pan gasket, filled it up with oil, threw in some new spark plugs and nice shiny new wires I found at the junkyard on one of the m42's there and got her running for the first time in a while. After leveling out, she had that same rattle, however, all of a sudden the rattle disappeared at idle. Now the rattle is only present when I rev but disappears again after around 3-4000 rpms. This is very interesting indeed. I'm not too sure what this means.

When I opened up the valve cover before, I forgot to check the arrows on the cam gears to see how many teeth it may or may not have jumped. At the junkyard, I found 2 brand new cam gears in the trunk of the 91' with the m42.

I wonder if it is possible to readjust the timing and replace the cam gears without completely removing the chain...

So it looks like I'm just going to be replacing parts in the timing case and hopefully that solves the issue here. I got my girlfriend to get a video of the rattle so I'll include that here.

http://www.youtube.com/watch?v=7knc2n9APlk

again, this noise stopped at idle and now can only be heard when it revs

DesktopDave · « **Reply #8 on:** November 23, 2011, 04:11:31 PM »

Hrmmm. If the chain was that loose I'm still suspecting that it's grinding against something inside the chain case. I'm no expert, but it has a higher pitched rattle that sounds like aluminum contact with the chain. I'm thinking that your motor is OK at idle but once you rev it the chain starts slapping around and you start hearing it.

Good thing you ran the compression test...one less thing it could be. I'm guessing that if one reading wasn't reliable that's still an adequate test result. Certainly better then nothing at all.

I'm still suggesting that you pull the lower cover & check the idler gear, rails & fasteners. The chain has a tendency to eat the plastic bits of the rail or internal parts of the timing case if it's not tensioned properly. I've seen unfortunate M42's that broke parts of the timing case when the tensioner overextended.

FYI, the original M42 tensioner, guides, gaskets and idler gear were all updated by BMW during production to eliminate problems. TSB's went out to dealers and in some cases BMW even issued recalls and fixed the cars at their own expense. I'd recommend that you verify if your car has the updated parts.

PeabnutBubber · « **Reply #9 on:** November 26, 2011, 03:56:16 PM »

Yes, so my next step will be to open up the case completely and get a good look at what's going on in there. I'm going to go ahead and probably replace as much as I can with newer parts. I've read about those updates, so when I go in I'll check and I'll post some pictures of whatever I find.

DesktopDave · « **Reply #10 on:** November 26, 2011, 10:31:48 PM »

Take some pics! It's a bear, I'm told...so I hope this gets you pointed in the right direction.

If you decide to eliminate the idler gear, you'll need an inner case from the later M42/M44 as well.

d.hitchcock · « **Reply #11 on:** December 01, 2011, 09:04:10 AM »

My 318is is exhibiting a bit of timing chain rattle on start-up as well. The sound goes away after a minute or so.

My first thought is the chain tensioner, due to the fact the noise goes away once oil has circulated through the engine.

(But I might be misunderstanding how the tensioner works ... )

Is it worth trying a new tensioner to see if that quiets the engine down?

Thanks,
d.hitchcock

DesktopDave · « **Reply #12 on:** December 01, 2011, 04:31:57 PM »

Are you sure it's not lifter clatter?

I'm getting pretty sure that a new tensioner on an old chain is asking for self-destruction. Check your cam gears. Only if they're good and square (and you don't mind risking worn chain guides) would I'd be tempted to try another tensioner.

d.hitchcock · « **Reply #13 on:** December 01, 2011, 04:48:02 PM »

Excellent, thanks. That's what I needed to hear.

Cheers.
dh

victor.askew · « **Reply #14 on:** December 01, 2011, 07:37:00 PM »

Could this noise be from the fuel injectors, Mine are very loud except at idle.