Author Topic: few engine questions... (Read 6229 times)

B318M42W · « **on:** November 08, 2008, 11:55:36 AM »

I have a few questions and concerns with my engine...
1) some coolant finds it's way into the oil, but the engine isn't burning abnormal oil quantities or any coolant. Last know compressions were about 210 psi, where's the leak???

2) how reliable is the timing chain on the M42? car has about 175 000 miles ont it. do they break a lot? are the sprockets subject to failure wear? any operational restrictions until it's fixed??? and in the event it snaps, how much does a head go for these days???

Thanks for any imput!

B318M42W · « **Reply #1 on:** November 13, 2008, 06:13:19 PM »

bearsbmw · « **Reply #2 on:** November 13, 2008, 06:25:12 PM »

if your timing chain snap's you will need alot more then just a head lol

roundel318 · « **Reply #3 on:** November 13, 2008, 07:14:57 PM »

Stock timing chain is double row, it's not bad, just keep the tensioner replaced when needed, there is also a guide that sometimes needs to be replaced.
I am no big expert on the coolant in the oil, but it could be a head gasket or timing profile gasket (the 1 big flaw) among other things I suppose.
Most profile gaskets failed within 100,000 miles from the factory and many were replaced under warranty, haven't really heard from a replacement failing.

KenC · « **Reply #4 on:** November 13, 2008, 07:27:44 PM »

Coolant leak may be coming from the profile gasket.

sprockets and chain are prone to wear... never heard of a chain snapping though. Just make sure to keep up on the tensioners.

B318M42W · « **Reply #5 on:** November 13, 2008, 08:29:50 PM »

Thanks for all the input! Tensioner was replaced about 5K miles ago... should be good for a while...
coolant flush with a thing that seals holes in the cooling system will hopefully buy me a few months until I decide to undertake the replacement of the profile and head gasket...

strad · « **Reply #6 on:** November 13, 2008, 10:13:40 PM »

Never mind how reliable the timing components have been for other people. Have you pulled the valve cover and done an inspection of the sprockets? Have you pulled the oil pan and looked for loose bits in it? At 175k, it's definitely time for you to undertake those two activities. Check for properly torqued upper pan bolts while you're in there -- that's another M42 killer.

B318M42W · « **Reply #7 on:** November 14, 2008, 06:47:10 AM »

I was thinking on having a look at the chain/sprockets when i get a chance in about 2 months, (car is not a DD...) How can I tell if it's excessively worn out? places that are more a good idea to check out?? to take out the lower oil pan, do i need to remove the subframe crosmember??

Thanks again!

twright · « **Reply #8 on:** November 14, 2008, 03:38:31 PM »

The new sprockets are flat on the outermost diameter. This flat spot is about 1.5 mm wide. The worn out sprockets don't have a flat spot, they come to a point.

cecotto · « **Reply #9 on:** November 14, 2008, 04:41:28 PM »

Quote from: B318M42W;60222

I have a few questions and concerns with my engine...
1) some coolant finds it's way into the oil, but the engine isn't burning abnormal oil quantities or any coolant. Last know compressions were about 210 psi, where's the leak???

2) how reliable is the timing chain on the M42? car has about 175 000 miles ont it. do they break a lot? are the sprockets subject to failure wear? any operational restrictions until it's fixed??? and in the event it snaps, how much does a head go for these days???

Thanks for any imput!

1) Are you sure it's coolant.. what season are you in? It could be condensation. If you're not loosing coolant it might not be coolant, but condensation... It might also be coolant in a small quantity. Your leak might not be large. It really can be hard to tell. Can you really tell if you loose 50-100cc ?

2) I've never heard of a chain snapping. But i have experienced a failure of the tensioner, together with the rails. I have heard a lot of others experience this. Actually on my desk right now i have a oilpump housing with evidence of a failed intake side chain guide "It has chain scuffing marks, that would not be possible with an intact guide". When the engine i'm now driving had this incident i drove it home approximately 50km. It sounded awefull, but it didn't do any other damage to my engine.. But if you can avoid driving when it fail i would prefer that.

The timing chain on a M42 comes cheap, so if it has an unknown history and high mileage i'd change it out. as a comparison the timing chain assembly on a S14 engine is very expensive you can pay above 700 USD just for the essentias.

B318M42W · « **Reply #10 on:** November 14, 2008, 04:53:28 PM »

the reason why i think that it's coolant that just seeps though is that normally when i redline it a few times, the oil get a little more clearer, and seems to have a small change in viscosity (more water like feeling to it). also, after an oil change, i skim an object at the surface and it leaves behind a trail, that's lighter in colour and then resorbs itself back to the "original" state. I did notice last winter that the coolant level went down a little (about 1cm per 400 miles). also, (maybe not related...) the oil smells bad, a bit like exaust and gas. oh and the engine has a tendency to groan upon starting and then a little bit around 1500-1800 RPM.

cecotto · « **Reply #11 on:** November 14, 2008, 05:00:55 PM »

Quote from: B318M42W;60748

the reason why i think that it's coolant that just seeps though is that normally when i redline it a few times, the oil get a little more clearer, and seems to have a small change in viscosity (more water like feeling to it). also, after an oil change, i skim an object at the surface and it leaves behind a trail, that's lighter in colour and then resorbs itself back to the "original" state. I did notice last winter that the coolant level went down a little (about 1cm per 400 miles). also, (maybe not related...) the oil smells bad, a bit like exaust and gas. oh and the engine has a tendency to groan upon starting and then a little bit around 1500-1800 RPM.

water often produces a brown gue / sludge inside the engine...

try (with the engine turned off) to stick your finger inside the engine through the oilfiller hole and see if theres any such deposits to be found....

Alternatively you can remove the cam cover and inspect it this way..

B318M42W · « **Reply #12 on:** November 14, 2008, 05:07:21 PM »

interesting! i'll remove the vavle cover and keep an eye out for the deposits at the same time as the timing components inspection... (that should be after x-mas.. don't have the car right now

)

Selfish · « **Reply #13 on:** December 11, 2008, 11:45:39 PM »

I replaced my valve cover gasket 2 days ago, since I was going to change the oil anyway and some of the bolts on the valve cover were not properly torqued, and I also checked the lower oil pan while I was at it, and found 3 screws lying on it. I heard it is not uncommon, nor good, since it may affect the oil pickup, depending on which bolts are loose, I believe. It all took longer than I would have wanted, but in the end I managed to put it all back together. No apparent damage or anything wrong when removed the valve cover. Engine was running smoother afterwards, but to my surprise now there�s a leak. Not from the valve cover gasket (as it was before, that�s what led me to this), haven�t been able to pinpoint where from since it has been raining for the last 2 days. What weirds me out is the yellowish/greenish-oily stuff that leaks from my car. I�m assuming there�s coolant leaking into the engine. But where�s it leaking in there through? and where is leaking it out from? I might be able to figure all this out tomorrow �cause I don�t have to work. It smells very lightly like burnt oil, there�s no overheating. Is it too bad to drive a few miles here and there before I get this fixed?

B318M42W · « **Reply #14 on:** December 12, 2008, 07:03:59 PM »

I also have that kind of burnt/overheated oil smell from the oil. I've tried lubromoly 10w40 semisynthetic oil and a more "regular" oil and it still smell... It's been running like that for the past year or so (or about 15K miles). In my opinion, I think that the oil gets that smell from the blowby exhaust gases from the cylinder???