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reasons to change your timing belt on a m20

7K views 29 replies 12 participants last post by  south26 
#1 · (Edited)
Hi, I was taking a head off a m20 from a e34. I bought the car to part out. I was told that it had a blown head gasket. Well I have never seen a gasket go like this. I did not count but a number of rockers broke. 6 valves broke, one stuck in a piston. 4 out of the 6 pistons had holes in them.











Remember change your timing belt.

Andy
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#9 ·
Ahhhh .... the joys of an interference engine with a timing belt (that is not properly maintained/changed out) :cry:
 
#15 ·
Thats what costed me my first car and second car.. Cruising along then all the sudden SNAP!

Time for a new car.. Hadnt gottn into swapping yet.. Seemed to hard back then lol
 
#23 ·
Belt/ chain

As all know BMW used a timing chain in most motors. Even the chain can be a disaster if you don't keep up with the tensioners. The M50's had a double roller timing chain with a mid engine gear on a bearing to take the stress of the chain. My 740IL didn't have that gear, instead, BMW just used plastic chain guides and as such, many failed as a result. BMW must have saved hundreds per car, but their customers (and reputation) lost thousands. I am sure they saved a few bucks using a belt on the M20's also. My advice is to change your tensioners and / or belt often, even more often then you might think you might need too, cheap insurance IMHO:)
 
#24 ·
As all know BMW used a timing chain in most motors. Even the chain can be a disaster if you don't keep up with the tensioners. The M50's had a double roller timing chain with a mid engine gear on a bearing to take the stress of the chain. My 740IL didn't have that gear, instead, BMW just used plastic chain guides and as such, many failed as a result. BMW must have saved hundreds per car, but their customers (and reputation) lost thousands. I am sure they saved a few bucks using a belt on the M20's also. My advice is to change your tensioners and / or belt often, even more often then you might think you might need too, cheap insurance IMHO:)
I think you might be over stating the fact about the chain. It is not a common problem and yes can happen but not likely. As to saving hundreds? The m20 with the belt was built to be less of a gas hog compared to the m30, which it was. The belt was suppose to deal with the closer specs compared to the 60s tech that made the m30. I have driven a car with the m30 and have never worried about the chain. I have parted 26 BMWs and have never parted one because of a failed chain., 5 of those had a failed belt. So yes a chain guide can fail but not likely.

Andy
 
#25 ·
Belts VS Chains

Well, you missed my point. It was that chains are much better "IF" properly maintained and don't suffer from a poor design. But I am sure after junking so many BMW's you already know what the major design timing chain flaw was in the M60 0ver the M50. I only have 40 years of fixing and racing cars and bikes under my belt, junking must be much harder and I am sure you learn more by tacking one apart, then by making them run, thanks for setting me strait, I will junk my car tomorrow;)
 
#26 ·
Your point might have been to replace parts when they are needed, but instead made it sound much more likely that the chain would break. My point was that in all of the cars I have taken apart I have never seen a problem. Also never said it was easier to take fix a car then part it. If you want to junk your car that is your choice. The whole point of this thread is to help people. M

Andy
 
#27 ·
M62



Me too, most BMW timing chain designs were great, even going back to WW2 times. But for some reason on the M62 and other V8 motors they decided to negate the idler gear at the lowest and most stressed place the chain travels and replacer it with a plastic runner :yikes:
The M50 and others had the idler gear and almost never have a failed timing chain, but many 740's and others have died and gone to heaven due to the newer design :angel:

Here is a link to a short video that shows just what I am warning other BMW owners to be aware of for their own sakes. My 740 M62 never failed even at 240k miles, but I kept the oil fresh and I changed the timing chain adjusters before any slack and ware could happen. If the link doesn't come through anyone can just google BMW M62 timing chain failure and there will be tons of video's and write ups on it. That is because the are tons of M62 motors in the junk yards. My 530i M50 has the idler gear, so I decided not to junk it just yet, it only has a quarter million miles on it so far ;)

https://www.youtube.com/watch?v=qkihFnaPLYw
 
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