2.5 6 cylinder---> NO COMPRESSION!!!

[tre5seven]

I just bought a 95 525 that barely runs. I got a steal of a deal on it and I work on cars for a living anyway, so I thought I would scoop it up and try to have a neat car that is paid for. When turning it over, it sounds like it doesn't have much compression on at least one cylinder..maybe more. I pulled the valve cover and nothing looks bent or broken....

Can someone tell me if there is anything that these cars are notorious for that might be whats wrong with mine before I tear this thing down to bear bones?

What is the spec for compression on this engine?

Any help would be greatly appreciated!!!

 

[m5runner]

That motor isn't known for having compression problems to tell you the truth. I don't think most to any BMW's do. If you put a compression gauge on it, you should get anywhere between 90 and 120. I don't have the specs infront of me but that's what my 325i had when the compression test was done a while back. I would do a compression test before I pull anything apart.

 

[Cody318]

When i tested compression on my 92 525i i came up with about 210-220 psi per cylinder over four full compression cycles, though I think my guage was a little funny because that seems very high to me (especially with 180k miles). I would not be too surprised, however if you have a faulty cylinder head gasket causing localized low compression in one or two cylinders.

 

[m5runner]

This is true. Looking at that spark plugs can give you an idea if something is wrong with the entire ingnition cycle. Mine was running on 5 cylinders a few years ago and it turned out to be the brain box. Look at the plugs and see if you see fuel on them and you can narrow down which cylinder it is. swap the coils around and see if that changes for that particular cylinder and go from there.

 

[bimmertech2]

The first thing to do would be to perform a compression check the psi would be around 100 to 120 psi. if you find a low compression issue a lot of the time the engine has been over heated and the head is warped. if you tear the motor down and find the head is warped have sombody checked the block with a straigth edge to make sure there is no damage to the block. As far as problems with this cars. oil leaks, frt end suspension problems, struts bushings tierods, center link. normal stuff let me know how it turns out.

 

[atl530i]

Your readings should around 220psi. The M50/M50tu CR is 10.5:1. The spread between all cylinders is also important. Between all 6 cylinders, there should be around a 10% or less variance.

Your readings suggest worn piston rings, bad valve, blown head gasket, or a warped head.

Your readings were correct Cody318.