no compression on 2 cylinders, whats it mean?

[performanceisland]

Full 180psi compression on cylinders 1 & 3
No compression on 2 & 4 what does it mean?

[jerrytheautodoctor]

wow, that sucks a bunch! I think I'd probably check the basics like timing first, but that's just me. I have access to a nice video bore scope, so I'd also run that down the spark plug holes with the 90 degree mirror and take a peek at the valve faces, every once in a while I find a burnt valve or hung valve. if you pull the valve cover off (while checking the timing?) take a peek at the valve springs and cams too. realistically the cause for lack of compression is either a lack of air entering the cylinders, a lack of ability to exhaust the spent air in the cylinders, or lack of ability to compress the air (i.e. horrible compression rings, hole in piston, massive head gasket issue etc.)

sorry for your pain

[performanceisland]

Originally Posted by jerrytheautodoctor

wow, that sucks a bunch! I think I'd probably check the basics like timing first, but that's just me. I have access to a nice video bore scope, so I'd also run that down the spark plug holes with the 90 degree mirror and take a peek at the valve faces, every once in a while I find a burnt valve or hung valve. if you pull the valve cover off (while checking the timing?) take a peek at the valve springs and cams too. realistically the cause for lack of compression is either a lack of air entering the cylinders, a lack of ability to exhaust the spent air in the cylinders, or lack of ability to compress the air (i.e. horrible compression rings, hole in piston, massive head gasket issue etc.)

sorry for your pain

i just rebuilt the engine so i am ruling out rings, head gasket, etc. what i am unsure of is how the lifters are opening and closing the valves, maybe my cam is off just slightly not allowing those two cylinders to close the valves, or can it be bad lifters, i am not clear on how these lifters work, someone said the lifters have to be drained before re-install, i reused the lifters, i need direction on how to check the lifters maybe how do i tell if they are opening and closing the valves properly?, i am about to take the valve cover off again so i need to know what to look for, thanks for the help.

[performanceisland]

ok so I am thinking its the lifters not working properly yet, not allowing a valve or two not to fully close, cause at first (after the rebuild) I had no compression on all but one cylinder, 45 psi on 3, after messing around with cranking the engine over several times, now I had full 180psi on 1 and 3, and 0 psi on 2 and 4, I changed absolutely nothing, I have a cheap compression guage from autozone but appears to be working fine, here are my timing pics but I am extremely confident in my timing alignments as I installed just the way it was and all timing marks match up, first lobes are /\ as they are supposed to be, sprockets lined up, etc. Now I have the valve cover off and just out of curiosity I touched and attempted to push on the lifters one by one to see if any one of them moves, from my understanding they shouldn't, but when I got to an intake one on cylinder 2 it moved, pushed in with little force, but then sprang back up and now I cannot push it back down, is this what they refer to that the lifters have to fill back up with oil to function properly and until that happens they wont work right? or is it an indication of a bad one, I always thought a bad one is one that you cannot push to compress when you have it out and in your hand, or one that pushes in but does not come back out. I'm going to recheck compression on cyl 2 tomorrow.

[performanceisland]

have compression on 1, 2 and 3 now, 4 is still no compression, but i see this lifter not looking right at all, anyone can confirm?

[performanceisland]

I just pulled out those two intake lifters off cylinder 4 and these do not compress with fingers at all, so i don't think they are supposed to?

anyone on here know anything about these hydraulic lifters (tappets)?

would't that mean they are one piece solid lifters?

I'm still unclear about how they work and why they say that upon reinstall they wont work properly until oil gets in them or drains out of them? what happens upon reinstall that causes the issue of valves not closing all the way, can anyone clerify, thanks.

[xxxJohnBoyxxx]

Ok I know about these lifters. The picture shows the rocker arm is not engaged correctly on the lifter. There is no way that cylinder will have any compression until those rockers are seated correctly. You can take out the lifter and squeeze it down in a vise. After the motor starts it takes a while for oil to get into the lifters. As you run the motor the lifters will pump up with oil and remove excessive valve lash, otherwise the hydraulic lifters self adjust with oil. For sure that picture shows me the rocker arm is not engaged correctly.

Edit add on: Also the picture shows me the lifter is fully extended and they can get stuck like this when new or when they have not been compressed in a while. With the lifter jammed in the full up position it is very hard for the rocker to engage due to the geometry being off. Also the rocker could be damaged (doubt it but who knows) for some reason and will never engage correctly. My best advice is remove the parts and ensure they will engage each other like your good cylinders. Also crush down those lifters since they do get stuck in full up position. Metric Mechanic told me about doing the lifter crush when assembling and I've never had an issue, but I've only done two M44 heads.

Good luck, John S

[performanceisland]

That makes sense John, and thank you, that's the kind of confirmation I was looking for, I finally found a great video that explained them perfectly and how they work, the key is to have them bled before the install, and if you are going to reuse instead of getting new ones you might as well take them apart and clean them, which is what I just had to do, normally I would just replace them but these are $21 each, that's $336 for the set of 16, I found a great you tube video link that explains and shows in detail how to clean these, I can post here if we are allowed to post links. If you take these apart you can just use a paperclip or solid copper wire to push on the check valve inside to drain and fill with your choice of cleaner.

By the way for those that were doing research like I was and weren't sure what these are called exactly, BMW calls these hydraulic valve clearance adjustment elements or HVAs. I would call it a hydraulic lifter/lash adjuster.

[paul somlo]

Wondering if you could post a link to that video? I've got my head out and would like to clean/verify my HVAs.

Paul
'96ti 232,000mi.