Hydraulic Lash Adjusters...How do they work? 1

[tyratfou]

Hey everyone. I have a 1985 Toyota Celica/Supra with the 5M-GE engine. It uses hla's and ive been getting a horible ticking sound, reduced power that sometimes feels like it kicks in under load but cant quite sustain it. It sounds exactly like a cracked ex. manifold would. With a stethescope, i found that the valve covers were the source, the intake side being worse. I pulled the ex side off with the engine just shut off. I was able to make them click by pressing on 4 out of 6. But later when the engine cooled, i could only barely make one click. Another thing, when i start the engine, it gives that very distinct sound of an egine with 0 compression. It will do this for maybe a second or two and the engine starts.

Sooooo...how do they work? Whats the ins and outs? I know the oil pressure regulator feeds oils to them that pushes them up in the bore to create a constant zero valve lash, but how does oil cycle around to the inside. Also, how do i inspect them? Tons of articles on bleeding, but theres so much more going on. Thanks for all your help in advance.

 

[Lou Scannon]

Your best bet is to get a factory service manual for your vehicle and follow the diagnosis & repair procedures.

 

[L4189]

If it is the lash adjusters clicking away then they are no longer pumping up because they plugged up or just jammed. Best to replace them. There is something called a leak down test that is performed on a test machine that collapses a full lash adjuster. On some types of engines too fast as well as too slow can cause problems.

 

[tyratfou]

I have the manual but i was hoping to find principles of operation type of thing...

 

[Lou Scannon]

It's not very complicated. The internal cylinder is fed with pressurized oil. There is a check valve that closes when oil tries to go back out the inlet port - this happens each time the cam lobe starts to push on the adjuster.
If the adjuster leaks too much, it will compress and be noisy.
If the adjuster is seized internally, it will either not adjust and be noisy, or it will hold the valve off the seat and cause it to burn.
Those are the main failure modes.

 

[DanEE]

The oil galleys in the head on this engine were quite small and if oil not maintained/changed, they can plug up...

Check the cam lobes and bearings for excessive wear/scoring...

If you see it, the galley's are likely plugged up and probably also starving the lifters..

 

[BrianGar]

In very simple terms all the buckets are are just very small little hydraulic bottle jacks between the cam and valve stem, when the cam lobe faces up(valve closed) the hole in the side of the bucket is oppisite the oil drilling in the tappets bore in the cylinder head, oil flows in here to the bucket and fills the little hydraulic jack, taking up any play between the cam and the valve stem, the engines oil pressure isent strong enough to pump them up so far causing the valves to open, they just contain enough pressure to take up any play.(interesting point here as a few years back geo had an engine doing funny things, it turned out that the oil pressure regulator valve in the oil pump had stuck causing very high oil pressure which in turn was actually pumping up the tappets too much causing the valves to open and compression to be lost)
Each bucket contains a one way valve where the oil enters so that when the cam comes to open the valve the oil cannot escape and the little ''bottle jack'' stays the same length/height.
Now thats all very well when their working but after a few years this little non return ball valve gets all mucked up with dirt causing it to stay open, and when the cam comes round to open the valve all the oil that has been pumped into the tappet escapes out the non return valve again, causing the tappet to empty and start hammering, thats the ticking you hear from the top when this happens.


See images attached for further info, I found them...eventually..

http://i150.photobucket.com/albums/s92/chippievw/hydraulicTappets0011.jpg

http://i150.photobucket.com/albums/s92/chippievw/hydraulicTappets0021.jpg

I hope the links work...If not, Ill rehost.

Brian,