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Discussion Starter · #1 ·
Hi,

I have a '91 Kadett E Caravan 1.7D 42kw.

Brief Description:

After 350.000 km I decided to repair the engine by changing all main components because of low compression and oil consumption.

According to the catalog specifications, all parts starting from cylinder block to cylinder head have been changed.

The camshaft, the rocker arms, the hydraulic lifters and the valve stem seals have been replaced too.

All valves, retainers, springs and the cylinder head are in very good shape. These last parts have not been replaced.

The overload cylinder head oil pressure valve is working fine.

Remark: A qualified team did the job.

The Problem:

When hydraulic lifters are oil empty then the engine has normal compression and all valves work perfectly. For an unknown reason, after some engine cycles, all hydraulic lifters charge with oil at their maximum height and keep the valves opened. For this reason after no more then 4 or 5 cycles the engine has no compression (all valves remain opened by the hydraulic lifters that are oil charged at their maximum height).

Does anyone have any idea about this problem?
Why hydraulic lifters charge so fast and at their maximum height?
What should I do?

Thank you all!
 

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tomking
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Yes, your experienced mechanics set up the rocker arm clearance incorrectly. They should have pressurized the lifters before setting clearance. But they set clearance with NO oil pressure in lifters and hence the settings are wrong on all 8 valves.
 

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Discussion Starter · #3 ·
Hi Tom,

Thank you for the answer.

I'm not very good in mechanics so please correct me if I'm wrong. The meaning of the hydraulic lifters is that they charge with oil according to the valve tail height and other parts fatigue such as camshaft. As far as I know for this kind of engines with hydraulic lifters there is no necessary to manual set up the clearance. The lifters must be oil empty placed and then the clearance sets up automatically after about 15 to 20 minutes of running engine. There is no physical way to manually set up the clearance like it is possible with non-hydraulic lifter engines.

If there is something that I miss then please tell me. This is a desperate situation.

Thank you for your help.
 

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Incorrect rocker adjustment

While running the lifters are pressurized and do not collapse to the bottom (as when unpressurized). A mechanic that is untrained in the opel engine will often use the method that is used to set rockers in a ford V8 - tighten the rocker nut until it stops! So why does this work in the ford? Because the ford rocker stud has a stop the refuses to allow the nut down too far (hence the term non-adjustable).

An Opel has no such stops, so a mechanic using the 'tighten to stop' method will compress the lifter completely. The lifter plug will be slamming down in the lifter cup and mashing the spring - doing incredible damage. As the lifter pressurizes it will refuse to be completely collapsed and all of the valves are then always a bit open. Was fire coming out of your carb and your exhaust sounding like a popcorn popper? Take the valve cover off and rotate thhe crank to each pistons TDC. loosen the rocker nuts for this cylinder and tightnen them until the rocker makes contact with the lifter (no gap) - then one full turn. This depresses the lifter plug one millimeter into its body (only ONE MILLIMETER! not all the way to the bottom)

I'll cross my finger annd hope that your lifters and valves are not damaged.
 

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One has to bear in mind the engine being referred to here in this thread is not a CIH Opel, but rather a 1.7 diesel from a '91 Kadett. I suspect it is OHC-based, so it may not have any adjustment to speak of.

Bob
 

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Discussion Starter · #6 ·
Thank you all for answering.

Yes Bob, you are right. The engine is an OHC-based one so it does not need any rocker adjustments. This is my fault that I did not specify this before.

The question is: what should I do?

I have a theory and I need someone who knows to confirm that it is right or wrong.

On this kind of engine, with automatic adjustable lifters and rockers, the valve spring should be strong enough (when coming back to the released status) to keep the inside lifter spring compressed. Otherwise the lifter will grow up with each cycle until it reaches its maximum height.

Is it possible that the valve springs are a little bit lazy and they can cause this behavior? (why is it happening the same thing with all valves?)
Is it possible that a new valve stem seals set to slow a little bit down the valves when they are released?

Thank you!
 
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