Hi

You learn something new every day! I had always used a compression tester that gave a pretty good indication when readings were compared cylinder to cylinder but I can see that, with proper equipment, this test could be meaningful as well but relied on valves being closed and the crankshaft not rotating.

I will chat with the service place when I collect the car tonight and will try to clarify some of the statements he made that flagged warnings in my head.

 

I took my valve covers apart recently and cleaned them and, like a previous poster, I don't see how you could get a scope to the rockers because of a shield (which I took off and cleaned, and replaced).

I would take the four bolts off and look at the rockers yourself. Take 10 minutes. If they are dry, then the passages are blocked or the oil pump isn't doing its job; but if the latter, I think you'd have bigger problems and you would have heard scraping and crunching when you turn it over.

 

Our factory tester does a compression test at the push of a button. we use smoke to narrow down what was leaking. Pump smoke into the cylinder with all valves closed. If it comes out the intake, you have intake valves leaking. If it comes out the exhaust, exhaust valves are leaking. If it comes out the next cylinder. head-gasket or cracked head. Comes out the oil cap, worn rings.

One case was a cracked head. the other was scoring on the cylinder walls wasn't giving the rings a good seal. That car got a new engine.

 

Hi

The scoring issue interested me.

Decades ago in the uk, if this was an issue I would have the cylinders rebored and oversize Hepolite Pep pistons fitted that had extra rings including an oil control ring near the base of the piston .
That was an alternative to a new engine.

Correction due to memory playing tricks.... I have had engines rebored but just use standard oversize pistons.

The Hepolite Pep pistons was a trick my father showed me... they were designed to bring new life into old worn out engines. They had a stepped rim dodger top compression seal ring along with additional compression and scraper rings below and the extra oil control ring at the base of the piston.

This link rather shows my age....http://www.oldclassiccar.co.uk/hepolite.htm

 

Warranty runs differently. In addition Mercedes engines have some type of liner that we dont have the equipment to replace. They are they only ones that can, as far as I know. No one really knows how the liners are attached either. And all our engines get sent back to German for some reason.