Vauxhall Astra compression loss - Ti mbo
Following a top end rebuild on my Astra 1.8 sxi as a result of the water pump failing causing valve damage etc, it now has difficulty in starting. Once started it runs fine. The mechanic states there is a loss of compression on starting which should rectify itself once the valves have run in and built up a layer of carbon etc. Is he correct or am I on a loser.
Vauxhall Astra compression loss - 659FBE
Badly rebuilt engine - valves probably not lapped in.

659.

(If he was right, no new car would run properly).
Vauxhall Astra compression loss - Number_Cruncher
I wouldn't be surprised if it was badly rebuilt engine - some valves still bent!

Number_Cruncher
Vauxhall Astra compression loss - Ti mbo
The garage in question has an excellent reputation and came well recommended. He changed all the valves and showed me the old ones. I do not doubt the damaged valves were from my vehicle. Once it starts it runs fine which I assume would not happen if it was a bad rebuild. The hotter the engine, the easier it is to start.
Vauxhall Astra compression loss - Ti mbo
Could it be that the piston rings could have been damaged also.
Vauxhall Astra compression loss - Ruperts Trooper
Shoot the mechanic, nuke the garage!

Your engine has been rebuilt badly and you're being fed rubbish to try and hide that.

There's no such thing as a reputable dealer. When my Cavalier 2.0 16v had to be rebuilt, following a cambelt failure, I entrusted the work to my local Vauxhall dealer - bad move. Both manifolds leaked and the stretch head bolts had been re-used - a no-no on any Vauxhall and many others.

When the rebuild had been redone the engine was fine, better than before, obviously benefitting from new valves and BETTER compression.
Vauxhall Astra compression loss - Number_Cruncher
There is one possibility that might actually be OK, and not an inexcusable error on the garage's behalf..

On the older 8v engines, if you didn't flush the old oil out of the hydraulic lifters and empty them while the top end was apart, they would hold the valves open a bit, until the pressure from the valve springs eventually forced the excess oil back out of the lifters. My apprentice at the time did a top end of a 1600 Cavalier up at home for a member of his family, and he forgot to drain the lifters. The car didn't start for three days! He hasn't forgotten to empty them since!

On the newer 16v engines, the lifters are much easier to empty than the older design, but I suspect it is still possible to have them jack up upon removal.

If this is the case, it may settle down over the next few days.

How old is the car? How does it run once it is going? As well as before? As smoothly at tick over as before?

Number_Cruncher
Vauxhall Astra compression loss - 659FBE
"Pumped up" hydraulic tappets will very quickly resume their correct operating clearances if the engine can be started (hopefully without damaging the valves in the process). When the oil is hot, the tappets need a continuous flow of pressurised oil to maintain correct operation - without this the tappets will become very noisy, very quickly.

I hope the mechanic didn't bend the new valves on the first start-up. Compression test needed I think.

659.
Vauxhall Astra compression loss - braindead
def bad rebuild (valves self bedding hmmm! )
Vauxhall Astra compression loss - Ti mbo
Thanks for the replies. The engine does start eventually and the hotter the engine the easier it is to start. It seems to turn over twice and then I feel it should fire but it cant seem to manage it. Then it takes probably 6-8 seconds of turning to eventually fire (seems like a lifetime). When running it is fine. Idles nice and quiet, accelerates fine,no flat spots etc. On a run it seems like the damage never happened. It is a 2000 x reg 1.8 sxi. A compression test has been carried out and apparently it is down on 2 cylinders. This is where I was told it should eventually build up over a couple of weeks.
Vauxhall Astra compression loss - Ti mbo
It has been suggested to me that it may be the cam shaft sensor not working correctly. Any ideas. Thanks
Vauxhall Astra compression loss - Grease_monkey
You have already said that a compression test has revealed that 2 cylinders are down on compression. Did he tell you what the compression was? I'd imagine he is just hoping that the bodge of a repair he has done on your cylinder head will eventually sort it self out once the engine has been used for a while. Take it back and demand that he rechecks his work.
 

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