Compression test following screw in inlet manifold

[Cascade360]

Full story here - https://www.pistonheads.com/gassing/topic.asp?h=0&... - thought I would ask for a second opinion on this specialist sub forum.

Short story - rebuilding carb on Peugeot 205 1.4 TU3, dropped screw in inlet manifold, turned engine on, made horrible noise, turned engine off, fished out screw. Engine still runs, but sounds a bit off, only run it for 10s or so since incident. Compression test results dry -

Cylinder 1 - 13.5 bar

Cylinder 2 - 12.5 bar

Cylinder 3 (i.e. the screw cylinder) - 9 bar ...

Cylinder 4 - 14 bar

Little bit of oil in Cylinder 3 and the pressure read 11.2 bar

I've got conflicting opinions on what this means (have a thread on another motoring forum as well) - does higher wet on 3 mean significant valve damage is unlikely the cause of low compression? Could it be a coincidence and it was an old tired engine with low compression on 3 before hand? Is it worth jsut driving it for a bit and seeing what happens? Should I whip the head off and have a look? Rebuilding head may be beyond my skill/patience level but equally it could be a good learning experience.

Thoughts welcome.

[Cascade360]

Just popped the plugs back in - it does run

http://imgur.com/gallery/e3YqfWR

There was a definite rattle on start up and a slight thrum of an odd noise in the background after a minute or so.

[stevieturbo]

Yes you should take the head off....

Whether you actually need to depends whether it is worth that much to you, does it warrant spending time and money etc ?

Or you happy enough to just pod along and see if it gets any worse.

[Stan Weiss]

Do a leak down test. If you don't have the tools to do a leak down test then blow compressed air into the cylinder. This can help show where the compression is leaking from.

Stan

[GreenV8S]

Was the screw inside the chamber?

If you can get an endoscope in there it would be worth checking for signs of valve/piston contact that might potentially have bent a valve. A slight bend might not prevent the valve from sealing but could lead to catastrophic failure later..

[LunarOne]

If you were able to fish the screw out, it can't have got into either the valves or the cylinder, so I'd have thought the horrible noise would have been the screw rattling around in the airflow. If it has caused damage to a valve or a valve seat, that should be fairly trivial to repair with a lapping tool, but the only way to know is to look and you need a borescope/endoscope to check without taking the head off. You can buy these relatively inexpensively on Amazon/eBay. You might want to choose a model which can look sideways/backwards.

[Cascade360]

I fished the screw out of cylinder 3 through the spark plug hole.

I have had a poke about in the cylinder with a borescope:



Sadly can't look backwards to valve

The car has no real value to me, it's a third car I've driven about 5 miles since I bought it last December, so isn't worth spending lots on (on top of what I've already spent probably due me 2k), would rather get rid and buy something else if I can't fix myself as a relatively cheap endeavour and learning experience.

@ Stan Weiss - I have some compressed air but not entirely sure what you're suggesting I do with it ...

[E-bmw]

Cascade360 said:

@ Stan Weiss - I have some compressed air but not entirely sure what you're suggesting I do with it ...

Google "leak down test" quite simple to do with a bit of time.

[stevieturbo]

It's definitely been in there.

A lot of bore scopes have a little mirror attachment so you can see back at the valve. Not perfect, but ok.

Catastrophic valve failure at a later date is possible if a valve is slightly bent...but with reasonably ok compression this would seem unlikely.

[Krikkit]

For how easy it is on the TU I'd have the head off so you can have a good look at the valves etc. I'd guess a slightly bent one now not sealing up properly.

Happy to help if you're anywhere near Chester

[Cascade360]

Krikkit said:

For how easy it is on the TU I'd have the head off so you can have a good look at the valves etc. I'd guess a slightly bent one now not sealing up properly.

Happy to help if you're anywhere near Chester

That's a very kind offer - sadly I'm in London so a fair trek.

I am sure I could get the head off but my concern is I get it off, don't really know what I am looking at, struggle to get it back together, and it sits in pieces on my drive into next year. Or I get it back together and it doesn't work ...

I did take it out for a spin this afternoon. It actually drove really nicely. When hot the exhaust wasn't smoking, but there was certainly a 'thrum' (if that's the word) from the engine, almost like a very quiet intermittent backfire maybe, not experienced enough to know exactly what the noise is.

See if you can hear it in this video - http://imgur.com/gallery/PFUGZBm

Edited by Cascade360 on Thursday 2nd September 17:33

[stevieturbo]

remove the head, give the head to a competent machine shop, let them inspect/repair.

Refit head, without dropping any metal parts into the engine, and job done.

[Old Merc]

Cascade360 said:

I fished the screw out of cylinder 3 through the spark plug hole.

I have had a poke about in the cylinder with a borescope:



Sadly can't look backwards to valve

The car has no real value to me, it's a third car I've driven about 5 miles since I bought it last December, so isn't worth spending lots on (on top of what I've already spent probably due me 2k), would rather get rid and buy something else if I can't fix myself as a relatively cheap endeavour and learning experience.

@ Stan Weiss - I have some compressed air but not entirely sure what you're suggesting I do with it ...

That screw has been “hammered” into the piston crown, so may be it could have affected the top piston ring? Trapped in its groove or even broken.

[Cascade360]

Engine is running fine done a few miles in it over the weekend but there is a definite knocking noise

http://imgur.com/gallery/9Jx1cDR