Pressurising In The Sump

[dcc 855]

The engine is still in the car, as after I failed to get it to start, took it to a friendly mechanic to ask him to check it out for me.

 

He asked what had been replaced durring the rebuild.

 

Honed liners

new piston rings

liners reseated with new orings

new main shells

 

other than fluids and gaskets, think thats about as far as I went.

 

Now when trying to start the engine, the sump is pressurising, my first thoughts was the piston rings. they were bought and fitted at a professional machine shop in South Wales, so I trust them to be fitted and honed properly. I cant see how the liner would cause the lower end to build pressure, as there is in theory, no way for the pressure to get past the piston rings if they are known good condition.

 

Any thoughts on what the cause is?

 

I wont have the car back untill later in the week to drop the block back out to check everything. but im fairly sure that everything went back in as it should, especially the liners. I used some grease to help them fit and seal to the block. the block showed no signs of wear or corrosion arroudn the base of the liner seat. the liners also had minor protrusion from the block surface.

 

Many thanks for reading and any help offered will be a godsend,

Dan

[welshpug 1,657]

has it been run in yet?

 

are the breathers in good condition?

[dcc 855]

The breathers are not collapsed, and are all intact - no splits etc..

 

As for being "run In" - the engine hasnt been started yet - so I dont think so. I am just wondering, if i have over tightened the mains caps, would that give the same effect/feeling as a pressurised sump?

[welshpug 1,657]

so how do you know its pressurising?!

[Tom Fenton 1,542]

The rings won't seal well until they've bedded in. Get some miles on it.

[dcc 855]

so how do you know its pressurising?!

 

This is what I have been told by the mechanic who has been checking it over.

[brumster 135 1 Cars]

Short of a collapsed/blocked vent pipe, the only times I've seen the bottom end get pressurised is rings, or rather catastrophic head gasket failure (the latter blowing the oil all over the underside of my nice clean bonnet!). Wouldn't a compression test of the cylinders tell you the state of this? ie. low compression in the cylinder, or leakdown over time, would explain the pressurised crankcase....?

[mattmk1 0]

Rings, but if it hast been run yet then they wont be fully bedded in, but even so it shouldnt be building sump pressure to any noticeable extent. Unless there is absolutely zero compression then it will start even if its pressurising the sump, as the pressure will breathe. So id say the mechanic sounds a bit dubious. He should have compression tested it to get a better idea.

[luggy 13]

Hey Dan!

I think swinney had a similar issue with crankcase overpressurising with oil coming out of the filler, dont know if he resolved it, I believe he's just put the head back on his Mi.