check valve question.

Message

garysol1 · #1 Post by **garysol1** » Wed May 05, 2004 12:17 pm

We all know that if the oil check valve sticks open that it can make the engine smoke or worse hydrolock on start up. I dont understand...How does the oil find its way into the cylinder? ...past the valve guides.....past the rings.......? Please help me understand this one.

claas900 · #2 Post by **claas900** » Thu May 06, 2004 4:37 am

...id like to know how also..i can understand the case filling up...but getting past eveything..id like to understand...unless somehow it just pushes UP past the rings??

NRath · #3 Post by **NRath** » Thu May 06, 2004 3:59 pm

When they Hydro lock, it can just as likely be happening in the case, not the cylinder. Fill the case with oil, and the piston can't come down. As for the cylinder, it wouldn't take much oil to hydrolock it- I bet 3/4 of a cup would stop the piston in it's tracks.

I've thought the same question as you guys.

garysol1 · #4 Post by **garysol1** » Thu May 06, 2004 4:13 pm

good point about the bottom end hydrolock......but that would not explain the smoking at startup

wistech · #5 Post by **wistech** » Thu May 06, 2004 5:22 pm

There is enough space from the the scavange pump hose to the frame to install a external check valve instead of tearing the engine apart to get at the pump.

Kos462 · #6 Post by **Kos462** » Thu May 06, 2004 10:09 pm

wouldnt that also bend the connecting rod if oil were to get up past the pistion and ya tried to start it

wistech · #7 Post by **wistech** » Fri May 07, 2004 2:38 am

I dont think the starter has enough power to cause that to happen

claas900 · #8 Post by **claas900** » Fri May 07, 2004 3:01 am

...does anyone have a pic of the external check valve?.. Or maybe a part # for one?...

NRath · #9 Post by **NRath** » Mon May 10, 2004 4:46 pm

QUOTE

Originally posted by garysol1
good point about the bottom end hydrolock......but that would not explain the smoking at startup

If the bottom end is full, as the piston comes down, I'm sure the huge pressure that's created would drive some oil past the rings either at the endgap or between ring and cylinder. It doesn't take much oil to make a lot of smoke.

As for the scavenge pump hose, that's a return line to the frame. If your talking about the line from the bottom right up to the top of the frame. The only place it could be put effectively is in the inlet line at the rear oil filter. And a check valve there isn't going to give you what you want. The check valve would only keep oil from exiting the crankcase there, not going in when the engine is off. The check balls in the oil pump work differently than a standard check valve.

wistech · #10 Post by **wistech** » Mon May 10, 2004 4:56 pm

The hose I was refering to was the one coming out of the oil drain plug plate. There is one thing that would work even better. A standpipe that dumps oil into the frame above the level of the oil resivior.. It would eliminate trhe problem right there. You couldnt put a chweck valve in the rear inlet filter because the oil flow is supposed to feed the main pump.