zero compression

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DingoDog
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zero compression

Post by DingoDog » Thu May 27, 2004 10:55 pm

75 Bus....2L('78)motor...w/hydraulic lifters

On cyl #3, i am getting compression = 0....plug shows small amount of oil on it....when i try to set the valves on #3, the inlet is fine, but on the exhaust, i back it all the way and still get no gap

...so what does that tell me about whats going on in nthere ? and what are my options to try before pulling the head ?

( the Bus sat for a year or two before i got it)

VGM
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Post by VGM » Thu May 27, 2004 11:34 pm

I vote that it's the dreaded dropped valve seat.

DingoDog
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Post by DingoDog » Fri May 28, 2004 2:43 pm

yeah, i guess its the inevitable head replacement......

anyone have a usable driverside head ??

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raygreenwood
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Post by raygreenwood » Sun May 30, 2004 1:46 am

So you remove the screw all the way and still get no gap? Are there any ugly sounds? If yes...possibly a dropped valve. But yes...could be the seat. Check to see if the rocker is up all the way. It could also be a siezed lifet or pushrod pro'blem. Don't put another head in until you get the seats done properly. Ray

DingoDog
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Post by DingoDog » Mon May 31, 2004 11:34 pm

It does not make any real ugly sounds...other than that made by running on 3 cyl.


I remember when i purchased a Vanagon a couple of years back...it made a loud blam-blam-blam....and that turned out to be a sunken valve seat.

This Bus is not making that kind of loud noise...how would i know if it is merely seized lifter ??

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raygreenwood
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Post by raygreenwood » Tue Jun 01, 2004 12:20 am

Turn the engine over by hand with the valve coer off. The rocker should move. Have you checked teh injection connector...and the resistance of the connection? Ray

DingoDog
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Post by DingoDog » Tue Jun 01, 2004 1:49 pm

...Ray...not sure how to watch rocker and turn pulley at same time..

anyway, this is what i did...it may or may not be relevant...

i turned the adjusting screw so that it just touches, then backed it off one full turn, exactly....then i turned the pulley 360 degrees, and checked the adjusting screw...every time there is a discrepancy of about 80-90 degrees of turn on the screw.....less or more depending on whether i start on top-dead#1 or topdead#3

so in my primitive logic, it seems the valve itself is moving in and out a small amount...although i can never get the rocker to open or move at all

does this tell me anything ?

DingoDog
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Post by DingoDog » Tue Jun 01, 2004 2:38 pm

Ok, after removing some shroud...I spied on the rocker while turning the pulley...it seems to move naturally like the other three...however ,with
screw backed off all the way, i still cannot get a gap i.e. cannot rock it back and forth by hand like the others

anyway, i removed the rocker and to my surprise the part # turned out to be 371B, which according to Wilson is a Vanagon square-port....i had just bought three used round-holers...guess i learned my lesson..hehe!

alsehendo
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Post by alsehendo » Wed Jun 02, 2004 1:13 am

Just pull off rocker stand and lay a flat edje across the top of the valve stems if the un-adjustable one is way diffrent I woulld vote dropped seat also. The seat can go down into head as well as come loose. Yank the pushrod tube and pushrod and lifter and look at them. You don't have to pull head to do this. Swap poop around, (rocker shafts two in each head! excetra) and see if no compression problem / adjustment problem moves; just put everything back before you start it again.

DingoDog
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Post by DingoDog » Wed Jun 02, 2004 2:14 pm

how much is 'way different' ? there is definately a difference, but not that much

anyways, i removed the pushrod and pried out the lifter, which i am looking at right now....How do i determine if this is the culprit...is it possible that it just no longer acts hydraulically ?

alsehendo
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Post by alsehendo » Wed Jun 02, 2004 4:08 pm

Mostly dose the adjustment . compression problem move when you swap rocker arm shafts and all their components; the exaust pushrods and lifters from one cylinder to the other? If it dose move do one at a time untill you find the culprate. I would actualy do the intake at the same time just to elimnate them form compression problem it could be diffrent than adjustment problem but not likell--so recheck with compression gage.

Chances are problem will stay with the same cylynder. If it dose not move put them back and bite the bullet and pull the head.

Your trying to see if your adjustment / compession problem moves to other cylinder if it dose not move it's the seat or maybe a hole burt in piston or broken ring--something other than rocket pushrod or lifter. Process of elimination! If the lifters arnt stuck doing all this is not too hard and worth trying before you pop the head.

Don't start it this way just see if the adjustmaent / compression moves to other cylinder.

Remmber if you can't get a gap you could be forcing the exaust valve open all the time hard to pump up compression this way.


Trying to adjust valve
Rotate crank by hand untill the roterlines up with the spark plug wire on cap that goes to the cyliners valves your are adjust this is close enough if you know the distributer is set up corectly. If you dont double check by sticking something down # one rotate engine till you feel piston at TDC and see if roter lines up with # 1 wire and line on distributor. Don't trust the marks on the fan!!!!!!!!!!

PUT EVERYTHING BACK BEFORE YOU START ENGINE AGAIN.

alsehendo
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Post by alsehendo » Wed Jun 02, 2004 4:20 pm

I have done this but I asume you could take compression test with rocker shafts and arms and all removed from the bad cylynder to see if that hole would pump up you meter when you turn the engine over. IF you still got no compression or very little it would automaticly meen something inside because both valves would definatly be shut all the way and not held open by inability to get gap in adjustment.

Rember to remove distributor wire so it won't start this way on other 3

DingoDog
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Post by DingoDog » Wed Jun 02, 2004 7:08 pm

Ok, i think that all makes sense.

I put the exhaust lifter from #4 into the #3 exhaust slot...and now i get a gap and am able to adjust.

After coffee break, i will check for compression.

Thanks for your help.

alsehendo
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Post by alsehendo » Wed Jun 02, 2004 9:33 pm

I have had lots of problems with these lifters especialy if they have been sitting in engine not running for a long time and I do prime them like the book says.. Sometimes they are sorta half ass after rebuld and quit working after a month or so. Get yourself a used hydro and cam and a set on ebay they go realy cheep and as you can see are easy to swap out.

DingoDog
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Post by DingoDog » Thu Jun 03, 2004 3:02 pm

switching the lifters around didnt make any diffference....so i went ahead and pulled the head...sure enough, the old valve seat had sunk in...

Anyway thanks for your help....i learned quite a bit along the way

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