Updated: Valve Leaking Problems

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Derflandhumus

New Member
Messages
6
Currently working on 1uz-fe non-vvti out of an LS400 1994

Engine wasn't really running when i got it, found out there was 0 compression on one of the cylinders and found out something had gotten in there and dinged up the cylinder head to the point where the rings were seized, it also ruined the cylinder head and bent an intake valve.

So after replacing piston and replacing head I then decide to do a valve job, after replacing most of the crap on this thing before putting the timing belt on, i decide to test the compression with a leak down

I used 100PSI and here are the results (dry)

Front to rear

left
1. 95/100
2. 80/100
3. 95/100
4. 94/100

right
1. 91/100
2. 57/100
3. 90/100
4. 75/100

I can feel air come out of both intake and exhaust on every single cylinder

I made sure the lobes were on the side or rear so as to not depress the bucket before you ask, and the crank position should not matter as its non-interference. I also did a valve adjustment before this so none are tighter than the tolerances in the official repair manual. I also lapped all the valves.

So did i do a piss poor job at doing lapping the valves or am i missing something? cause i spent literal hours doing that shit and i dont really care to do it again.

Just wondering if anyone had any thoughts, I watched one of glovermans videos and he mentioned that its a waste of time doing a leak down test on a cold engine? Could someone elaborate as to why?


EDIT:

Ok so I did a wet test today and messed with the cams a bit and i got these results:


Front to rear

left
1. 93/100 (-2)
2. 88/100 (+8)
3. 95/100 (+3)
4. 94/100 (+2)

right
1. 94 /100 (+3)
2. 91/100 (+34)
3. 94/100 (+4)
4. 84/100 (+9)

So overall looking alot better esp on right #2

However when i first got this vehicle i did a leak down test then (before ANY work was done) on all cylinders and this was my result:

Note: only used 50psi to test

Front to rear

left
1. 47/50
2. 47/50
3. 47/50
4. 48/50

right
1. 47/50
2. 0/50 (dead cylinder with damaged valve)
3. 48/50
4. 48/50

So looking at this, seemingly before the lapping it was better sealed prior to any work being done, considering how bad those valves looked i struggle to understand how.

I also replaced all valve stems so that isn't an issue, and i can still feel the air leaking out of the intake and exhaust ports.

So based on this information, should i pull off the head and try to relap? or just run with it?

Thanks
 
Last edited:

ivan129

BlownZX
Messages
186
Location
Some where down under
Did you clean off all the grinding compound from the surface of the valve heads and seats after lapping them in? If not, that could explain leaks across all your valves.
 
Last edited:

Derflandhumus

New Member
Messages
6
Did you clean off all the grinding compound from the surface of the valve heads and seats after lapping them in? If not, that could explain leaks across all your valves.

Yeah, i used a towel and then made sure there was nothing by wiping with a microfiber cloth thoroughly if thats what you mean.
 

ivan129

BlownZX
Messages
186
Location
Some where down under
Mmm, not the way I would have cleaned the valves, seats and heads. However given where you are now; do a comp test, dry, then squirt 2 shots of oil from your oil can into each plug hole. Crank the engine for 20- 30 secs to get the oil sloshed around on the bore walls and over the valves and valve seats. Do another comp test again and post your results.
 
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