No valve clearance (1 Viewer)

[mbashier]

Hi everybody, I’ve greatly benefited from you guys whether from direct advice or from reading through previous threads. I’ve come upon a problem that I haven’t found posted before. I’ve lost compression on cylinder #5 to about 20 psi. Prior it was about 110 psi and all other cylinders were about 150psi. Squirting oil in through the spark plug hole didn’t help, so I’m thinking it’s a valve problem. I tried adjusting the valve on cylinder # 5 just to be sure it’s not a valve adjustment issue. But when I tried adjusting there is no clearance even when I tried unscrewing to the very end the valve is still pushing up with no way for the feeler to check. It’s been like this since I first got the truck and tried adjusting the valves about 2 years ago. I’m planning on pulling the head now but what should I expect or look for other than the obvious seating of the valve or valve damage? This is currently my DD hence asking to keep downtime as short as possible. Thanks

 

[Rusty Marlin]

No compression and the valve stem is free to travel to the limits of the adjustment.
Worst case, the valve head is broken off and embedded into the top of the piston.
Best case, the seat in the head and on the valve head is burnt out to the point they don't touch anymore.

Either way, pics please.

 

[fjbj40]

Hi everybody, I’ve greatly benefited from you guys whether from direct advice or from reading through previous threads. I’ve come upon a problem that I haven’t found posted before. I’ve lost compression on cylinder #5 to about 20 psi. Prior it was about 110 psi and all other cylinders were about 150psi. Squirting oil in through the spark plug hole didn’t help, so I’m thinking it’s a valve problem. I tried adjusting the valve on cylinder # 5 just to be sure it’s not a valve adjustment issue. But when I tried adjusting there is no clearance even when I tried unscrewing to the very end the valve is still pushing up with no way for the feeler to check. It’s been like this since I first got the truck and tried adjusting the valves about 2 years ago. I’m planning on pulling the head now but what should I expect or look for other than the obvious seating of the valve or valve damage? This is currently my DD hence asking to keep downtime as short as possible. Thanks

I’m curious as to what engine you are talking about

 

[Rusty Marlin]

Obviously a push rod of some sort...

 

[BILT4ME]

I’m curious as to what engine you are talking about

Based on his sig line, it's either a 91 FJ80 3F-E or a 79 FJ40, 2F. Either way, a push rod version.

Benghazi, Libya, BTW

 

[fjbj40]

I figured a pushrod engine, it would be nice if folks would say what machine they are talking about is my point.

It could also just be a stuck valve and not catastrophic failure!

Pushrod/lifter side cover would reveal answers before head removal!

I find people typically think the worst before fully troubleshooting .

cheers

 

[mbashier]

Oh I’m so sorry I forgot to state a US market 3fe .

 

[mbashier]

I’ll definitely post pics of what the source of the problem was. Hoping it’s something obvious and not something that's going to turn into a rabbit hole.

Should’ve occurred to me to inspect the lifters from the side cover, but now I’ve got just about everything off with a sore thumb and several nicks to prove it. But will change the side cover gasket anyway for good measure.

Any other places to keep my eyes on that could have caused this? Should be taking the head off soon now. Thanks

 

[fjbj40]

All will be revealed once the head is off

 

[mbashier]

Round # 2 holding my breath…

 

[manofthewoods]

No compression and the valve stem is free to travel to the limits of the adjustment.
Worst case, the valve head is broken off and embedded into the top of the piston.
Best case, the seat in the head and on the valve head is burnt out to the point they don't touch anymore.

Either way, pics please.
View attachment 2772497
View attachment 2772498
View attachment 2772501

Flashback!
In ~1980 my HiLux dropped a valve.
It was "interesting"

 

[mbashier]

Well, I was expecting the worse and hoping for the best, and I think I got what I hoped for … exhaust valve cylinder #5

 

[mbashier]

Amazingly the cylinder wall seems to be in excellent condition as does the cylinder head, but can’t say for sure till I get it to the machine shop. There ain’t no ridge nor any scratches that I can feel with my fingernails.

 

[mbashier]

correct me if I’m wrong but the valve seems to have been physically chipped and not burned. This unexpected guest fell out of the head when I started fiddling with the broken valve and flipped the head. Could this be what caused the broken Valve? But I still haven’t figured why the valve stem maxes in height of the valve adjustment with no clearance. Possibly open the side cover and check the lifters?

 

[mbashier]

The problem valve compared to a new Japanese 3fe exhaust valve

 

[Rusty Marlin]

Not chipped, burnt. See the flow pattern that looks like water over sand? That's the hot gases cutting the steel at the grain boundaries.
As for the thumb nut, interesting piece. Not sure why it would be running loose in the head.

 

[mbashier]

Not chipped, burnt. See the flow pattern that looks like water over sand? That's the hot gases cutting the steel at the grain boundaries.
As for the thumb nut, interesting piece. Not sure why it would be running loose in the head.

Hats off to you sir, you really seem to know your thing. Is that nut even a part of the 3fe

 

[Rusty Marlin]

Hats off to you sir, you really seem to know your thing. Is that nut even a part of the 3fe

In my line of work, hot gas erosion is something we study and try to prevent; so I'm intimately familiar with its appearance, what causes it and how to delay it.