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Could bad Glow plugs give low compression
- Thread starter Nowaydude
- Start date
JMJNet
Recruit
I am sure if you go to a hydraulic/racing shop, they can make anything you specified.
Ok, number 4 cylinder has only 160 psi, argh. Doing a leakdown test on it sounds like the air is comoling out of the exhaust. Could carbon be built up on the valve? I was trying to get the exhaust manifold off, can't seem to get the manifold nuts off, they just want to round off, already damaged Pryor. Any tricks or Idea's how to get them off???I tryed a nut splitter, didn't work, lol it flattened the cutter.air chisel maybe.maybe torch, or cut them off. Can the studs be replaced? Any Ideas, I'm sure someone has had this trouble before. Thanks. Mike
Will L.
Well-Known Member
For rounded of nuts, bolts, etc. Hands down, the very best option is Mac Tools Edge sockets. I know, sounds scary pricey, but these are the Taiwan made mac sockets and hold up amazingly well for the price. Should be around $160 for the set -SXDGM146BR
They will grab very rounded off fasteners. They will become your go-to set.
Once the intake manifold is off, do the spray bottle of water while running engine at 2,000 rpm to blast out the carbon. I think there is YouTube videos on how to. Doing it with manifold off so you can do 1 cylinder at a time is best in this situation imo.
While this will clear the carbon, it does not mean it will improve the compression. If carbon is allowing bleed off of that much, I cant imagine the piston didn’t already hit the valve.
Also if there is a severely cracked valve and carbon is plugging part of the crack, it could bleed more. Highly unlikely though.
Getting rid of the carbon is worth a shot because worse case scenario is the engine comes apart and instead of scraping by hand and brass wire wheel, the water will remove almost if not all. Your neighbors will hate you while doing it... If you have a soot trap inplace, might remove it for that part.
They will grab very rounded off fasteners. They will become your go-to set.
Once the intake manifold is off, do the spray bottle of water while running engine at 2,000 rpm to blast out the carbon. I think there is YouTube videos on how to. Doing it with manifold off so you can do 1 cylinder at a time is best in this situation imo.
While this will clear the carbon, it does not mean it will improve the compression. If carbon is allowing bleed off of that much, I cant imagine the piston didn’t already hit the valve.
Also if there is a severely cracked valve and carbon is plugging part of the crack, it could bleed more. Highly unlikely though.
Getting rid of the carbon is worth a shot because worse case scenario is the engine comes apart and instead of scraping by hand and brass wire wheel, the water will remove almost if not all. Your neighbors will hate you while doing it... If you have a soot trap inplace, might remove it for that part.
MrMarty51
Well-Known Member
Get some top end carbon removal chemical, Seafoam works good. run the engine at a fairly fast clip, 2000 rpm or so and pour some of that through the intake and see how it acts then.
Husker6.5
135' diagonal 16:9HD, 25KW sound!
Which cylinder had the bad lifter, and was it intake or exhaust? If the motor had one lifter hanging up, it's possible it has another one, but those are roller lifters and they just don't fail like that, especially at as low of mileage as you say is on the motor, unless it was ran with either really low oil (like down 3-4 quarts) or with really dirty oil. Also, if you hear air escaping from the exhaust when doing the leak down test, odds are it's a bent valve/valve stem from a collision with a piston, not carbon build up.
Hi: Thanks for the reply, air is leaking from number 4 cylinder exhaust during leakdown test, the bad lifter was number 6, intake, it collapsed pryor to me owning it, so I never heard it run, number 4 cylinder has 160 psi the rest are close to 400psi. I have to pull the head to find out why its leaking. I was thinking that maybe it idled alot and built up carbon since it was a plow truck, not on the highway. Just a thought. I was going to pull the exhaust manifold and try a scope to see the valve but didn't get that far yet. Manifold nuts are rusted and rounded. Can the manifold studs be replaced if I have to cut them to get it off? Thanks Mike
Will L.
Well-Known Member
Back in earlier post before the confusion of odd vs even side of engine- you said:
“#8-420, #6-475, #4-380, #2-360, i did this 2 times, to make sure readings were correct”
We now know those as 7,5,3,&1. And now cylinder 4 is at 160 psi but the other 3 are 400 psi ?!!!?
Yer done. Flip a coin and run as is till she pukes or remove and rebuild engine.
Iirc something about 60-70k miles on engine? Wasn’t rebuilt right then. You mentioned previous owner did hackery mechanical. That is the only thing that adds up here. Possible he simply lied about mileage when selling and you have another 100,000 + miles on there you don’t know about?
10% difference in any 2 cylinders is an issue. You way more than meet that qualification. Plan on complete rebuild imo.
“#8-420, #6-475, #4-380, #2-360, i did this 2 times, to make sure readings were correct”
We now know those as 7,5,3,&1. And now cylinder 4 is at 160 psi but the other 3 are 400 psi ?!!!?
Yer done. Flip a coin and run as is till she pukes or remove and rebuild engine.
Iirc something about 60-70k miles on engine? Wasn’t rebuilt right then. You mentioned previous owner did hackery mechanical. That is the only thing that adds up here. Possible he simply lied about mileage when selling and you have another 100,000 + miles on there you don’t know about?
10% difference in any 2 cylinders is an issue. You way more than meet that qualification. Plan on complete rebuild imo.
Yeah , your right, he probably lied about the milage, It smokes too much to run till it pukes, I'll probably pull the even side head and see why valve is leaking. Maybe the valve hit the piston and was bent, who knows. It did start and run pretty well except for the smoke. It wouldn't pass inspection this way. Are the cylinders sleeved for rebuilding? Thanks. Mike
Will L.
Well-Known Member
Cylinder walls are near perfect 90% of the time on these crazy engines. Rings usually get ruined first.
Really no air leaking into crankcase on leakdown? Wacky.
Valves hit pistons all the time. Timing chain gets stretched and people over rev. El-smako. It really is a stout engine to handle it, but they do. Cant count how many came in while guys were driving it and said-“yeah,been running weird and lower power for last 2,000 miles.” We put them in a different truck and pull it apart to see 2 pushrods trying to make letters “c” haha.
If you do re- ring it- examine for main web cracks before pulling crankshaft. If cracked and you don’t want to spend $$$, just pull the pistons with crankshaft in place. I’ve Done it more than once.
New rings, ball hone the cylinders, new rod bearings, new front & rear main seal, new ac delco balancer set.
Disturbing the cracked main webs and not welding or locknstictch fix will only make them crack out sooner.
New timing chain (gears not needed for a beater) and as little headwork as possible. New head bolts and quality head gaskets.
New rocker buttons and a tube of the right stuff from permatex. Only head gaskets, main seals needed. Dont bother with full gasket set.
That is- IF you dont get a junkyard injection line, smashed flat so no fuel goes through on the bad cylinder. Install for testing only- NEVER to cheat on a smog test. Remember:
EPA stands for Everyone’s Perfect Association, and we never cheat them.
Really no air leaking into crankcase on leakdown? Wacky.
Valves hit pistons all the time. Timing chain gets stretched and people over rev. El-smako. It really is a stout engine to handle it, but they do. Cant count how many came in while guys were driving it and said-“yeah,been running weird and lower power for last 2,000 miles.” We put them in a different truck and pull it apart to see 2 pushrods trying to make letters “c” haha.
If you do re- ring it- examine for main web cracks before pulling crankshaft. If cracked and you don’t want to spend $$$, just pull the pistons with crankshaft in place. I’ve Done it more than once.
New rings, ball hone the cylinders, new rod bearings, new front & rear main seal, new ac delco balancer set.
Disturbing the cracked main webs and not welding or locknstictch fix will only make them crack out sooner.
New timing chain (gears not needed for a beater) and as little headwork as possible. New head bolts and quality head gaskets.
New rocker buttons and a tube of the right stuff from permatex. Only head gaskets, main seals needed. Dont bother with full gasket set.
That is- IF you dont get a junkyard injection line, smashed flat so no fuel goes through on the bad cylinder. Install for testing only- NEVER to cheat on a smog test. Remember:
EPA stands for Everyone’s Perfect Association, and we never cheat them.
Will L.
Well-Known Member
Just be 100% no air loss past rings before yankin head(s).
From what I understand you have low compression on 3 cylinders- 2 on one side and one on the other. So if it’s going to be worth doing one head, do both. Only another 1-2 hours total, 1 more head gasket, one more set of head bolts- so like $35 in parts more. Be careful reading ny posts later when you get it apart- I am really bad about “while your there”
Then only if something major wrong that requires parts does the cost go way up.
You could do leak down test, then squirt oil in as if NOT ACTUALLY doing a wet compression test. Ensure no air loss to speak of past rings. Doing accurate testing before things come apart is super helpful on decisions later if something HAS to be done or if you can squeak by.
From what I understand you have low compression on 3 cylinders- 2 on one side and one on the other. So if it’s going to be worth doing one head, do both. Only another 1-2 hours total, 1 more head gasket, one more set of head bolts- so like $35 in parts more. Be careful reading ny posts later when you get it apart- I am really bad about “while your there”
Then only if something major wrong that requires parts does the cost go way up.
You could do leak down test, then squirt oil in as if NOT ACTUALLY doing a wet compression test. Ensure no air loss to speak of past rings. Doing accurate testing before things come apart is super helpful on decisions later if something HAS to be done or if you can squeak by.
Thanks, How much air pressure should I be using doing a leak down test, I was usung a bout 30 psi. Should i do a wet compression test on the low cylinders too to see if compression goes up, if not it's definitely the heads or gasket? Thanks. Mike
Would blocking off bad cylinder fuel line damage engine, running it like that?
Will L.
Well-Known Member
Wet compression test turns the oil you are using into fuel and the cylinder ignites blowing compression gauge up like hand grenade. You have to be able to do it with liquid that cant combust if doing wet comp test.
Otherwise, do leak down (100psi is how I learned it) dry and wet- very rarely you can tell the rings/walls are bad that way but worth trying if unsure.
Blocking off injection line and running engine is like unplugging spark plug wire and injector on a gas engine. It will fight the other cylinders and not just loose power from itself not working but make the other cylinders work harder. Your turning the v8 into v7 with power of v5. It is taking life out of the engine faster. Not a great long term option but sometimes ya do what ya gotta do. But if soon to be rebuilt/ replaced anyways...
Otherwise, do leak down (100psi is how I learned it) dry and wet- very rarely you can tell the rings/walls are bad that way but worth trying if unsure.
Blocking off injection line and running engine is like unplugging spark plug wire and injector on a gas engine. It will fight the other cylinders and not just loose power from itself not working but make the other cylinders work harder. Your turning the v8 into v7 with power of v5. It is taking life out of the engine faster. Not a great long term option but sometimes ya do what ya gotta do. But if soon to be rebuilt/ replaced anyways...