Dead cylinder in 1972 2002tii

[Pablo M]

Update.

Went to pick up the car and owner talked to me again, this time much nicer and explaining things more. 
 

Cylinder 2 is the dead one. On compression test all other cylinders had 160psi, +/- 5psi. No 2 had 5psi. Five. 
he said it could be a piston, rings, burnt valve, and given the condition of the rear of the car, the fact engine doesn’t look like it’s ever been apart, and the blue smoke he thought it next to stop there. No point in just fixing/replacing the head of the bottom end was also shot. That’s why he said it’s an engine rebuild that’s needed. He also didn’t charge me anything for all the diagnostics and PPI type inspection they did. So there’s that. 
 

If I can get it run in g on 4 cylinders that might be enough to enjoy the car, but the plugs are getting fouled with oil pretty quickly so the rings are probably shot too. I suppose what I’ll do is pull the motor, strip it down to a long block and have it rebuilt by another shop (that’s cheaper than him). 

[Son of Marty]

So with new plugs it does run on all 4 for a while? With those compression numbers it's hard to think you rings or valves are worn, maybe a broken oil ring in #2. I think my next step would be to borrow or buy a bore scope and check #2 for gouges on the cyl walls.

[tech71]

11 minutes ago, Pablo M said:

Cylinder 2 is the dead one. On compression test all other cylinders had 160psi, +/- 5psi. No 2 had 5psi. Five. 

For whatever reason, thats dead alright. Sorry

Dont skimp on the engine, cheaper shops are not always a good thing.

[Son of Marty]

Whoops I read that as #2 had the 160+5. Please disregard my last post👎. My Evelyn Woodhead sped read'n course is wearing off my cophention is in the dumper😲.

Edited August 14, 2023 by Son of Marty

[Pablo M]

24 minutes ago, Son of Marty said:

So with new plugs it does run on all 4 for a while? With those compression numbers it's hard to think you rings or valves are worn, maybe a broken oil ring in #2. I think my next step would be to borrow or buy a bore scope and check #2 for gouges on the cyl walls.

Doesnt run on #2 at all. You can pull the lead and idle doesnt change.  As I drive it more, the 25 miles from the shop back home, its getting slightly worse, I supposed from the plugs fouling. Dunno. But its minor change, noticeable though. I do plan to run a borescope in to see whats what, after I get back from Monterey car week.

 

17 minutes ago, tech71 said:

For whatever reason, thats dead alright. Sorry

Dont skimp on the engine, cheaper shops are not always a good thing.

Its cheaper shop, but not cheap, and well respected. Rebuilt a friends 2002 motor, a member here. Won't be cheap but wont be exorbitant like the current shop is.

[66Vette]

Holy cow !  There is much more you can do to diagnose this before you dive into a complete engine rebuild.  Very suspicious that three cylinders test so well and one is bad. 

 

Do a leak down test.  You inject air into the cylinder and essentially measure how big the leak is.  While you have the cylinder pressurized, listen to where the air is going.  If it is passing into the crankcase (you will be able to feel air passing out through the dipstick or valve cover breather), this suggests ring seal.  Put a shot of oil into the cylinder and repeat the leak down, if the numbers improve, it further points to ring seal.

 

A next possible source is the exhaust valve.  With the cylinder pressurized, listen for leaks out the exhaust.  I have been able to hear the leak all the way at the tail pipe.  The intake valve is rarely a culprit, but you'll hear air coming out your intake is this is the source.

 

 

 

 

[jimk]

With 3 cyl good compression, I vote for a burned valve.

 

If the bottom end was shot, how the good compression on 3 cyl?

 

Check the valve lash, I'm thinking they are tight.

 

Pull the head and look.  No need to spend crazy money from the get go.

Edited August 15, 2023 by jimk

[Rob Zaeos]

Hey Pablo, I have a bore scope. We could pop it in there and see what’s what. Hit me up on instagram.

[tech71]

17 hours ago, jimk said:

Pull the head and look.  No need to spend crazy money from the get go.

Or just set up a leak down test, while #2 is pressurized stick your ear up to your tail pipe, hear a hiss? Probably a bad exhaust valve.

Hissing from carb = intake valve

Hissing from oil filler or dipstick tube = rings

Probably😉

Edited August 15, 2023 by tech71

[jimk]

18 minutes ago, tech71 said:

Or just set up a leak down test,

At 5 psi on compression test, no need.

[OldRoller]

6 minutes ago, jimk said:

At 5 psi on compression test, no need.

Yep, time for the head to come off....

[66Vette]

A compression test will tell you nothing more than you have a bad cylinder.  A leak down can tell you WHY you have a bad cylinder.....

[Son of Marty]

As agent 66 said a leak down will pin point the problem whatever it is but you'll still need to pull the head to repair which kinda renders the leak down redundant.

[TobyB]

Whut?

 

Yes, compressed air into the victim.  If you're stupid lucky, you have a valve so out of adjustment it's not closing.

 

If you're average lucky, you have a burnt exhaust valve.

 

If you're stupid unlucky, you have a hole in a piston.   But 5 minutes with compressed air into #2 with it at tdc

and you'll know.  No need to get fantsy- just unscrew the end of a compression tester, take the valve out of it,

and run a few psi in there.

 

I'd say it's almost impossible that it's rings at this point- but that would also be stupid unlucky, Because the rings 

would have gouged the Snake River Canyon into the block for THAT much leakage, and they just don't do that.

 

Then, off with its head, unless you're REALLY lucky and loosening the valve (and driving it a hundred or 2 miles 

to let it reseat) gets everything back.

 

But it's all up to you at this point- we're just cheerleaders and politicians, here.

 

t

 

[Pablo M]

On 8/14/2023 at 6:52 PM, Rob Zaeos said:

Hey Pablo, I have a bore scope. We could pop it in there and see what’s what. Hit me up on instagram.

Quick update. Rob came by and we took a look inside #2. Nothing looked outwardly bad. Cylinder walls looked normal, no sign of gouges or anything on the cylinder walls. Top of piston looked fine as well. Valves looked ok, but tons of carbon buildup on the head and valves.

 

Next we're going to adjust valves to make sure they're all closing as they should, then run another compression test to baseline, and another compression test after putting some oil down in the cylinder to see if that changes the compression readings.

 

I don't have the facilities/tools to do a leak down test. I may pull the head next to get a good look at whats going on.