YM226D Project

[CoyPatton]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

 

[bmaverick]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

Would you also recommend taking the radiator cap off or the overflow cap to see if bubbles start happening like a fish aquarium ? It may show if the head has issues, thus needing a new head gasket or other re-work.

I like your method of detection very much.

 

[tc197]

Personally I like using a leak down test to attempt to determine where my issue is at.
Simplified—you use compressed air to simulate compression, then check to see where the loss is going.
1 & 2) air hissing in exhaust or intake (1
& 2) loss points
3) Air hissing from oil pan (dip stick tube)
4) bubbles in coolant
5) air hissing from around valves with cover off
6) air hissing from oil passages

These give you a very good ideal of what is worn the worse in the engine.
Also bore scopes have gotten fairly inexpensive and can give good info before a tear down begins and reduces those OH CRAP! moments when you pull the head.

Thanks CoyPatton, that process makes a lot of sense. Mind helping me clarify a couple of details?

1. What PSI should I be using for testing purposes? Will 50psi get it done? 100? Just need to determine if I have to borrow a big compressor or if I can make do with what I have.

2. Can I use my compression injector adapter that I purchased from Hoye to connect to the compressor instead of the compression gage?

3. Any recommendations on a borescope? I've used one at work in the past but it was a high end laboratory grade unit with articulation. Does the harbor freight 75$ unit seem reasonable or is there something with a bit more bang for the buck out there?

Edit: It just popped into my head that the autoparts stores may loan these borescopes out and it looks like they do. I may try that option before purchasing.

Edit 2: Autozone had a borescope as part of their loaner program. Went and picked it up this morning. As long as I return it within 90 days they don't charge anything - can't beat that!

 

[CoyPatton]

Would you also recommend taking the radiator cap off or the overflow cap to see if bubbles start happening like a fish aquarium ? It may show if the head has issues, thus needing a new head gasket or other re-work.

I like your method of detection very much.

Either should work assuming the cap holds good pressure, but I prefer the radiator cap.

 

[CoyPatton]

I have always had access to a compressor that generates 100+ psi so I don’t know about about 50 psi, low psi may not seep past the pressure building up to 250 compression test levels.
As for fittings, sorry not much help.
With a borescope, you may be able to tell your issue. A valve that is burnt, or doesn’t close, a burnt piston head, damaged cyl walls. I would check that out first.

 

[bmaverick]

I have always had access to a compressor that generates 100+ psi so I don’t know about about 50 psi, low psi may not seep past the pressure building up to 250 compression test levels.
As for fittings, sorry not much help.
With a borescope, you may be able to tell your issue. A valve that is burnt, or doesn’t close, a burnt piston head, damaged cyl walls. I would check that out first.

Most of the stand-up Porter-Cable compressors reach 125psi and can do this compression leak down.

 

[CoyPatton]

Most of the stand-up Porter-Cable compressors reach 125psi and can do this compression leak down.

I think a 30 gal tank with a 100+ psi capability is about as small as I have ever used. It was a upright roll-around compressor with an oilless unit on it that a buddy owned that I used at his place. It worked, but I don’t know specifics about it at this point. Wild guess on tank size and psi, although 100psi capability is fairly common.
One think I can assure you of, is a slightly opened valve can deplete a 60 gal tank quickly.
The pressurization process of compression is very different than the pressure of a leak down test so there is not a need to match the psi for the leak down test, I just don’t know about 50psi forcing past weak seal points that still hold 250psi in a 450psi+ design cylinder.

 

[tc197]

Unsuccessfully tried to use the borescope today. I realized pretty quick when trying to insert it down the injector hole that the pre-combustion chamber is still in place. The borescope is much too big to fit through any of the holes in the chambers and the chambers seems to be pretty well stuck in there. Searching online it seems most people take the head off and knock them out from the back. I'm leaning closer to just pulling the head and diving in, but I'll do some more searching first.

 

[tc197]

Im doing some research on compression and leak tests. Im having trouble coming up with the connectors and adapters required to connect a compressor to the injector adapter - but in my searches I found people discussing wet vs dry compression tests.

Dry compression testing is what I already did. A wet compression test is done by adding a small amount of oil into the cylinder on top of the piston before checking compression. The results of the wet test, in theory, can help point to the source of the problem. If compression is higher in the wet test, chances are the rings are not sealing well and may need to be replaced. If compression doesn’t change, it points to valves or head gasket.

Any thoughts on me attempting a wet compression test to try and further diagnose the issue? I think its a step in the right direction in case I can’t get a leak down test put together.

 

[bmaverick]

Im doing some research on compression and leak tests. Im having trouble coming up with the connectors and adapters required to connect a compressor to the injector adapter - but in my searches I found people discussing wet vs dry compression tests.

Dry compression testing is what I already did. A wet compression test is done by adding a small amount of oil into the cylinder on top of the piston before checking compression. The results of the wet test, in theory, can help point to the source of the problem. If compression is higher in the wet test, chances are the rings are not sealing well and may need to be replaced. If compression doesn’t change, it points to valves or head gasket.

Any thoughts on me attempting a wet compression test to try and further diagnose the issue? I think its a step in the right direction in case I can’t get a leak down test put together.

What grade oil? 15W40 that is thick or SAE 30 being a tad thinner? 5W30 may be useless to test with wet.