What to do with leak down and compression test results (1 Viewer)

[rosi6655]

Hey fellas.

I have a 1996 LX450 and I noticed a had to add a tiny bit of coolant over the past 1000 miles. I couldn't find any leaking hoses, and as far as I can tell it has been running fine. I performed a leak down test on each cylinder followed by a compression test. I did the leak down test at 75 psi. Here are the results of that:

C#1 72 psi - radiator level rising/few bubbles, air coming out of oil fill cap
C#2 70 psi - air coming out of oil fill cap
C#3 56 psi - air coming out of oil fill cap
C#4 66 psi - air coming out of oil fill cap
C#5 68 psi - air coming out of oil fill cap
C#6 70 psi - radiator level rising/ few bubbles, air coming out of oil fill cap

During this test I didn't hear any air leaking through the exhaust or intake.

Results of compression test:

C#1 - 190 psi
C#2 - 180 psi
C#3 - 120 psi
C#4 - 185 psi
C#5 - 155 psi
C#6 - 180 psi

These results for sure tell me that I have a small head gasket leak although I have had no coolant in the oil or vice versa. The leak down and compression tests are marginal/bad on a couple of cylinders.

I am not a seasoned mechanic by any stretch, but this is looking like the entire engine needs work. I am looking for any advice and guidance you all may have on the next steps and the best path forward. It is worth noting, I love this truck and I have not noticed any degradation in performance.

 

[leonard_nemoy]

Combustion gas test?

 

[rosi6655]

Combustion gas test?

Negative. I figured if I was getting air in the radiator at 75 psi, the head gasket was compromised.

 

[Kernal]

An engine oil analysis might be interesting??

 

[rosi6655]

An engine oil analysis might be interesting??

I can look into getting an oil analysis done and doing a combustion gas test. From what I understand of the leak down test results though, air pressure cannot get into the radiator without a leaking head gasket. I also know that I am losing coolant somewhere.

What would the results of an oil analysis and combustion gas test tell me in addition to what I learned from the initial tests?

 

[leonard_nemoy]

I can look into getting an oil analysis done and doing a combustion gas test. From what I understand of the leak down test results though, air pressure cannot get into the radiator without a leaking head gasket. I also know that I am losing coolant somewhere.

What would the results of an oil analysis and combustion gas test tell me in addition to what I learned from the initial tests?

Really nothing other than confirm the head gasket.

 

[BILT4ME]

I can look into getting an oil analysis done and doing a combustion gas test. From what I understand of the leak down test results though, air pressure cannot get into the radiator without a leaking head gasket. I also know that I am losing coolant somewhere.

What would the results of an oil analysis and combustion gas test tell me in addition to what I learned from the initial tests?

Oil analysis will tell you if there is any contamination in the oil of antifreeze or severe wear that's taking place.

The combustion gases test will confirm if there are actually hydrocarbons going into the radiator during engine operation and combustion.

Both will confirm a HG issue.

A leakdown test coming out the oil fill cap is normal Air will absolutely leak past the rings due to standard ring gap. If there was nothing out the intake or exhaust it tells you that your valves are sealing. Depending on the AMOUNT of air coming out of the rings, will determine if the rings are severely worn or just normal design leakage.

 

[rosi6655]

Oil analysis will tell you if there is any contamination in the oil of antifreeze or severe wear that's taking place.

The combustion gases test will confirm if there are actually hydrocarbons going into the radiator during engine operation and combustion.

Both will confirm a HG issue.

A leakdown test coming out the oil fill cap is normal Air will absolutely leak past the rings due to standard ring gap. If there was nothing out the intake or exhaust it tells you that your valves are sealing. Depending on the AMOUNT of air coming out of the rings, will determine if the rings are severely worn or just normal design leakage.

That all makes sense. The compression test and leakdown test are certainly telling me there is some sort of issue with cylinder 3. So you all would do additional testing before you start tearing into the engine?

Is there any risk of causing additional damage to the engine if I continue to drive under these conditions? I started this because I was searching for missing coolant, not because I noticed any big change in performance.

 

[BILT4ME]

That all makes sense. The compression test and leakdown test are certainly telling me there is some sort of issue with cylinder 3. So you all would do additional testing before you start tearing into the engine?

Is there any risk of causing additional damage to the engine if I continue to drive under these conditions? I started this because I was searching for missing coolant, not because I noticed any big change in performance.

I would keep driving until I had confirmation of the issue.

A small HG leak will not cause further damage until it gives out and then is a huge smoker. Don't stray too far from home, once it blows smoke, don't drive it anymore, but definitely don't let it sit with coolant in a cylinder. and don't run it if you get milkshake oil. That will kill the lower end in a heartbeat.

It took me nearly 2 years to find a coolant leak on mine that ended up being the coolant bypass pipe on the R side of the engine with 3 O-Rings.

Once I got those fixed, my cooling system pressures came up again and then the radiator started leaking. Now I need to replace that again.

Make sure you check all avenues.

Someone may chime in and tell you to do a cooling system pressure test. If you do, you may push coolant into a cylinder and if so, you could hydraulic a cylinder if you do not pull the spark plugs after that test, and before you try to start it.
At least if it is from a cylinder, then the pressure from combustion will push the coolant out of the cylinder until it's a catastrophic failure.


That said, it can do more damage if it decides to get bad when you shut it off, then it blows coolant into the cylinder. if, at ANY time, your engine tries to turn over but doesn't, DON'T keep trying, as you may bend a rod or a crank while trying to push the liquid out of the cylinder with no place to go.

 

[rosi6655]

I would keep driving until I had confirmation of the issue.

A small HG leak will not cause further damage until it gives out and then is a huge smoker. Don't stray too far from home, once it blows smoke, don't drive it anymore, but definitely don't let it sit with coolant in a cylinder. and don't run it if you get milkshake oil. That will kill the lower end in a heartbeat.

It took me nearly 2 years to find a coolant leak on mine that ended up being the coolant bypass pipe on the R side of the engine with 3 O-Rings.

Once I got those fixed, my cooling system pressures came up again and then the radiator started leaking. Now I need to replace that again.

Make sure you check all avenues.

Someone may chime in and tell you to do a cooling system pressure test. If you do, you may push coolant into a cylinder and if so, you could hydraulic a cylinder if you do not pull the spark plugs after that test, and before you try to start it.
At least if it is from a cylinder, then the pressure from combustion will push the coolant out of the cylinder until it's a catastrophic failure.


That said, it can do more damage if it decides to get bad when you shut it off, then it blows coolant into the cylinder. if, at ANY time, your engine tries to turn over but doesn't, DON'T keep trying, as you may bend a rod or a crank while trying to push the liquid out of the cylinder with no place to go.

I am glad you mentioned that. Pushing coolant into a cylinder is not something I had considered.

I will continue to drive for a while and monitor symptoms. The truck needs attention for sure in other areas, but I wanted to gauge the general engine health before I handed my wallet over to the parts store. I am not sure what to make of the bad compression on cylinder 3. If it keeps getting worse I guess I will start to get a misfire.

The truck is due for an oil change soon anyways. Where do you recommend getting an oil analysis done?

I really appreciate all of the feedback you all have given.

 

[zapatius]

I am glad you mentioned that. Pushing coolant into a cylinder is not something I had considered.

I will continue to drive for a while and monitor symptoms. The truck needs attention for sure in other areas, but I wanted to gauge the general engine health before I handed my wallet over to the parts store. I am not sure what to make of the bad compression on cylinder 3. If it keeps getting worse I guess I will start to get a misfire.

The truck is due for an oil change soon anyways. Where do you recommend getting an oil analysis done?

I really appreciate all of the feedback you all have given.

Blackstone for oil analysis

 

[Comet]

Blackstone Labs. Mentioned a lot on MUD. Analysis also shows other metals/wear items.

 

[rosi6655]

Blackstone Labs. Mentioned a lot on MUD. Analysis also shows other metals/wear items.

Right on. I will order a kit. Hopefully I get nothing but good news.

 

[BILT4ME]

Blackstone will send you free sample bottles and will email you an analysis report

You can read other folks' reports on here:

Post Your Blackstone Report

Post your Blackstone Oil Sample report so others can see what to look for and what issues may come up. This is my 4th oil report on my 96 Land Cruiser 1FZ-FE. Looks like I'm seeing some sudden wear. I need to address this with a fresh air filter, as I have had NO work done on this engine and...

forum.ih8mud.com

Blackstone Labs

 

[rosi6655]

Does anyone have an idea at what compression levels start to cause a misfire on a cylinder? If I recall correctly, the FSM specs 179 psi as a minimum, and my cylinder #3 is at 120 psi. If that gets much lower and starts to misfire then I will need to look into a bottom end rebuild right?

Does anyone have any experience with what could cause more compression loss on one cylinder than the others? Could it just be a bad ring that has worn worse than the others?

 

[BILT4ME]

Does anyone have an idea at what compression levels start to cause a misfire on a cylinder? If I recall correctly, the FSM specs 179 psi as a minimum, and my cylinder #3 is at 120 psi. If that gets much lower and starts to misfire then I will need to look into a bottom end rebuild right?

Does anyone have any experience with what could cause more compression loss on one cylinder than the others? Could it just be a bad ring that has worn worse than the others?

Lack of compression won't cause a misfire. unless there is virtually no compression (hole in piston)

Lack of an explosion allows it to read a misfire (via the knock sensors and resistance to the spark plug leads) so a lack of fuel, lack of spark, or coolant in the cylinder will cause a misfire.

Lack of compression on ONE cylinder can be a worn ring, broken ring, a scored cylinder wall, a cracked cylinder wall, a bad HG, a cracked head, hole in a piston.....

 

[rosi6655]

Lack of compression won't cause a misfire. unless there is virtually no compression (hole in piston)

Lack of an explosion allows it to read a misfire (via the knock sensors and resistance to the spark plug leads) so a lack of fuel, lack of spark, or coolant in the cylinder will cause a misfire.

Lack of compression on ONE cylinder can be a worn ring, broken ring, a scored cylinder wall, a cracked cylinder wall, a bad HG, a cracked head, hole in a piston.....

I will continue to drive for a while and monitor symptoms. I will wait to see what the oil analysis has to say.

 

[jpoole]

How did the spark plugs look when you pulled them for the tests? If you have relevant levels of coolant going into a cylinder that plug will be steam cleaned. You could have a very minor leak without this effect but once there's enough coolant going into the cylinder this should be evident when you pull the plugs.

 

[rosi6655]

How did the spark plugs look when you pulled them for the tests? If you have relevant levels of coolant going into a cylinder that plug will be steam cleaned. You could have a very minor leak without this effect but once there's enough coolant going into the cylinder this should be evident when you pull the plugs.

All of the plugs had some scaling on them (does that suggest anything in particular?). No noticeable difference between cylinders. I had never taken the plugs out before, so I have no idea how many miles were on them. I gapped all of the old plugs and they were all over the 0.031" spec from the FSM by about 0.010" A couple of them were a lot looser than I was expecting and I found some oil and the spark plug wells, so I guess my valve cover gasket is starting to go as well.

I have changed the plugs and I will take a look at them again after a run through a couple of tanks of gas.

 

[BILT4ME]

All of the plugs had some scaling on them (does that suggest anything in particular?). No noticeable difference between cylinders. I had never taken the plugs out before, so I have no idea how many miles were on them. I gapped all of the old plugs and they were all over the 0.031" spec from the FSM by about 0.010" A couple of them were a lot looser than I was expecting and I found some oil and the spark plug wells, so I guess my valve cover gasket is starting to go as well.

I have changed the plugs and I will take a look at them again after a run through a couple of tanks of gas.

If you still have the old plugs and know what order they were in, post pics of the tips and we can give you an armchair diagnosis.