Do I have a blown head gasket based off these compression readings?

[4flyer]

Let's play "how screwed am I?"

Over the past 6 months, I have noticed that I sometimes have a misfire on startup that goes away when things warm up. Started to get concerned but the 4runner is no longer my daily so did not make diagnosis a priority. Started getting a P0300 code. Months later, a P0303 accompanied it. If I let the engine sit for a few days, I'd get smoke from the exhaust. 4Runner needs work and the valve cover gasket needs replacement.

Decided to do a compression test. Got a tester from oreilly's.
Compression test was done cold.

Cylinder 1: 210
Cylinder 2: 195
Cylinder 3: 180 <---
Cylinder 4: 210
Cylinder 5: 208
Cylinder 6: 210

Tried it again on 3 and got the same results.

Added some oil to #3. Compression shot up to 250. Worn piston rings?

I also think I screwed up reassembly. Now getting a flashing engine light with P0300, P0303, P0304, P0305, and P0306. I assume I put some wires out of order? Also has terrible misfire now. Exhaust very smoky but I assume that is the oil from cylinder 3 burning off.

What is the prognosis? Head gasket?

Thanks!

 

[2TH4IST]

I'd say I'd be suspicious of cylinder 3. Have you done a leakdown test yet? That will tell you if it's top end (head) or bottom end (rings), or a cracked head (pressure in cooling system on cold engine).

Had similar issue on my miata, but I burnt up cylinder 4 valves at 80% leakdown. Miss when cold, went away when warmed up. Drove it this way for years, until it started loosing power. Did a compression test, got bad results but gave me a direction. Leak down told me what was wrong.

You can also use that blown headgasket tester with the blue fluid. Turns yellow for a blown hg.

Also if you squirt to much oil in there it will bump up the compression.

 

[brillo_76]

My signature has the link to the spark plug wiring. You can use that diagram to verify your spark plug wires.

Extremely rare to have warn rings but can happen. Also a borescope camera down the spark plug hole will show you what
the Cylinder walls look like on cylinder 3

 

[4flyer]

I'd say I'd be suspicious of cylinder 3. Have you done a leakdown test yet? That will tell you if it's top end (head) or bottom end (rings), or a cracked head (pressure in cooling system on cold engine).

Had similar issue on my miata, but I burnt up cylinder 4 valves at 80% leakdown. Miss when cold, went away when warmed up. Drove it this way for years, until it started loosing power. Did a compression test, got bad results but gave me a direction. Leak down told me what was wrong.

You can also use that blown headgasket tester with the blue fluid. Turns yellow for a blown hg.

Also if you squirt to much oil in there it will bump up the compression.

Thanks! I plan on doing a repeat of the tests this week after fixing the spark issue. I also plan on doing a leak down test.

I moved the 4runner this morning. Only ran it for about a minute. I checked the radiator cap after and when I removed the cap, coolant came pouring out like it was pressurized. Does this point to cracked head?

 

[brillo_76]

Thanks! I plan on doing a repeat of the tests this week after fixing the spark issue. I also plan on doing a leak down test.

I moved the 4runner this morning. Only ran it for about a minute. I checked the radiator cap after and when I removed the cap, coolant came pouring out like it was pressurized. Does this point to cracked head?

The coolant system is pressured roughly 13 to 16 psi I believe. You have to leave the cap completely off from cold for it not to have any pressure build up.

Was there bubbles in it?

 

[Hungryhawk]

My only experience with blown headgasket was a GM V8 aluminum block with known head bolt issues. Traded it in ,as it was, on a new Ford.
Your problem seems milder and you can still drive it. Checking for oil in coolant and the dissolved exhaust gas test is easy and informative. Also look for coolant in oil. My GM engine showed both.
Another possibility is a stuck top piston ring?
Perhaps try soaking that cylinder a couple days by putting a carbon dissolving product into cylinder thru spark plug hole. I am thinking Seafoam or similar. I would have piston mostly down to keep chemicals away from head gasket.
Then vacuum it out, flush with some engine oil, vacuum it out. Reinstall plug and drive.
I would try to minimize additives & oil left in cylinder to protect your cat converter.

 

[SaulG]

What did cylinder 3 spark plug look like? Leak usually steam cleans cylinder, plug, valves. Might be small leak overnight (no cyl pressure).
That clears once running.

 

[4flyer]

What did cylinder 3 spark plug look like? Leak usually steam cleans cylinder, plug, valves. Might be small leak overnight (no cyl pressure).
That clears once running.

The cyl 3 plug looked like the others: dirty and neglected lol. It was not clean

 

[Twisted Sid]

Try using one of these testers

https://a.co/d/9Rulrms

 

[nissanh]

While engine is running and radiator cap is on, check any bubbling in the reservoir.

 

[phattyduck]

If I let the engine sit for a few days, I'd get smoke from the exhaust.

Decided to do a compression test. Got a tester from oreilly's.
Compression test was done cold.

Cylinder 1: 210
Cylinder 2: 195
Cylinder 3: 180 <---
Cylinder 4: 210
Cylinder 5: 208
Cylinder 6: 210

Tried it again on 3 and got the same results.

Added some oil to #3. Compression shot up to 250. Worn piston rings?

What *KIND* of smoke out the exhaust? Coolant burning has a distinct sickly sweet smell (of coolant)... if it doesn't smell like coolant, it isn't burning much coolant. You might have a weak fuel injector or some other issue, or it could be a little oil leaking down into the cylinders when off.

180psi cold isn't scary, but it is low compared to the others (but the 195 cylinder is halfway 'down' from the good cylinders, so?).

I would still suspect something 'outside' the engine still. What year? What mileage? Any maintenance history?

-Charlie

 

[mtbtim]

Just do a leak down test of the #3 cylinder and get a more definitive answer of where you're losing the compression to. If you're losing it to the cooling system, it could either be a crack in the head or a head gasket issue, but most likely a cracked head. If you're losing it to the crankcase, it could be getting past the rings or via the head gasket between the combustion chamber and an oil gallery. It could be going out via either an exhaust or intake valve which could be fixed with a valve adjustment or maybe not if the valve is partially burnt. Finally, it could be going out via a neighboring cylinder if the head gasket failed between the cylinders.

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If you do suspect you are losing the compression into the cooling system, you can use a leak down tester in conjunction with a cooling system pressure tester to help diagnose the issue.


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[BuffaloBass]

PS my head gasket leak caused " lean condition" codes before it started steaming out the exhaust pipe.

We usually looked for 10% error or less. I would check cooling system pressure next. Not clear your head gasket is gone.

 

[St Runner]

Spark plug was dirty and when oil was added the compression went up to 250. That points towards the rings not sealing. Oil should not affect the valves or head gasket

 

[phattyduck]

Spark plug was dirty and when oil was added the compression went up to 250. That points towards the rings not sealing. Oil should not affect the valves or head gasket

It also sounds like way too much oil was added... :biggrin1:

-Charlie

 

[mtbtim]

It also sounds like way too much oil was added... :biggrin1:

-Charlie

I was thinking the same thing. He's lucky he didn't hydrolock his engine. At top dead center, the area left between the piston and the valves is pretty small.

 

[BuffaloBass]

I actually think oil will compress some, water WILL NOT! Again,, the cylinder PSI are within 10% of each other, i would look elsewhere.

NEXT STEP: Pressure test the cooling system to 20psi and see if it holds pressure. Auto parts store may have a pressure testor to let out. If it leaks down, then you have found a coolant leak.

 

[AuSeeker]

I actually think oil will compress some, water WILL NOT! Again,, the cylinder PSI are within 10% of each other, i would look elsewhere.

NEXT STEP: Pressure test the cooling system to 20psi and see if it holds pressure. Auto parts store may have a pressure testor to let out. If it leaks down, then you have found a coolant leak.

Oil nor any liquid for that matter will compress!

 

[phattyduck]

I actually think oil will compress some, water WILL NOT! Again,, the cylinder PSI are within 10% of each other, i would look elsewhere.

While oil is generally *slightly* more compressible than water, they are both generally considered incompressible when it comes to things like this. In fact, your engine relies on this - that's how the oil film works around the bearings in your engine's rotating assembly. If it was compressible, you would have metal-to-metal contact all over your engine and it wouldn't last very long.

-Charlie

 

[Previologist]

By what math is 180 within 10% of 210?