Crimson Yota

Hello everyone. I have a '90 3VZE with 230k miles. I did a compression test today and have a couple questions.

The Passenger side cylinder bank (#1 #3 #5) tested at ~150psi.

The Driver's side bank (#2 #4 #6) tested at ~120psi.

Does anyone have any insight on whether or not my head could be blown based on these numbers? Obviously if one cylinder was real low I would know it was no good, but the entire driver's side is lower than the passenger, but not obviously dead low..
Also to note, the driver's side cylinders were tested with the air intake disconnected to allow easier access the plugs, no idea if that would affect anything.

When starting it does produce white exhaust for a couple minutes, more than a normal car, but it's also been sitting for 8 years and it's cold out.. power isn't great driving around the neighborhood but isn't awful, but again, it's been sitting for 8 years and still had a few gallons of old gas in it when I put 5 fresh gallons in recently. No bubbles or residue in radiator, the oil cap has a couple flecks of milkshake color but otherwise pretty much clear, maybe a symptom of sitting? Maybe a blown HG? I'm not sure..

I would really appreciate it if someone gave me their thoughts.
I'm moving in a couple of weeks across country and if this truck requires a tear down it will have to go, but really don't want to part with it. Thank you in advance!

RJR

It does sound like the HG is suspect. If you really like the truck, why not just remove the rear drive shaft, put the front wheels on a dolly, and tow it to your new home? Then you can fix it after you get settled in.

Just another thought. Did you make sure the throttle was wide open when you ran the compression test? A closed throttle can lower the numbers somewhat.

COMTB

For comparison:

I ran a compression test on mine cold (hadn't been started in a few days) in below freezing temps and got 150+psi on all cylinders (one read around 160 psi). 270k 3VZE

To me it sounds like the HG might be on it's way out or leaking on the one side.

Crimson Yota

Thanks, guys!

It seems to be running okay right now, no overheating but haven't taken it on the highway. Would it be fine to drive it until there is actually an issue? Can a vehicle be okay as a daily with a slightly leaky HG, or is it toast?

I might be shipping it over to my new home, just curious if it would be okay to drive around on base with until I have the time and money to do the gaskets..

Last question: I'm not super expirienced when it comes to vehicles, me and my dad just replaced the timing belt, water pump, idler pulley, and fan bracket and it was all pretty straight forward. How much more complicated is it to remove the heads, if I'm extra careful with labeling and recording the tear down? Don't want to get in over my head.

Thanks again guys!

old87yota

Before saying the head gasket is bad, I would do a leak down test to see where the compression on the low bank is actually going.

I am not super familiar in how the 3VZ-E head gaskets tend to fail, but I think it is weird that all three would be the same low value due to a bad head gasket.

Are you 100% sure the timing belt was put on correctly?

Crimson Yota

Thanks for the reply.

No, not 100% sure when it comes to the belt.. could that cause lower compression in one bank?

old87yota

It could if the valves are not opening and closing when they should. Say if the crankshaft and one cam shaft were in time, but the other cam shaft was off time.

87-4runner

would probably make it overheat as well...

Crimson Yota

Thank you for the input guys!
Does anyone have any suggestions for what my next course of action should be?
Seems like it could be:

-Bad Head Gasket
-Timing is off
-Worn out engine/components?

Would a Combustion Leak Test Kit be a good next step to eliminate the HG from the equation? Or would a Leak Down test be better?
Or should I just say 'F-it for now' and drive it until it gives me a reason to tear it down again?

COMTB

So if the head gasket is going, you should be finding milkshake somewhere, I see you mentioned flakes initially but that could be condensation or moisture after not running. Has it gotten worse/better? Are you burning oil?

So I think your next step should be the leak-down mentioned. That should give you an idea if it's the rings being worn out or leaning more towards HG.

Does your exhaust smell sweet like cooking sugar? -- Coolant usually smells sweet coming out the exhaust

To verify your timing you could pull the cover and check the marks on the belts and pulleys. Make sure they are lined up correctly (the FSM has a good description of this). It is recommended to pull the plugs out if you're going to be manually cranking the engine over with a breaker to re-align the belt if it is miss-aligned.

If you don't over heat it and it's not going through oil/coolant at an alarming rate I don't see why it would be bad to drive it around but also I feel like that's asking for trouble knowing something could be wrong

old87yota

General statement:

Head gaskets can fail in all kinds of ways. They don't necessarily mean oil and coolant have to mix, or even a compression leak. Remember, head gaskets seal the combustion chambers, oil passages, and coolant passages from each other and to the atmosphere. This means that there are several potential ways for failure.


Back to the described problem:

You can do both a cooling system combustion leak test and a leak down test, but if you are not noticing the coolant level going down or excessive pressure in the cooling system, I think a leak down test will tell you more.

At this point, we are only guessing that the engine has a bad head gasket, but we have not proven that to be so.

The main reason I am hesitant to call it a bad head gasket is that it would be very unusual for all three cylinders to have a head gasket compression leak that would exactly match each other. I am not saying that it is not possible, but it certainly isn't common.

I would double check the mechanical timing of the engine and make sure the timing is correct. You want to look for the timing marks on the sprockets to all align to the timing marks in the cover when the engine is rotated to TDC #1. The marks on the belt itself probably won't line up just to the way the belt path is designed. It this the cam and crank sprocket marks that are important.

Then if the mechanical timing checked out fine, then do a leak down test to see where the compression is going.

ksti

RJR brings up a valid question.

old87yota

Yes, very good question.

You will want to have the compression test done with the throttle all the way open for all cylinders, so we get comparable compression numbers.

Was the throttle open for all tests?

Here is the factory procedure for reference.