2G Diagnosing a possible bent valve without removing the head

[roadtrip_69]

All,

13 yr owner, and on my last leg of sanity. Getting to be more diagnosing and fixing than driving/upgrading the last couple years.

Scenario - Just built the bottom end almost exactly one year ago. All manley forged parts. After a few hiccups after putting it all back together has been generally running great, lots of power and no obvious issues, aside from a small leak from the oil pump seal, which has been that way since the build. (bad seal apparently with the new oil pump)

Started having getting too hot issues especially when running the a/c about 2 or 3 weeks ago, once it started getting into the 90's. ( Yes i know, wow i still had a/c but its also basically a over built daily driver) it was getting hot enough for the ECU to tell the A/c to turn off, especially at stop lights. Which from what I read is 236 degrees but not much hotter than that.

I had a stock cap, stock radiator and mishimoto slim line fans kit. Determined my cap was definitely wore and leaking, got a new one, higher pressure from mishimoto, and decided to go ahead and get their upgraded radiator too, and a 170 degree thermostat. Cause you know last thing i want is a warped head gasket. After all the time and money spent rebuilding the bottom end a year ago. Also decided to put my stock fans back on, not as pretty and some clearance issues but I hear they work a lot better.

Also did a flush. The temps definitely showed improvement. But then the irony, one of my heater hoses started leaking, but i thought it was the caps over flow hose cause i forgot to tighten down the clamp all the way.. the simple things...
But determined about 3 or 4 miles later when i stopped at a gas station and was filling back up the coolant, that the leak was much bigger and from my upper heater hose.
I called in reinforcements to help me go get one and put it on where I was.
Started the car up after again refilling the coolant, started right up, but there was definitely a vacuum issue, instead of the normal negative 19-20 in/hg/psi? it was only keeping about 15. Drove it home though without much issue, never really got hot till i got home, and parked it.
Discovered that the hose i just replaced, the clamp wasn't sealing quite enough, and it was venting steam and a small amount of fluid into the passenger compartment. Fixed that with a new clamp in the AM.

Started it up, fired up fine, but again vacuum was even a little less than the day before about 10-15 and bouncing, not steady, sounded rough. Drove it around the block, it wouldn't boost very well, definitely lacked power.

Parked it, figured worst case, a head gasket, did a compression test got 177, 165,165, 176 going 1, 2, 3,4 cylinders. Hits both criteria according to the book on being within spec.. though on the outside edge. (178 psi standard, 133 psi minimum. With 14 psi max difference between cylinders.)(plus i never did a compression test after the build I dont actually know what compression was when freshly built, sadly). I got tired of working on it. Let it sit for the night.

Tried to start it back up the next day to start eliminating things. Car wouldn't start at all. Cranked fine but would not fire over. Replaced the ignition module with a spare, the cam sensor with a spare, no change. Checked fuel and spark, was getting fuel but absolutely no spark. Figured for NO spark it had to be the ecu or crank. So I put in a spare ecu, no change at all. Leaving just the crank sensor.

Did the fun fun job of tearing down all the belts, the covers, the motor mount etc. To discover timing was off. Belt was fine, but timing was off at least 3-4 teeth. No Idea how, other than tensioner issues? (cams were in time with each other but the crank was not in time with the cams) None the less, put it back in time.

It started right up but again was idling around 10 -12 on vacuum..again. And bouncing and just sounding bad may or may not have had a slight tick but its hard to say cause the lifters are always noisy since I've pretty much had the car, especially at start up till everything gets warm. I pulled plug wires on the spark plug sides and tested spark, it jumped to the valve cover. Took off the Ignition Coil side and spark jumped from each plug wire to the ignition coil. (Also confirmed the plugs themselves seemed fine, and not wet at all).

So what does that leave me with, a head gasket issue or a bent valve issue. No water in my oil that i can see. No oil in the coolant by any means I can see. No known leaks coming from the head of leaking fluids of any kind. And again spark plugs are dry as a bone.

Took the valve cover off, do not see anything obvious. Did another compression test(after putting the valve cover back on enough to stop oil from flying everywhere) and this time i got slightly lower numbers but still within spec. 170,161,166,174 going 1,2,3,4 cylinders. Above 133 and JUST within variance with 13 psi between best and worst cylinders.

So point of all of this is, Do such compression readings alone definitely say its a bent valve? Bad head gasket? I've mostly read that if a valve is bad, you will have NO compression in that cylinder. If the valves are only SLIGHTLY bent, would that explain the symptoms?

How can I definitively know its bad valves without taking the head off. Its a job I've done multi times but I just HATE doing especially without a definitive reason to do so. If I go though all that work just to find the valves are fine and its something else, I might loose my mind . But if its NOT the valves what the hell else could it be?

Sorry for the long post/book. Just wanted to cover all the bases for the mechanics better than myself out there.

Thanks in advance.

 

[NOSLO2PT0]

Leak down test

 

[nismojones]

You wouldn’t get readings that high with bent valves ever. You might’ve burned em a bit and reduced sealing but it sounds like you will have to remove the head and inspect the gasket. I would suggest decking the head, new headgasket, and cleaning up the valves. My $.02 anyways

 

[1990TSIAWDTALON]

Slip a borescope into the sparkplug holes and get a look. If you have a phone with a camera, this is a good deal or even this.

 

[ShadyDoins]

Just relax and think rationally. You pulled the valve cover, you pulled all the timing covers, the motor mount, all the other stupid junk in the way, i am hoping you put a new tensioner in which means at some point you had tension off of the timing belt.

You literally did half of the work to pull the head, then you put it all back together, now if you need to pull the head you have to redo everything you already did and also put back everything you already did. By the time you get everything done you will have done 4x the amount of work you needed to.

Out of your available options of what is wrong, what are the options you can fix without pulling the head?

 

[roadtrip_69]

Thanks everyone. I decided to give a leak down test a try. Bought a cheap 30 dollar kit on Amazon. Now it was definitely cheap as I could NOT get the gauge calibrated correctly and one of the tiny screws holding the face plate down on the gauge came loose and was just floating around. None the less, decided I couldn't tell HOW MUCH air its loosing percentage wise, due to the gage. But if the head gasket or valves was bad enough I should get some idea what the problem was.

So this is what I got. Pretty sure the gasket was/is the remaining issue. But the results of the test are baffling to me.

I was getting lost air between cylinders 1 and 2, (though inconsistently, like right away it did but after a second test after testing another cylinder it switched between 1 and 2 to 1 and 3.) not between 2 and 3, but then between 3, and 1. Obvious air, could feel it coming out. I get the between 1 and 2. But how in the hell does it travel from 3 to 1 without also coming out of 2???

I did run the test without the engine being very warm. (Because last time I tested it idled much better, was holding a steady -18-19 vacuum but started to backfire, with loud pops after running for a bit. So didn't want to damage anything else while trying to find the main existing problem. Well it was about 95-100 degrees just due to ambient temps in my garage. But I don't think that would have any baring on the headgasket, right? The rings I'm sure were not as sealed as if the car was warmer with the thermo expansion. But the gasket is sealed via constant static pressure via the ARP studs..

In addition it was also detectable in the coolant just enough to force it out an existing leak I also discovered on one of the banjo bolts ...or maybe coming from the head gasket itself, not sure couldn't definitively find the source before I decided I had to take the head off any way at this point. But it was between the block and the back of the turbo. A steady drip when applying 90 psi of pressure to the 2/3 cylinders (forget which)

So head gasket (99.9 percent sure) is bad. Valves? I still don't really know. But guess I'll have them checked anyways when I get the Head checked out and decked. I already have replacement valves and lifters from a previous "valve issue" in that case it ended up just being an air in the lifters issue after the bottom end build, but i ended up holding on to them, thankfully.

Starting to think this was just a perfect storm event, where I had multiple unrelated issues that became related issues.

Decided to go with a OEM Mitsubishi Gasket this time. Had a felpro before. I did have the block machined when i had it over bored but that was a year ago so not confident its 100 percent without imperfections at this point so scared to put on an MLS gasket and have it leak. Only want to have to do this job once.

Any one ever experience the issue with the 1 and 3 cylinders? How do you leak from one to the other without 2 leaking, or at least not leaking that much in comparison?