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Cylinder Wall Pitting/Damage


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I've already talked to Dad about this a bit, posting here for a wider audience and to possibly help anyone else who may run into this.

In my quest to determine why my intercooler keeps collecting oil, I decided this weekend to do a cylinder leak down test. Prior to doing this, however, I decided to get my borescope and take some pictures of the cylinders while I had the spark plugs out. Lo and behold, it appears I have found the cause.
Cylinder 1:
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Cylinder 2:
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Cylinder 3:
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Cylinder 4:
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Because I was already most of the way there, I decided to go ahead with the leak down test, here are my findings:
Cyl 1: 12-14% leakage
Cyl 2: 7-10% leakage
Cyl 3: 19-21% leakage
Cyl 4: 7-10% leakage

Other than all the smoke it produces on start up, my Quest seems to run about as good as I'd expect a large 4 cylinder from the 80s would. I was already planning to go through this engine prior to the test, as it's history is very unknown, but this does solidify my plans.
My question is, what could have cause this damage? I have a few theories on what I have done which may have caused this, but I'd like to hear what you all have to say before I start beating myself up :D

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5 minutes ago, Caliber308 said:

Has it been humid where you live, and how often do you drive your Starquest?

Bill

Pretty sure it's always humid here by Arizona standards. I drive mine to work about 1-2 times a week, nearly 80 miles a day when I do. If it's sitting for any period of time, it's in a garage.

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The reason I asked is because no.3 and 4 look like a bit of rust accumulation. Running it 1 or 2 times a week might scrub off rust further down in the cylinder walls. What did Dad say about it?

Bill

Edited by Caliber308
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3 hours ago, Caliber308 said:

The reason I asked is because no.3 and 4 look like a bit of rust accumulation. Running it 1 or 2 times a week might scrub off rust further down in the cylinder walls. What did Dad say about it?

Bill

He said it looked like detonation or coolant being burnt. There have been times where the car's run lean on me, but I don't think anywhere near enough to cause this kind of damage, especially with the 93 I put in it. As far as the coolant goes, ever since I sorted the coolant leaks, the fill level's been 100% steady, I never have to top it off.

2 hours ago, obsolete said:

Did the car sit for a while before you got it? I agree, looks like rust pitting.

Not that I'm aware of, but I don't have very much info about the car's history. Going off of the VIN history, it seems to have a legitimate 163k mileage reading on the odometer. The only time I think it may have sat would have been during the alleged engine rebuild that was 20k miles/10+ years ago.

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It's hard to decipher what I'm looking at there.  Not sure how deep the pitting really is.   

The leak down test actually looks pretty good.   10-15% is pretty normal.  Although, i'd be a little concerned with cylinder #3 being that it deviates from the rest by so much..and possibly #1 too.   Does this car still have jet valves?   Mechanical rocker arms for the int/exh valves?   If so, are they gapped correctly?   It definitely doesn't take much to open up a jet valve.   DId you notice any sign of air leaking into the intake or exhaust during the test?   If a valve is held open, you will hear it fairly clearly out of the intake side (through the open throttle body being that your OVCP is off for the test).   Might be worth undoing your downpipe on the exhaust side.     

I also like to do a leak down test with a coolant pressure test gage on the radiator.  I typically pressurize the coolant system to 13 psi and then perform my leak down test...while watching the coolant pressure to see if it rises.   Then release the pressure down to under 5 psi and try it again.    I had an increase of over 2 psi and rising in the coolant system during the leak down test on my one car which ended up being a leaking copper head gasket.   I also had no indications in the coolant system, nor any overheating or bubbling in the slop tank,  but it was very clear the HG was leaking when I pulled the head.   Had a full thread on that issue here, but it is now gone.    Anyways, it might be worth redoing the test to rule out coolant leakage.  That may be the source of the pitting.  

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3 hours ago, kev said:

It's hard to decipher what I'm looking at there.  Not sure how deep the pitting really is.   

The leak down test actually looks pretty good.   10-15% is pretty normal.  Although, i'd be a little concerned with cylinder #3 being that it deviates from the rest by so much..and possibly #1 too.   Does this car still have jet valves?   Mechanical rocker arms for the int/exh valves?   If so, are they gapped correctly?   It definitely doesn't take much to open up a jet valve.   DId you notice any sign of air leaking into the intake or exhaust during the test?   If a valve is held open, you will hear it fairly clearly out of the intake side (through the open throttle body being that your OVCP is off for the test).   Might be worth undoing your downpipe on the exhaust side.     

I also like to do a leak down test with a coolant pressure test gage on the radiator.  I typically pressurize the coolant system to 13 psi and then perform my leak down test...while watching the coolant pressure to see if it rises.   Then release the pressure down to under 5 psi and try it again.    I had an increase of over 2 psi and rising in the coolant system during the leak down test on my one car which ended up being a leaking copper head gasket.   I also had no indications in the coolant system, nor any overheating or bubbling in the slop tank,  but it was very clear the HG was leaking when I pulled the head.   Had a full thread on that issue here, but it is now gone.    Anyways, it might be worth redoing the test to rule out coolant leakage.  That may be the source of the pitting.  

Yeah I've been kinda wanting to re-do the test because of the cylinder 3 reading. Even though I did it twice (hence the 19-21% range), I think both may have been faulty readings. Cylinder 4, the one I tested right after 3, was initially reading the same thing, but after I shut off the gauge to let my compressor repressurize, it started reading around 10% loss when I tested #4 again. I'll try again this weekend with a coolant system tester.
Probably should have mentioned this off the bat, but I've got a non-jet valve head and the hydraulic rocker pills. I didn't hear any noise coming from the intake or exhaust, but admittedly I wasn't listening for it.

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At that leak down you should be able to hear what’s leaking. Pull the oil cap and intake pipe and you can tell if it’s intake or exhaust valves or rings. Add oil to the cylinder and see if readings drop. When I build engines they are 1-3% leak down. At 5-8% I would tear down to investigate. 

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Alright, so I just finished doing this a second time, and the readings are a touch better across the board, even though I didn't do anything except drive it since the last test:
Cyl 1: 12-10% leakage
Cyl 2: 8-8% leakage
Cyl 3: 17-17% leakage
Cyl 4: 10-7% leakage

For both tests on each cylinder, I did pressurize the coolant system per kev's suggestion, first test at 13 PSI then again at ~5 PSI for the second test. There was no drop or gain in coolant pressure during any leak down test, so I'm pretty confident my head gasket is in good order. I did listen for the leakage this time, and each time I heard it through the oil cap and rear valve cover port. I heard nothing through the intake or through my O2 sensor hole, so I believe the head/valves are in good order as well. I elected to not spray oil into the cylinders this time around because I feel it's a bit redundant with the known condition of the cylinder walls, but I do understand it's purpose had they been in good visible condition. I have plans for this engine, and one of them is definitely pistons/rings.

If this pitting happened in my ownership, there's only one event that I think may have caused this. Back when I had idle issues, I had determined it was caused by the 1g DSM recirculating valve the PO had installed, but didn't have "crushed" for blow-off, so it was leaking vacuum at idle. At the time, I didn't know that they needed to be crushed; I just thought it was faulty. So, I just bought another used one in reportedly good condition, installed it, and went driving around DFW one day trying to find a body shop who would work on my Quest. I learned shortly into my drive that the new recirc valve had actually made things worse; my wideband was buried at 10:1 all time time, regardless of engine load. I was kinda pissed because I had looked damn near everywhere else trying to find the cause, so I just ran with it. I put about 100+ miles on the car that day, calculated I got about 9 MPG to that tank of gas when I filled up later. I'm wondering if running that rich for that long would have caused this.

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Running rich like that just washes the oil off the cylinder walls and dilutes the oil. If it was a fresh engine and you did that you might have sealing issues but on a engine with miles on it I wouldn't expect anything and especially not pitting.  I think at some point water / coolant got into that engine and it sat a while. 

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