1991 RT/TT - First Failure in 230K / 17 years

[cbatters]

Originally Posted by 3Sfever

I just noticed this thread. Back when I was replacing my VSS, mine made a hissing sound when I applied pressure to cylinders also. It seemed to be leaking past the rings, not valves. The engine was cold, which I imagine made it worse. Your engine is cold also, I would assume

Good luck. No fun when things like this happen to daily driver.

How many miles on your timing belt tensioner? (the device with spring and plunger). Mine was shot at 150k. not sure if it was original or not.

Thanks for the heads up..

Unless you tested for leaks before you replaced the rocker arms (or you uninstalled the lifters and purged the oil from the lifters) there is a good chance some of the valves were being held open by the lifters.

(Since I got heart failure when I saw near zero compression following my front head replacement a couple years ago, I always purge the oil from the lifters to make sure the valves close and I can get reasonable compression measurements. They start up very noisy due to excessive clearances but quiet down in a few minutes.)



Clint

[Struggly]

Originally Posted by cbatters

Also encouraging that all of the cylinders appear to be the same.

Clint

Hey Clint, nice to see you post--though it's unfortunate that you've run into trouble.

I agree that all cylinders sounding the same is a good thing. If you had some valve damage, it would be unlikely for all 3 to sound the same.

You said 1 cam on the rear bank was off 2 teeth, and the front bank was fine? I assume the crank pulley was lined up correctly...?

You also mentioned a spun bearing a few posts back. Just speculation, or a legitimate concern? Have you inspected the oil?

Clint

[3Sfever]

Originally Posted by cbatters

Thanks for the heads up..

Unless you tested for leaks before you replaced the rocker arms (or you uninstalled the lifters and purged the oil from the lifters) there is a good chance some of the valves were being held open by the lifters.

All cylinders produced a "hiss" under these conditions: Cams/rockers removed, piston at either TDC or BDC, pressure in sparkplug hole. As mentioned before, this was with cold engine.

My plan was to use the air pressure to hold the valves shut while changing VSS, but found that I could do it with the piston at TDC, and no pressure.

[cbatters]

Originally Posted by 3Sfever

All cylinders produced a "hiss" under these conditions: Cams/rockers removed, piston at either TDC or BDC, pressure in sparkplug hole. As mentioned before, this was with cold engine.

My plan was to use the air pressure to hold the valves shut while changing VSS, but found that I could do it with the piston at TDC, and no pressure.

Appreciate the clarification - sounds like a little hissing is normal.


Clint

[cbehnken]

Originally Posted by cbatters

Appreciate the clarification - sounds like a little hissing is normal.


Clint

Well, if you pressurize the cylinder with 100 PSI and have only 5% leakdown (good race engine spec) you'd still have 5 PSI of pressure getting past the rings. That should be audible to anyone. Figure a more realistic figure of 10-15% for a high mile stock engine and you have a lot of air going past the rings.

[cbatters]

Originally Posted by cbehnken

Well, if you pressurize the cylinder with 100 PSI and have only 5% leakdown (good race engine spec) you'd still have 5 PSI of pressure getting past the rings. That should be audible to anyone. Figure a more realistic figure of 10-15% for a high mile stock engine and you have a lot of air going past the rings.

Sounds encouraging. I am going to see if I can scrounge up a timing belt and tensioner to re-install tomorrow and get the beast back on the road.

Just in case I strike out at the Mitsu parts store, does anyone in MA have a timing belt and tensoner they are willing to sell?



Clint

[mike92stealthtt]

Before I started my 120k I found that my front intake cam was 2 teeth clockwise and my rear intake cam was 2 teeth counter-clockwise. I went along with my 120k (timing belt/oil pump/lifters/VSS) and then at the end checked my compression. I got 150's across the board with a COLD test which really surprised me.

So if I were you I would wait on the new tensioner/timing belt and get the timing marks all lined up and start her up. You could probably get away with using the old tensioner/t-belt for a little while if you are still able to slide the pin in the tensioner after waiting the 5 minutes and the belt doesn't have any cracks.

Edit: Checking the compression before starting it up again is what I meant to say but you knew that. Maybe I just start to become dumber after 1 AM?

Also I would check to see if your cam seals are leaking because they could have potentially led to the belt slipping a few teeth (one of mine was badly leaking).

And yes I did hear hissing while doing my compression test and had each piston be at TDC rather than using air pressure.

Best of luck

Mike

[cbatters]

Originally Posted by mike92stealthtt

Before I started my 120k I found that my front intake cam was 2 teeth clockwise and my rear intake cam was 2 teeth counter-clockwise. I went along with my 120k (timing belt/oil pump/lifters/VSS) and then at the end checked my compression. I got 150's across the board with a COLD test which really surprised me.

So if I were you I would wait on the new tensioner/timing belt and get the timing marks all lined up and start her up. You could probably get away with using the old tensioner/t-belt for a little while if you are still able to slide the pin in the tensioner after waiting the 5 minutes and the belt doesn't have any cracks. If it starts up and idles fine I would do another compression test and hope that taking off the heads isn't the next step.

Also I would check to see if your cam seals are leaking because they could have potentially led to the belt slipping a few teeth (one of mine was badly leaking).

And yes I did hear hissing while doing my compression test and had each piston be at TDC rather than using air pressure.

Best of luck

Mike

Thanks for the friendly advise... I have already cnfirmed that the valves and rings appear to be sealing correctly so the next steps on the path back to driving is to:

1. Install a new timng belt and tensioner
2. test compression
3. Fire up the beast and see if the noise is still there

Note: I have done 2 - 60Ks on the car myself and am 20K overdue for a third so I want to install a new belt. Also, I swapped front head at ~170K with a fully loaded head that only had 40K on it and have another fully loaded head to toss in the rear if I have valve damage. (I have always wanted to toss in the new head - just have not had the time.



Clint

[cbatters]

Still scrounging around for parts.


Does anyone in Easter MA have a 60K set of parts that I can borrow and replace when my OEM parts arrive next week?

(I have found some ag\ftermarket parts but still short a couple cam seals and would prefer to use a Mitsu OEM timing belt.)



Clint

[cbatters]

Finally got around to installing timing belt and firing up engine. Same nasty sound.

Facts:

1. 150 PSI +/- 2 PSI across 1-6
2. Disabling spark on cylinders one at a time had no affect on sound
3. Vacuum is rock stable at 20 in/hg
4. Sound is REALLY loud and nasty. Sounds like it is coming from rear bank near #2 cylinder.
5. Once in a while the sound stops but then resumes

Appreciate any input.




Clint