Mitsubishi 3000GT & Dodge Stealth Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi everyone, this is my first post on this forum. I have a 1991 3000gt VR4 with 100k miles and a couple months ago I was driving it and mildly accelerating in 2nd gear when the engine started rapidly knocking. Here is a video of the knocking: 1991 3000gt VR4 Spun Bearing
I’m not sure if it’s rod knock or piston slap?
After it started knocking it was still able to drive, I drove it about 3 miles back to my house and parked it where it still sits. I’m currently pulling out the engine to hopefully get it rebuilt, do you guys think there is hope of rebuilding it? Does it sound like rod knock or piston slap? Let me know with any advice you guys have.
 

·
Senior **i.e. OLD** Member
Joined
·
15,404 Posts
I've never experience either of your suggestions, but to me that sounds more UPPER end.
Like maybe a rocker came off.

Might be worth it to see if you can pinpoint the noise from the front bank or rear.
If it sounds like front, I would pull that front valve cover and give it a looksee.

Just my .02

Bob.

EDIT: Even if it sounds like rear, it's not that hard to remove the plenum and get that back valve cover off too.....
 

·
Registered
1994 3.5 sawp
Joined
·
71 Posts
Ya sounds like my carLol

How does your oil pressure look like? low at idle?
how does it feel with rpm, worse or get softer?

And after valve cover if you can't find anything up top wrong then the next thing would be drop the oil pan and look for a sloppy rod
 

·
Money pit owner.
Joined
·
2,847 Posts
yikes that sounds terrible. i would also check the timing belt tensioner by removing the front upper timing cover and peering down at the tensioner with the engine running.
do you know if the 60000 mile service was done?
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #6 ·
I've never experience either of your suggestions, but to me that sounds more UPPER end.
Like maybe a rocker came off.

Might be worth it to see if you can pinpoint the noise from the front bank or rear.
If it sounds like front, I would pull that front valve cover and give it a looksee.

Just my .02

Bob.

EDIT: Even if it sounds like rear, it's not that hard to remove the plenum and get that back valve cover off too.....
Thank you very much Bob. I’m about halfway done with pulling my engine so taking off the plenum is very easy at this point. Hopefully you’re right on this because a fallen rocker is definitely better than a spun bearing.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #7 ·
yikes that sounds terrible. i would also check the timing belt tensioner by removing the front upper timing cover and peering down at the tensioner with the engine running.
do you know if the 60000 mile service was done?
Ya sounds like my carLol

How does your oil pressure look like? low at idle?
how does it feel with rpm, worse or get softer?

And after valve cover if you can't find anything up top wrong then the next thing would be drop the oil pan and look for a sloppy rod
Oil pressure is very low on idle, previous owner claimed gauge wasn’t accurate but I’m not too sure about that. When given RPMs the noise gets a lot worse, faster rapid knocking. I’m really hoping it is a rocker arm.
 

·
Registered
Joined
·
474 Posts
Oil pressure is very low on idle, previous owner claimed gauge wasn’t accurate but I’m not too sure about that. When given RPMs the noise gets a lot worse, faster rapid knocking. I’m really hoping it is a rocker arm.
I know I’m a little late on this, but that start up is definitely bottom end noise. The was a massive amount of rattle until oil pressure came up high enough that it revealed the remaining failed bearing. That said even if the gauge is inaccurate, you can still judge the amount of pressure you have as adequate or lacking.

My car has 123,000 on it and when you start it cold the pressure gauge goes over the halfway mark on the gauge. When it’s warm at idle the gauge is just under 1/3 to right at 1/4 of the way up, depending on if I run 15/40 or 20/50 for the protection against the heat we have here in Texas.

Not that long ago, my front crank seal failed without me knowing on my way to work. I started the car to go home and I heard a hint of rattle checked my pressure gauge and saw no one home so I shut it down. Looked under the car saw the issue and then decided to do the front crank seal right then and there in the parking lot. 3hrs and 50 minutes later I had the car running on 15/40 with no leaks but I noticed the pressure gauge at warm idle was a touch under the 1/4 gauge area, and at highway speed it was a little under the half way mark on the gauge so I drove it home and parked it. No noise or anything, but it was obvious that it that the original high mileage rod bearings are compromised. FYi there seems to be a delay in getting certain types of bearings. I ordered a set of racing bearings from Jegg’s and they drop ship directly from Clevite and it’s been over 6 weeks. I went and just got Clevite street bearings in standard size off the shelf from Orielley’s Auto Parts and am just gonna use those for now, but as bearing clearances open up oil pressure takes a dive.

Generally speaking if the oil pan is dented or damaged anywhere on the bottom, if the bearings are shot, if the oil pump is worn out, or if the oil pressure relieve valve is allowing leak down any of those issues can result in the gauge reading low despite it not telling you exactly how much pressure is actually there. The only other thing that can cause a low gauge reading is a clogged or failing oil pressure sending unit. Treat it as a dummy light for people who would rather have a gauge than a light. If the gauge normally reads a specific area at running temp and it comes up low, you know you’ve got an issue somewhere. Just my 2.5 cents lol. Good luck on the rebuild brotha-
William-
 
1 - 8 of 8 Posts
Top