bearcat2

I have a 1989 4x4 pickup with a 22RE that has developed a nasty knock in the motor. Bad enough that if you leave it running for a minute it will start to develop a squeal and die.


I've had these trucks and worked on them for twenty years (since I was old enough to drive) but while I have had at least three with between 300-400,000 I have never had to delve any deeper in the motor than changing the timing chain or once a blown head gasket. So I don't know a lot about the guts of these motors (other than the fact that if you change oil regularly you can beat them like a redheaded stepchild and usually not have problems).


I pulled the valve cover, timing chain is tight, guides look good, oil is good (changed less than 1000 miles ago, clean, no obvious metal or antifreeze) and everything appears to look alright at a glance.


Borrowed a compression tester and checked compression today. It was checked cold because the motor doesn't sound like it will run long enough to warm up. But the throttle was held wide open like I have read you are supposed to on these motors.


cyl 1 105
cyl 2 130
cyl 3 120
cyl 4 120


Cylinder 1 appears out of spec with the others, but still holds some compression, not sure what this tells me?


Truck has 157,000 miles on it, I've only owned it for the last 15,000. I bought it at an insurance auction a year ago (rearended, put a flatbed on it and replaced rear window, good as new) so I don't know the history of the truck. The truck appears to have never been off the blacktop or even drove in the winter when the put deicer on the roads, however. Spotlessly clean underneath, without a drop of rust or corrosion, removing the bed, replacing differentials (with ones I had with lower gears and lockers) etc. was like working on a new truck.


Also it had new brakes, hubs and wheel bearings recently packed, and receipts for said work being done at Les Schwab's in glove box. As well as records of oil being changed regularly at a local shop. So it appears in all respects to have regular maintenance done and other than allowing Les Schwab's to touch it it appears that it was taken excellent care of.


What should I be looking for, could anything in the top end be likely to be causing this, or do I need to look in the bottom end?

Kiroshu

Welcome to YotaTech!

I would verify the "knock" is relative to engine internals first. Are you able to take video?

Is it a fast knock that's heavily exaggerated with engine speed increased..?

If its a connecting rod bearing failure and or piston damage then you can pin point the cylinder it is on by disconnecting spark plug wires one at a time with the engine running. This takes the load of compression from the cylinder changing the noise pitch. If the noise changes(will quiet down slightly) then you have found the trouble cylinder.

Your compression numbers are a little low even for a cold engine. It definatly has some internal wear. #1 may even be the trouble cylinder with that compression drop.

Loose flywheel mounting bolts can also cause a "knocking" sound to resonate through the engine.

No known engine repairs done to the engine..?

What happened when the knock ocuured..? Just a random ocuurence..?

The engine oil was just changed...? Was it by you personally..? Possible tampering and improper service procedures during engine oil change.

Possible bad luck and or harsh operating conditions for the engine.

Verify any loose brackets and or pulleys.

Crankshaft pulley loose/damaged...?

Oil pressure..?

bearcat2

My video camera is broken right now, so no video. The knock coincides with the engine speed, it increases if you increase engine RPMS, not sure what you mean by heavily exaggerated, but if you mean it increases faster than RPMs increase, then no.


No, no known engine repairs.


I always change oil myself, and it was done recently, but not JUST done (have to look under the hood where it is written down, and it is dark right now, but around 7-800 miles ago)


Base model 89, no oil pressure gauge.


I'll crawl underneath when I get home today and see if I can tell anything about the flywheel bolts. All pulleys seemed to be good, but may take fan belts off and double check them without a fan belt holding them tight.

Kiroshu

If the knock increases speed when the engine speed increases it points to connecting rod bearing. However its possible its still something loose. I meant to ask but was the clutch recently serviced? This would be the relation to the loose flywheel bolts possibility. Well if you have no oil pressure gauge then there should be a low oil pressure warning lamp. Dig deeper and let us know.

bearcat2

Oil pressure light does not come on (works when you turn the key on, but goes off as soon as the truck is started) so I assume oil pressure is in acceptable ranges, it makes a mess when you start the truck with the valve cover removed . No recent work on the clutch, I'm unsure if it has ever been touched, but with the amount of miles on the truck (and obvious lack of being used offroad) when I bought it, I doubt anything has ever been done to the clutch. Haven't had a chance to look at anything since I posted this morning.

RJR

The 120-130 compression numbers are about right if you live at 5000-6000 feet. Low if at sea level. The 105 is a concern, since it's signicantly different from the others.