The other day after my fiasco at the mechanics, I took the car out for a lil road test and about 50 miles out, she overheated and was losing power after running fine for the previous two days. I put the clutch in, let the engine die and coasted for as long as I could to keep air moving through the radiator and engine compartment. Instead of trying to drive it any further, I parked it on the side of the highway and came back with a dolly the next day.
Today I filled the cooling system and burped it before moving it. I also checked the oil to see if there was any water in it. No water in the oil. Whew.
At around 2500-3000 rpm I get an engine knock. I know this sound all to well as this was the start of all my problems 8 months ago when I destroyed the last motor by putting a rod through the block.
Is this sound coming fron a rod bearing and if so, do I have to drop the motor to replace it or can I do it with the car on jackstands and just pull the oil pan?
Also I noticed that the oil pressure is not as high as it should be on a rebuilt motor even before this new problem materialized. I am sure that the ID-10-T that rebuilt the motor charged me for things he didn't do as the new cam and lifters will attest to. Guess I might as well replace the oil pump while I'm at it.

Most people know to look for cracked block/head and blown head gaskets after a big overheat...

Another thing that can happen... You may have cooked the rings. The top ring is often the first to go when this happens. Engine knock often results.

If you cooked a ring, a compression test may show it up. Depends how bad it cooked. You'll need to do the compression test both wet and dry for each cyl. Ideally you want the same number of piston strokes on each test as well. Or as close to it as posible. Best if you get a remote starter switch. This connects directly to the starter and gives you much better controll. (It's just a fancy heavy duty push button.)

You could have damaged the bottom end. It's posible but that wouldn't be my first choice.

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Screamin' Yellow Zonkers... If it's Screaming and Yellow, I aint eatin it.

I know how to do a dry test but how much oil do you use on the wet test?

Paul

Only enough oil to help the seal. regular motor oil. A half to one ounce max. Too much and you could make the cylinder lock when you put the plugs back in.

The tricky part is trying to get it on the cylinder wall.

With an inline motor you can often get away with just squirting some in and wait for it to spread.

If the car is on a slope or especially on V or slant engines. If you just pour it in, it goes to the low side and you may never get the cylinder wet enough for the test to be accurate. To solve that problem...

First I make sure the cylinder is most of the way down. Gives you room to get in there.

Then I use a syringe with a bit of copper or stiff plastic tubing bent as needed so I can squirt it around and get the oil on the walls. Just squirt it in thru the plug hole.

Keep in mind, the thing will smoke like hell for awhile after you start it again. You don't want it indoors when you do that.

Rod knocks can be determined by two ways,
With the car in park and running quickly open and shut the throttle. The rod will knock as the engine is dropping back down to idle.
Or you can pull one plug wire at a time.

Crank knock is easiest to hear while the engine is under a load.
Put it in gear and slip the clutch with the ebrake on, or if an auto put it in gear and give it a little gas while you have your foot on the brake.

quote Originally posted by theogre: The tricky part is trying to get it on the cylinder wall.

Makes sense, I was taught to use engine fogger. I never questioned it before, but now I know why.

I have been driving it very carefully for short distances and I get knocking when I start the engine. When the motor runs up at start up and at around 2500-3000 rpm is where it knocks the most before shifting. I took it up a hill in 4th and it didn't seem bad at all. Mainly knocks when the revs get above 2500 rpm.
I am going to have a friend come over tomorrow I hope and do a compression test on it.

I had an overheat result from a clogged radiator. It didn't register on the temp gauge until after the radiator blew up to show there was a problem. Shortly afterwards a knock developed. I finally changed the engine when blow by got out of hand. I broke the engine down to find grooves in the main journals as deep as a dime is thick.

I just finished with a dry compression test of all cylinders with WOT and came up with the following results.
1. 140psi
2. 140psi
3. 145psi
4. 140psi
5. 130psi
6. 140psi
As you can tell all the cylinders with the exception of #5 seem to have plenty of compression and even #5 isn't that low.
I did notice that all 3 of the back plugs (2, 4 & 6) were finger loose and were allowing gases to escape past them but I corrected that when I put them back in.
Should I still wet test the cylinders with it being this close on all cylinders?

I don't know if a wet test will tell you much...

There are several things that could be causing it... including EGR problems and stuff like that. It could be caused by the over heat or just a coincidence. So don't rule out all the normal stuff. Check the timing and vac leaks and all that junk.

As I remember... the dif from highest to lowest should be within 20PSI. Closer is of coarse better.