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DimensionDude
May 22nd, 2006, 06:35 PM
A friend has given me two Toyota Corollas. Both are 1987 models, the only difference is that one is an LE (nicer seats, OD trans, extra trim). The catch is that neither one runs. The LE was used as a postal delivery vehicle on a rural route so it's kinda rough looking. She (my friend) let it run low on oil and apparently spun a bearing on the crankshaft. Actually, this one will run but with a diesel-like clatter that is horrible to hear.

The other one is in excellent condition. No dents, not even a scratch. The top end of the motor is in the trunk. Neither of us has any idea why the motor is half torn down, she bought it like that with the intention of pulling the motor out of the LE (before she damaged it).

Can't really find anything wrong with the top end, head, valves, combustion chamber looks good. Bottom end turns freely, absolutely no wear in the cylinders, light carbon buildup on top of pistons.

My plan is to put the head back on it and run a compression test. Might have bad rings or something.

Kent

DimensionDude
June 7th, 2006, 02:42 PM
An update on this project.

Got the surface rust out of the cylinders and reinstalled the head (with a $30 head gasket). Ran a compression test. Apparently this motor is missing some piston rings. Dry compression readings for cylinders 1-4 in order is 130, 60, 60, 45 PSI. Yikes! Didn't even bother with a wet test.

Just for a lark I ran a compression test on the other car. I got 175, 135, 145, 170 PSI. Guess I'll have to tear this one down and find out just what is knocking.

May be able to use parts from both motors to build one working motor.

Kent

carlsson
June 7th, 2006, 03:10 PM
It sounds like fun, if you know what you're doing. I basically know how to change oil and battery on a car.

However, one day I will read up on how to service woodwind, and give my old alto sax, battered beyond recognition, a go. I suppose I will end up needing a number of fresh pads, probably corks, straighten rods and some stuff I'll not even be able to do. I know it is a craft that it takes years and special courses to master. I just figure out that handing in that alto to a professional (or even semi-professional) repairman doesn't justify the cost. It would cost almost as much to restore it as it is worth after the fix-up.

Terry Yager
June 7th, 2006, 03:14 PM
A common error is to run a compression test on a cold engine. Wet or dry, you can't get a true reading that way. A cold piston (and therefore, the coresponding rings) are not round, while the cylinders are. Pistons are slightly eccentric, with the wider point along the axis of the pin. This is done so that when the piston becomes heated, it expands less along the pin, where there is more metal. When heated, the piston becomes nearly perfectly round. Cold, unexpanded pistons/rings will always leak.

The purpose of the 'wet' check is to determine whether a low compression reading is due to worn rings or some other cause (gasket, leaky valve, etc), the theory being that the oil will form a temporary seal between the ring & cylinder wall, and raise the compression reading significantly over that of the same jug when dry.

--T

Terry Yager
June 7th, 2006, 03:23 PM
Oh, BTW, a new head gasket doesn't seal tightly until it's heated up either, unless you use good 'self-sealing' gaskets. I've always liked Fel-Pro gaskets, although they cost a little more. There may still be hope without tearing the engine down again. I have seen engines that would start up and run with as little as 45 psi compression.

--T

DimensionDude
June 7th, 2006, 04:12 PM
Yeah, I know that a cold reading isn't accurate, but it's usually in the ballpark. The readings on the LE (the higher set of readings) was cold, too.
What bothers me the most is that one decent reading. If all 4 had been equally low, I would have put it off as being cold.

I suppose that I could get it to the point where it will fire, just to see how much it smokes. Hey, could get a contract as a mosquito fogger. :)

Kent

Terry Yager
June 7th, 2006, 04:20 PM
Yeah, with those readings, I'd suspect head warpage, but I'm assuming you already checked it for trueness before assembling it. Did you use new head bolts? (Some engine designs require 'em).

--T

Terry Yager
June 7th, 2006, 04:24 PM
The good news is that Toyota engines are almost un-killable (I've got some great stories). I'm confidant that you'll be able to get one or both on the road soon.

--T

Terry Yager
June 7th, 2006, 04:35 PM
If it were me, I think I'd grab the crank out of the one & slam it into the other.

--T

DimensionDude
June 7th, 2006, 04:56 PM
If it were me, I think I'd grab the crank out of the one & slam it into the other.

--T

That's what I've decided to do. Thing is, you have to pull motor/transaxle as an assembly. Maybe I can borrow an A-frame from someone.

I'm hoping that I can pull the oilpan off the LE without pulling the motor, then I can see just what damage has been done to the crank. May not even be a rod knocking, but that's what I'm betting on. Guess I could check the cam for oil starvation before I get too deep into it. The knock goes away at idle so I'm crossing my fingers that the damage isn't too severe.

A car that gets 30MPG in mixed driving (last check on the LE before the engine went CLUNK) will be a vast improvement on my Jeep's 14MPG.

Oh yeah, the car with low compression shows evidence of blowing oil into the engine compartment so I'm leaning towards bad (really bad) rings.

Kent

Terry Yager
June 7th, 2006, 05:02 PM
Worn valve guides/seals can cause a lot of blow-by too.
Oh yeah, did ya disassemble all the valves and coat 'em with some good build-up lube after the head sat around for so long? Could be just that some of them are sticking open a little.

--T

DimensionDude
June 7th, 2006, 05:25 PM
Worn valve guides/seals can cause a lot of blow-by too.
Oh yeah, did ya disassemble all the valves and coat 'em with some good build-up lube after the head sat around for so long? Could be just that some of them are sticking open a little.

--T

No, didn't disassemble the valves. My valve spring compressor has disappeared.


Here's something for you to see. This happened around 1980-1981 or so when I was going to junior college. On my way to school one day, my 71 VW Super Beetle started losing power and making more noise than usual. Looked in the mirror and saw a huge cloud of smoke. Pulled off the highway, the engine idled but made a loud clunk on each revolution.

This prompted my first engine rebuild, I guess that's why I've kept it all this time. Can't see it in the photo, but the rod is twisted. Found bits of piston in every cylinder, broke every ring.

Kent