My Supra is sick, please help me!

rnoswal · 09-06-2005, 01:42 AM

Well there really are no lifters on your overhead cam engine. The cam rides directly on a shim that sits in a bucket that pushes directly on the valve. The tolerances are tight so that is why there is none of the clicking noise on a normal solid tappet design. That is not where your problem is though unfortunately.

Down deep are the connecting rods and they are usually the first casualty when something gets starved of oil. If your engine is a few quarts low and you hit the brakes hard or go into a turn hard, the oil sloshes away from the oil pump pick up and starves the system of oil. The coating on the bearings quickly heats up and melts away the lead base part of the bearing and rubs on the crank and it gets worse from there. Normally there is only a few thousandths clearance between the bearing surface and the crank so at start ups in the mornings there is probably a very slight but non detectable rattle, but the oil film that is there and the oil that quickly builds up takes up that space and the oil cushions that clearance.

If the surfaces get worn away, normally or due to a lack of lubrcation, then the clearance gets too large for the oil to cushion and the bearing surface hits on the crank, especially on the compression stroke and that is when you get that deep rattling sound form the bottom end. As you can guess, the bearing needs to be replaced and usually the crank needs to be reground. While you are there you start checking other parts and find that you may need pistons and main bearings, head milling and block resurfacing and then at least you need to replace the valve stem seals.

The rear seal does dry out and starts leaking. They are cheap and relatively easy to replace, but not everyone has the facilities to do that, so keep pouring in the oil and hope, but eventually........well you know, low oil, then the death rattle, or worse. I just got an 87 Supra that had the same problem it looks like. The owner, who had the junkyard pick it up said he thought it was the timing. Beautiful car but it wasn't the timing as much as it was the large hole on the passenger side of the block! That is what happens if you let it rattle too much. Also it looks like it caught fire in that area too!

Good luck, but get it rebuilt by someone that knows at least a little about foreign cars.

Russ

09-06-2005, 01:42 AM	#4
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Well there really are no lifters on your overhead cam engine. The cam rides directly on a shim that sits in a bucket that pushes directly on the valve. The tolerances are tight so that is why there is none of the clicking noise on a normal solid tappet design. That is not where your problem is though unfortunately. Down deep are the connecting rods and they are usually the first casualty when something gets starved of oil. If your engine is a few quarts low and you hit the brakes hard or go into a turn hard, the oil sloshes away from the oil pump pick up and starves the system of oil. The coating on the bearings quickly heats up and melts away the lead base part of the bearing and rubs on the crank and it gets worse from there. Normally there is only a few thousandths clearance between the bearing surface and the crank so at start ups in the mornings there is probably a very slight but non detectable rattle, but the oil film that is there and the oil that quickly builds up takes up that space and the oil cushions that clearance. If the surfaces get worn away, normally or due to a lack of lubrcation, then the clearance gets too large for the oil to cushion and the bearing surface hits on the crank, especially on the compression stroke and that is when you get that deep rattling sound form the bottom end. As you can guess, the bearing needs to be replaced and usually the crank needs to be reground. While you are there you start checking other parts and find that you may need pistons and main bearings, head milling and block resurfacing and then at least you need to replace the valve stem seals. The rear seal does dry out and starts leaking. They are cheap and relatively easy to replace, but not everyone has the facilities to do that, so keep pouring in the oil and hope, but eventually........well you know, low oil, then the death rattle, or worse. I just got an 87 Supra that had the same problem it looks like. The owner, who had the junkyard pick it up said he thought it was the timing. Beautiful car but it wasn't the timing as much as it was the large hole on the passenger side of the block! That is what happens if you let it rattle too much. Also it looks like it caught fire in that area too! Good luck, but get it rebuilt by someone that knows at least a little about foreign cars. Russ Last edited by rnoswal; 09-08-2005 at 02:32 PM.