Re: 230 oil pressure?


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Posted by David Sherman on Sunday, May 03, 2009 at 20:25:32 :

In Reply to: 230 oil pressure? posted by Jon Martin on Sunday, May 03, 2009 at 19:47:10 :

I just drove my M43 for the first time with known good gauges and senders and it's showing 30 lbs at idle or reved up, hot or cold. I'm not sure I trust the gauges on the sno-cats or the running M37, but they tend to show in that range too. I think the M37 goes lower when warm, and is definitely much lower at idle, but it only has 90 lbs of compression, probably because when I got it it had no air cleaner and had been driven that way for quite a while.

You didn't exactly say that your 5 lbs is at low idle. If it pops up to 30 as soon as you give it some gas, I wouldn't worry too much. The manual no doubt assumes straight 30 weight oil, hence the big difference between hot and cold. I just run 10W40 in everything so as not to have to stock multiple grades and because I can't see any logical reason to use 30 weight nowadays.

Your absolute maximum pressure should be regulated by the bypass spring, so if it never gets near 30 even cold and at high RPMs it's possible the spring is wrong or weak, but since you swapped pumps and regulators, that pretty well eliminates pump wear and a weak spring.

From what you've said, the likeliest possibility is the bearings are worn, sorry to say. You can try all the "high-mileage" additives, thicker oil, STP, etc. They ought to improve your oil pressure, but they won't replace missing metal. I'm not sure how easy it is to replace the bearings with the engine in the truck. If you can get the oil pan off, and if the journals aren't worn too much (check with plastigage or carefully with a micrometer), you might get away with dropping the pan and replacing the bearings. Getting the top halves of the mains out can be tricky. I haven't done it on a 230 yet so don't know how hard it is. For many motors they make bearings that are .003 undersized, the idea being that sometimes that will make up for wear without you having to get the crank ground. Sometimes a new set of standard bearings is all it takes. You may also just have one that's bad and is losing lots of oil. You do want to get to it before you spin a bearing or wear through it into the crank. Unfortunately all signs (to me) point to worn bearings. The only way to really tell what's going on is to drop the pan. You might notice by hand wiggling the connecting rods that one or all feel too loose. Do you hear a rod knock while it's running? With luck, you can just swap in some bearings from the bottom end without having to pull the engine and do a major overhaul. I know nowadays the standard procedure for any internal engine wear is to rebuild or replace the engine but it used to be common practice to just repair enough to get it going again -- a ring job with no machine work for example, a valve grind alone, or replacing a couple worn bearings. It's also possible to grind the crank while it's in the vehicle. I have an old Sunnen crankshaft grinder that does just that. I've only used it once, and it takes some setup, but it's pretty neat.



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