The Stovebolt Site Forums The Shop Area Engine Shop 235 Oil Pressure Issue - Again

I thought I'd bring this up again since I'm about to pull the engine. Please let me know what I should be looking for when I drop the pan. Thanks.

This engine was professionally built about 200 miles ago with all new parts. Two weeks ago I was cruisin down the highway when I noticed my oil pressure drop from 31# to 15#. Over the next 5 miles or so I watched drop to near zero. I shut it down and had it towed home. There was the same amount of oil in the pan as there was when I left the house earlier.

Several days later, I started it to turn it around in the garage and I could hear lifters knocking like they were collapsing. I didn't hear anything at the bottom of the engine. I tried to remove the pan in the truck but they had used black RTV and it was glued on pretty good.

This weekend, I plan to pull the engine and take the pan off. What should I be looking for in this thing? I never had any oil pressure issues in the first 200 miles. Thanks.

Are you taking it back to the builder? I wouldn't do anything that might void your warrenty till they looked at it first.

Jerry,

That is the big question. The pump is either not picking the oil up, or the system has a massive internal leak.

The system feeds the mains, rods, cam and lifters. Any of these could pour oil, but because this would require huge clearances, they would make loud noises too.

Maybe your oil pump retaining bolt came loose and the pump fell away from the distributor drive tang...I have no idea if this is possible, but it sure sounds cool.

My bet would be on a pump suction side problem, or a pump discharge piping problem. I'll bet the engine is mechanically sound, and with some minor work your stovebolt will be up and running again.

I think lots of noise would accompany any bearing or lifter failure.

Stuart

Well; the engine is 15 months old with 200 miles on a 12 month warranty. They wished me well and want me to tell them what I find. They feel no responsibility. Once I have it open and know the real problem, we may be chatting again.

If I don't get reasonable satisfaction I'll discuss their 'service' with ALL my friends.

Are you running any type of oil filter? If so, pull the filter element, cut it apart, and spread the accordion-pleated paper out, looking for bits & pieces of metal. If there's no big chunks, you're probably dealing with a pump failure (VERY rare) or a stuck pressure relief valve. If it didn't make any expensive noises as the pressure dropped, it's not likely you've done any major damage.

The glued-on pan speaks volumes about the quality of the rebuild, none of it good. It's easy for a chunk of RTV to get dislodged inside the pan, and find its way into the oil pressure relief valve. If it gets that far, it's also possible some sealer has found its way into other oil passages, so there could be further problems down the road unless you do a complete teardown and use a rifle brush through all the oil passages, followed by lots of compressed air.

Start your inspection with the oil filter element, and also strain the oil you drain out of it through a funnel with a coffee filter in it. If you get bits of cured gasket sealer, or metal shavings, do a complete teardown and inspection, including a detail cleaning of all the oil galleries, particularly the ones in the crankshaft.
Jerry

I have seen silicone blobs kill plenty of engines.

No oil filter. I pumped some of the oil in a glass jar and looked for specs. The oil looks good to me. I'll try the coffee filter idea.

The engine is out but I haven't dropped the pan yet. Things to note:

1. The top end appears to have been oiling ok. It's all wet with oil.
2. There was no oil laying in the top of the head. Looks like the oil was draining ok.
3. Interestingly, there is some oil in the antifreeze. It's not much but it's floating in the bucket.

I'll take the pan off Monday AM and see what we have.

I'm back with an update:

I pulled two rod bearing caps and a main. She's tore up pretty good. Why?

This thing has less than 200 miles on it. The oil is clear and clean. I ran about 20 oz through a coffee filter and there was nothing in it.

The shop only cut the crank .010 so I think there's room to turn it again. We'll see if I can get the shop to at least cover the cost of the machine work and bearings (they have their own shop.)

I have no idea how to test the oil pump. Any ideas? I took it apart and it looks like it's fine. It was suppose to be new. The slot between the pump and distributor is fine.

What should I be looking at as the cause? I'd hate to turn that crank and put it back in just to have this happen again.

What are your thoughts?

Thanks.

This is just as guess, Jerry,

Leaking head gasket? Have you pulled the head?

Tim

not yet. there's nothing in the oil though.

Make sure the pressure relief valve in the pump has not gotten stuck in the open position. All it takes is as tiny piece of debris between the relief valve plunger and the pump housing to make it stick, and most of the oil just pumps right back into the oil pan without going to the bearings. Also, it's wise to take all the plugs out of the oil passages, and run a gun cleaning brush through every one.

Is the damage limited to one set of rod bearings, possibly supplied by the same main bearing, or is the damage pretty uniformly distributed among all the bearings? Sometimes a single passageway can get clogged, resulting in one main and a couple of rods getting most of the damage. Just assume everything is wrong until you prove beyond a doubt that it's right.
Jerry

I pulled the 2nd and 5th rod bearing cap and both had about the same level of damage. I think .010 cut would fix these. I pulled the third (from front) main cap and it is trashed.

What does the pressure relief valve look like? I'm seeing a spring loaded rod. I can seen through the end of the oil pump into the spring. I can see the rod through holes in the housing above where the gears are. I can see that the valve has the hole closed off right now.

That spring is usually retained by a pin driven through the pump housing. Tap the pin out, and slide the spring and plunger out. The plunger should slide freely in and out of the bore, with no hangups. Look for any debris in the bore, as well as any scratches or dings on the plunger. As oil pressure bears against the end of the plunger, it will compress the spring until a relief port is uncovered. Any excess volume of oil will be vented back into the oil pan. If a piece of trash gets wedged between the plunger and the relief port, the pressure will drop dramatically, starving the bearings. That sounds like what happened in your situation. Was the pump new with the rebuild, or was it re-used? I prefer to use a new pump whenever possible.
Jerry

Thanks. I'll check that.

Funny thing about this situation is that the oil pressure dropped to zero. There's no doubt that the bearings are bad but I don't know why they wouldn't be holding pressure.

I just went back to the oil. It looks clean (nothing showed up in a coffee filter) but seems really thin. I see some oil in the antifreeze but not much. The bottom of the oil pan has some sludge in it (thin layer) that seems to have metal in it. It's a bit creamy making me wonder if there is some antifreeze in it.

Thoughts?

The fact an engine develops any oil pressure at all indicates the bearings are getting more oil than they need. If oil was being supplied to the bearings at exactly the rate it leaks away, the pressure would be zero. When a bearing has excessive clearance due to wear, scoring, wrong size bearings, etc., the oil runs off faster than the pump can supply it, so pressure drops to nothing. With proper bearing clearance, and an adequate-volume pump, the bearings get lubed, and the excess oil trying to force itself into the oil passages causes the pressure to rise. If pressure goes above the relief valve setting, the excess is dumped back into the pan before it reaches the oil system, and pressure is controlled by the relief valve. Most oil pumps are capable of flowing at least twice the volume the engine needs for lubrication. As oil thins and clearances increase due to heat, the pressure drops due to quicker runoff.
Jerry

Can you turn the oil pump with an electric drill to check the pressure? If you could do this while in the engine and see what you have, I would think it would give you some useful information.

Good news. I showed up at the shop this morning with parts and a jar of oil out of the engine. I spoke to one of the family members and he was eager to make things right. I dropped the engine off today and hope to hear next week when I can pick it up. They have a significant race engine shop that looked at the bearings. They felt like there was a clearance issue when they assembled the engine. At this point, I'm happy that we're talking about them being responsible for the failure.

Alls well that ends well. I have had your problem but with the builder denying responsibility.