What are the chances? Oil Bypass Valve/ Spring

[Duramax7man7 505]

So after getting the rear valve replaced in my new 1991 520h find P220G engine and getting it back together... The initial startup with new oil and filter the engine sounded really tight and quiet, component wise.

The Engine only has 1250hours on it...

 Now after running it a few times for no more than 10-15mins and mostly at idle and only a couple of minutes max at full throttle testing out the transaxle I'm noticing a quick knocking noise.

 The crank case breather is clean, spark plugs gapped correctly, carb set to factory specs and even a bit of motor honey to help quite things down I still hear this noise. It sounds like the rods. But like I said, wasn't there at the initial startup!?
The oil pressure light isn't coming on while running. BUT, could the tractor sitting in the fluctuating climates cause a weakening of the oil bypass spring and only show symptoms of being weak after the first real run and heat up of the engine after getting a new valve seat?

 I hear the knocking during running and especially when shutting it off. It's not crazy rod knock but is more than I'd like to hear from a engine with half the hours of my 1990 520h engine.  My 1990 520h P220G has almost 2400hrs on it and sounds great.
 I was hoping that this engine would sound better than my 1990 and for it's first run it did.

 

[6bg6ga 271]

•  

   

• Plastigauge - Plastic Precision Clearance Gauges

   

  PLASTIGAUGE

   

  Did you use plastigauge to check the rod to journal clearance?  Did you have an oil pressure gauge hooked up?

Edited May 18, 2017 by 6bg6ga

[Duramax7man7 505]

No. I merely did a grind procedure before sending it off to have a neat rear valve seat machined and installed. I will go this route if I need to. Planned on it with my other engine but this one may need it before. I guess it could have just been abused but I don't understand how the first run sounded great! Then consecutive runs produced the sound. I can shoot a video tomorrow and post that. But it's definitely got a light knocking which seems to be in both rods. It doesn't sound like a single cylinder knock.

[6bg6ga 271]

First of all please don't take any offense at any of my questions. Did you clean the crank oil passages? Blow them out with compressed air? Did you use some type of assembly grease when you put the engine back together? Did you fill the oil filter with oil prior to installing it? Did you pack or prime the oil pump? 

 

Its probably uncommon but not all together impossible that your pump didn't do its job. Sometimes a pump doesn't get a prime and simply doesn't pump or gets a late prime and the result is rods and mains starving for oil. I doubt that the crank has been hurt but it may have some aluminum attached to it. This can be remove by using sodium hydroxide on it and polishing it. I just finished cleaning up the rod journal on my B43 with the help of oven cleaner and a length of mule string. 

 

Now, I've seen this happen with small engines just the same as I've seen it happen with Cadillac engines. Some engines its better to follow a factory approved method to prime the pump.

 

What I would do is install a pressure gauge to see if you do have pressure. Once that is figured out take the engine down. Use plastigauge to check the rod bearing clearance. Inspect the rods for damage. I would assume the crank journals are slightly undersized. Inspect the rest of the engine and from there your choice is going to be replace the crank or replace the rods with another set that will allow you to have the rod clearance within factory specs. You may be able to have the journals turned and obtain undersized rods to mate with a .010 under crank.

Edited May 18, 2017 by 6bg6ga

[Duramax7man7 505]

I would never do so ( I don't think, ha ha) and thanks for the response either way.

 

 I did not tear the engine down. I only removed everything down to the heads, intake and exhaust and everything over those I plugged every hole I could as best I could and left the rest up to the machine shop which machines many race engines. So I can only guess that they were cleanly in their procedure. They gave the engine back very clean. I do use assembly grease when reassembling. I always fill the oil filter with oil and when I removed the oil pan for sludge removal there wasn't a lot and the oil pickup tube was clean.

 I was hoping that I would have to do this with my 1990 520h with 2400hrs before this one, but it is what it is...

 

 

 

 

[6bg6ga 271]

Ok, I waited for others to chime in but that hasn't happened as of yet.

 

Under normal circumstances the by pass spring/ valve are shut. When the valve is shut the oil is routed to the oil filter is filtered and arrives to feed the engine purified oil to the bearings, crank, cam and so forth and returns to the pan and the whole thing repeats over and over and over again. Now, I'm going to take the stance that your filter is new and so is your oil supply and the level is full. The only conclusion I can draw from this scenario is the pump failed due to possibly an internal failure or excess clearances which dropped the pressure below a good usable area.

 

If the filter were clogged, improperly made, bad internal valve and so forth the bypass valve would have opened up allowing unfiltered oil to be sent to the engine to supply the bearings and such.

 

The question if I am understanding it correctly is would a faulty bypass spring caused the failure of the engine. Its a darn good question, a hard question to answer simply because its answer is going to be pure speculation based entirely on content posted and no hands on to examine anything.

 

Here is where I am going to go.  I'm making the assumption like I said the oil filter is good and if not the bypass should have opened. If it stuck in my mind that caused the engine to fail. However having said that and knowing the oil pressure relief should open at a relatively low pressure I'm amazed it didn't open. If the spring were broken it should have resulted in the valve opening prematurely resulting in all the oil bypassing the oil filter. It is also possible the pump clearances had opened up enough that the oil pressure was insignificant to provide a reliable source of lubrication thus resulting in engine failure.

 

This is one of these things that is going to haunt you until you tear it down more and pull the pump to inspect it. I would remove the pressure relief assembly provided it comes out. Pull the pump apart and check for damage and check clearances and please do post your findings.

[6bg6ga 271]

I haven't found oil pressure specification as of yet but I'm sure there out there. What I did find was that some Onan's are equipped with a pressure switch which shuts the engine down when the pressure drops to 14 psi.  So, from that I will draw the conclusion that the engine must have at least 14 psi to be able to provide adequate lubrication. Now, having said that the pressure switch is close to the pump. If the internal bearing clearances were a bit worn the pressure would drop even lower.

 

It would be nice to know the actual oil pump specifications for future reference.

[Duramax7man7 505]

Yep. Oil pan thoroughly cleaned, new oil and new filter. 

 I thought that I read in the master manual that the spring over the valve, under the cap screw on the top of the engine is what provides the proper oil pressure. So if it potentially over compressed with the raising of the heat during the first run and didn't return to the correct length, then that very well may cause low pressure and ultimately this slight quick knock I'm hearing. The manual does mention giving it a test by compressing it with a specified and lbs and then measuring the length as well as measuring the cold length uncompressed if memory serves me correctly.

 I'm eager to open up the crack case and take a look at the pump. This was my first idea but figured I'd inquire about the oil pressure spring. I'm almost wondering if the new oil may have cleaned up the goo inside the pump a bit too much and allow the warn clearance to rear it's ugly via the knocks. I will post a quick video in a little bit of the sound....

P.S. Thanks for the brainstorming my friend. Always good to have a plan of action.

[6bg6ga 271]

Its very unfortunate that this had to happen to you. I always try to see if there is a positive side to things. In a way your unfortunate luck I believe will tend to educate others. It would be very helpful if you could post a picture of your pressure relief spring and valve as well as pictures of the pump.

 

I would pull off #2 rod cap and look for aluminum stuck to the rod journal. I don't think your going to see anything so this is a safety exercise. If there is something please do elaborate.

 

At any rate I will await your findings and maybe I can possibly be a means of help and support.

[Duramax7man7 505]

Okay, so finally here is the video I promised...
 

Let me know what ya think.
 

 

[6bg6ga 271]

My laptop speakers aren't quite capable of hi fidelity sound. I'm not hearing anything until shutdown and then it sounds like the rods are knocking. Still would like to see an oil pressure gauge to see what is happening.

 

My knowledge of the bypass spring still tells me it is seated unless an obstruction happens such as the oil filter clogging in which the bypass would open. In either case oil pressure would be maintained in the engine. What oil weight are you using? I would suggest that you drain it and go to a heavier weight oil such as a straight weight and possibly add a Teflon additive to the oil and see what happens. At any rate you will only be out two quarts of oil so the cost is low. I'm old school and still do not favor the multi blends.

 

[Duramax7man7 505]

I agree. The rods are definitely out of spec for clearance it seems. I use straight 30 weight and then used the appropriate amount of motor honey to help with knock. BUT, I did overfill the oil a bit and then drained some so I'm not sure if that fully included some of the motor honey. At any rate, wouldn't the oil pressure gauge being throwing it's light if the OP was to low? It blinks upon turning the ignition on but then goes out after the engine starts.

[6bg6ga 271]

I'll be perfectly honest with you. I don't trust idiot lights. I prefer a mechanical gauge so you have a feel for what is happening. I realize its a pain to hook up a gauge but that is going to be about the only way your going to know what you actually have for pressure.

[Duramax7man7 505]

I understand. Im sure its lower than desired if even the rods are worn..

[ericj 1,576]

I bought a 520 last summer. the seller told me the motor was junk and I couldn't get it to crank with the jump box I had with me that day. I brought it home and pushed it off the trailer and tarped it over. Back in February I pushed it into the shed and was going to replace the motor but, decided to see what was wrong with it. Got it to crank over then decided to do a compression test. it had 120 psi on both cylinder, Okay so far then got it to fire on carb cleaner.. Cleaned the carb and fuel system and got it to run. Like you said it sounded good at first but the longer I ran it the more I heard a knock, not like a rod but a knock still the same. by chance I pulled the belt guard off and then found the real problem. All the bolts holding the bearing plate on were finger loose. tightened all the bolts and now no more knock. apparently it had run long enough it had pushed the gasket out causing it to still leak oil. I bought a new gasket but haven't had a chance to replace it yet. So it could be that easy or could be the path you are going down. Good luck

 

 

 

 

 

 

 

eric j  

[6bg6ga 271]

10 hours ago, ericj said:

I bought a 520 last summer. the seller told me the motor was junk and I couldn't get it to crank with the jump box I had with me that day. I brought it home and pushed it off the trailer and tarped it over. Back in February I pushed it into the shed and was going to replace the motor but, decided to see what was wrong with it. Got it to crank over then decided to do a compression test. it had 120 psi on both cylinder, Okay so far then got it to fire on carb cleaner.. Cleaned the carb and fuel system and got it to run. Like you said it sounded good at first but the longer I ran it the more I heard a knock, not like a rod but a knock still the same. by chance I pulled the belt guard off and then found the real problem. All the bolts holding the bearing plate on were finger loose. tightened all the bolts and now no more knock. apparently it had run long enough it had pushed the gasket out causing it to still leak oil. I bought a new gasket but haven't had a chance to replace it yet. So it could be that easy or could be the path you are going down. Good luck

 

 

 

 

 

 

 

eric j  

 

I sincerely hope the posters luck would allow him to arive ame problem as you have. Unfortunately, when you listen to the video the rod knock is very pronounced when the engine is turned off which is a very typical sound when the engine is reved up and the engine is coasted. Usually a rod knock is heard under a engine coast condition or upon shut down.

[Duramax7man7 505]

Yes the engine is nice and oil free on the exterior! Glad to see that. I did get some 40w and a bottle of Lucas oil stabilizer to see how that does. The valves were adjusted so I it's not that.

[WVHillbilly520H 10,369]

Be careful with heavier weight oils, they can "blow" the seals/gaskets, my dad thought adding Lucas + 10w40 to his last truck with 5w30 requirements every change would be a good thing at 50k but by 75k the front timing cover seals and valve covers were leaking oil profusely, so keep that in mind, Jeff.

[6bg6ga 271]

10 hours ago, Mastiffman said:

Yes the engine is nice and oil free on the exterior! Glad to see that. I did get some 40w and a bottle of Lucas oil stabilizer to see how that does. The valves were adjusted so I it's not that.

 

Use the 40w first and let the oil get hot. Once hot drain some out to accommodate the stabilizer so your total doesn't exceed the oil level.

1 hour ago, WVHillbilly520H said:

Be careful with heavier weight oils, they can "blow" the seals/gaskets, my dad thought adding Lucas + 10w40 to his last truck with 5w30 requirements every change would be a good thing at 50k but by 75k the front timing cover seals and valve covers were leaking oil profusely, so keep that in mind, Jeff.

 

I'll have to heartily disagree. I ran 90 plus psi in my GTO's when I had them in the late 60's early 70's and ran straight 30 or 40 depending on the ambient temp. Never had one leaking seal or gasket. I used high pressure high volume oil pumps and then I installed a shim under the bypass spring. I was told I would also blow oil filters........nothing EVER leaked and no oil filters ever blew up.

 

Most engines will develop slight leaks in the front crank seal over time and the same with valve cover gaskets. The REAL test of how gaskets and seals stand up is when an engine is either turbo charged or supercharged. My 93 Z-28 Camaro was supercharged as I installed a Procharger D1R and was making 18PSI of intercooled boost. Pressure like supercharging is what has a tendency to make gaskets and seals leak.  None leaked in my setup.

[WVHillbilly520H 10,369]

53 minutes ago, 6bg6ga said:

 

I'll have to heartily disagree. I ran 90 plus psi in my GTO's when I had them in the late 60's early 70's and ran straight 30 or 40 depending on the ambient temp. Never had one leaking seal or gasket. I used high pressure high volume oil pumps and then I installed a shim under the bypass spring. I was told I would also blow oil filters........nothing EVER leaked and no oil filters ever blew up.

 

Most engines will develop slight leaks in the front crank seal over time and the same with valve cover gaskets. The REAL test of how gaskets and seals stand up is when an engine is either turbo charged or supercharged. My 93 Z-28 Camaro was supercharged as I installed a Procharger D1R and was making 18PSI of intercooled boost. Pressure like supercharging is what has a tendency to make gaskets and seals leak.  None leaked in my setup.

I said be careful that it could, and with "TODAY'S" tight clearances dad's old truck was a 1 owner 2002 4.3L V-6 (with the dreaded plastic covers) nary a leak until the 75,000 mile mark with the 10w40 with Lucas, I had a 2000 4.8L V-8 with close to 250,000 miles on it and was just starting to seep at the valve covers also 5w30 by factory but around 100k mark I used 10w30 high mileage Castrol GTX with the factory ACDELCO filters, therefore from that/my experience the heavier oils will eventually cause the seals/gaskets to erode, not a high performance built engine just a factory tight clearance stocker, in my 406SBC I run a high volume standard pressure oil pump it increases about 10psi/1000rpm to 80/90psi @ 8k, but again I only use 10w30 and no leaks on the old engine for the new one I hand built and clearanced 4-5 years ago and I've owned the Malibu since March '01, Jeff.

Edited June 14, 2017 by WVHillbilly520H

[6bg6ga 271]

Let me know what you turn in the 1/4 mi if you ever run the Malibu. With mostly stock suspension, stock rear and coming off the line from a dead idle I ran a 10.12@138.56 and that was spinning thru 1st and second. It finally hooked in third and I went thru the traps in 5th gear. Never got to run it again since I wouldn't put a cage in it. It was probably a low 9's car if it ever got traction. ET streets 11.5 wide at 9psi still didn't get traction but did manage to stay halfway straight

 

Mileage contributes to seal and gasket leakage was well as clearances. When bearings start to wear oil can and usually does go in different directions. My Z with the LT4 internals had some composite valve covers off the Vette engine it was derived from. They had a simple O-Ring around the outside and despite my fears it never leaked.  Oil pressure with high volume high pressure pumps can also vary especially when you blue print the pump. I'm an old racer by the way and have used many tricks over the years.

[Duramax7man7 505]

The oil volume displacement is what I did on my 1990 520h with motor honey to ensure that I wasn't overfilling the system. But thanks for mentioning it. I will post back my results with the thicker lubricant.

[WVHillbilly520H 10,369]

Just remember it's not just "pressure" that keeps an engine alive, it's the "volume" of  "clean" oil going through it to lubricate, clean, and cool it, especially with an air cooled engine, and yes a low hour/mileage engine that wasn't maintained will ruin long before a well maintained high hour/mileage engine of the same kind/brand/designed... As for 1/4 mile times we'll never know only an 1/8 mile track near by me...but if I ever get a Friday night or Saturday test tune that doesn't conflict with work or family I'll let you know, Jeff.

[Duramax7man7 505]

Okay, so I ran the engine for a couple of minutes, jacked up the tractor so that the the most oil would drain out... removed the old oil and put in 40w with 20% of the volume replaced with lucas oil stabilizer. The engine sounded okay at first, then a little better and now worse. The knock is getting louder. 

 

 But here is the odd thing... the old oil 30w with motor honey in it, which is only a few hours old has a green tint to it???

 

 Check it out... Ive never noticed this in any other engine oil change. Could there be something contaminating the oil? 

 

[6bg6ga 271]

Now is the time to check the oil pressure...... once that is done you will be 1/2 way there. Either you have good pressure and you have rod wear or the pressure/ volume is low and you have pump problems. Solve this problem first and then its  time to put the engine on the bench if the pump is good and you have good volume. I would suggest that if you have to go into the engine that you drain the oil and keep it provided you can drain it without getting dirt with it. Pull the pan and take a rod cap off and examine it and the crank. Look for any aluminum on the crank's rod journals. Look at the oil passage in the crank. If everything looks good purchase some plastigauge  and use it following its directions to determine the clearance.  Your either going to come up with excessive rod to crank clearance or the pump simply isn't putting out enough volume to lubricate properly.