280 SE break in problems - low oil pressure

[wisnia07]

Hello All!

As some of you know (and helped me a lot before) I'm finishing the rebuild of 280SE engine. With the engine in car I started breaking in the engine. After first warm up (80deg, 5 minutes of running, 1100 - 1200rpms), I retorqued the head bolts. The pressure guage was pegged at engine cold and when it warmed up, the needle stayed between 2 and 3 Bar. I wasn't worried yet. I fixed all leakes and continued with the break in (full warm, 15 mins, 1500 - 2000rpm) and than the troubles started. The oil pressure guage was going down, down and dowm. I shut the engine off with 0,8 Bar at idle and maybe 2,5 Bar at 2300rpms - 20 minutes of running all together.

I took the lower sump off and it had a lot of metallic particles in it - pictures attached.

Here are some facts on the rebuild process:
- my old block was cracked, so I've sourced another one. Unfortunately it came with out the main bearing caps and I had to use the ones from the my old block. The machine shop aligned them and machined the connecting rod big ends. New shells were installed of course.
 - oil pump - I sourced a used one, but in a very good condition. It fitted in the block with too big clearance, so I made a sleeve from bronze as on the picture, to avoid pressure loos there.
- oil pressure valves - I had two sets of used valves and got the stronger ones installed (stronger with number 12 stamped on the oil pump, softer in the block).
- I changed the fuel injetion pump form 230sl R11 to correct 280sl R20 model.
- I followed the BBB, being really serious about it. Everything torqed to spec. The engine was filled and primed with special 10W40 running in oil. I also bleed the oil line at the pressure guage.

Here is what I've checked until now:
- both pressure valves - looked ok with no particles or dirt.
- got the engine out of the car to check the crankshaft bearings. All mains and connecting rod shells looked as the one on the picture. OK to me. The journals look new as well. I haven't seen the upper shells (crackshaft is still mounted) but I assume they shuld look the same as the lower ones.
- I checked the oil level in the FIP and it was quite high - around 1 inch below the rich mixture selenoid - maybe that's where the oil pressure dissapear? My old 230sl pump had a sort of valve mounted on the oil feed line (to restrict the oil flow)- my new pump doesn't have it and the oil line bolts directly on the pump housing.

I'm out of ideas and your help is very much appreciated! What can cause such low oil pressure and where did the particles in the sump came from?

Best regards,
Wisnia

 

[Tyler S]

Check the inside of the oil pump. My suspicion is with the different housing, the oil pump drive shaft may be a different length. After installing the tachometer drive, it may have jammed it into the housing and eaten up the pump case housing.

[wisnia07]

Thanks for your suggestion Tyler S. I will check it later today as I reach the garage, but honestly I doubt it's the pump's housing. It's aluminum and the flakes in the sump where more of bronze/cooper in color. I also remember to have enough play in the tachometer shaft while installing it.
I will check it anyway, and let you know.

Cheers,
Wisnia

[ja17]

You either have contamination from previous problems or failure occurring somewhere in the engine. You need to clean and check everything. Make sure your oil filter is changed and the upper housing seal is in place. Make sure your oil cooler and oil lines are not contaminated with metal. Check the #3 main bearing thrust surface. Open the oil pump and check those bronze bushings.  You can also check bearing clearances with "plasti-gauge". 

[Tyler S]

The only areas that use bronze bushings that have oil galleys in them are
IP/oil pump intermediate shaft- behind the timing gear.

Tachometer/oil pump drive shaft. Located in the block vertically below the shaft gear. 

Oil pump drive shaft in oil pump housing

[wisnia07]

Thanks Joe and Tyler S. for your hints.

I went through these components again and haven't found any recent signs of wear:
- oil pump - there is absolutely no play in the shafts in any directions, they spin freely. I didn't want open the housing yet, just to keep my first alignment after I resurfaced the top part of the housing.
- IP/tachometer shaft bushings - they have some little play and I will order them them new, but I don't believe that this is the reason of low oil pressure.

Joe I hope you are right about the contamination from previous failure - I don't know the history of the engine block, but I cleaned it the best I could (engine degreaser + high pressure water in all the oil channels, then I pumped the fresh oil through everything before engine final assembling). Maybe hot oil finished the cleaning process.

A thing which still puzzles me is the oil level in the IP. When the engine stayed over night, the level in the governor was still 4cm above the outlet hole. As I mentioned before I changed my pump from R11 to R20 with different lubrication system. What is restricting the oil flow on the newer pump? On R11 it was a valve on the oil feed line,  but on the newer it's not there.
Can this be the place where the oil pressure is disappearing?

Thanks again for your brilliant ideas!




 

[mbzse]

.../...the engine block, but I cleaned it the best I could (engine degreaser + high pressure water in all the oil channels.../...

So, you did remove the block end plugs with Allen hex in them, and routed the oil galleries (channels) out with a rifle brush&solvent?

[wisnia07]

Yes Hans, that's exactly how I did it. Because of this, I have no idea where did the particles found their shelter. I have ordered Plastiguage to check the crankshaft main bearing clearance, even though my machine shop claims they followed to book specification.

I haven't lifted the crankshaft to inspect the upper half of the main bearings (connecting rod ones looked very good).
Is there any chance that the top half-shells are 'eaten up' while the bottom ones are perfect? Maybe there was some mistake done by the machine shop while aligning the main bearing caps...

Any suggestions? 

[ja17]

Connecting rod wrist pin bushings are bronze also. Check to make sure you do not have a metal particle caught in the oil pressure relief valve, holding it open.

[wisnia07]

Checking the pressure valves was my first guess, but both of them seemed to be fine. I couldn't fine a procedure of testing them - I only compared the spring tension with the other set I have and it was identical.

I think I have to start from the beginning - I'm waiting for plasti-gauge to check the crankshaft clearances.

Regarding the wrist pin bushings - can 20 minutes of running on low oil pressure described before damage them? Still wondering where did the particles in the sump came from...

[Benz Dr.]

Low oil pressure is a result of a bearing failure but isn't the cause of it. We had an engine come in once that had good oil pressure but was making very loud rattling noises. Once I removed the crank shaft I found the problem. As it turned out, the main bearing shells were installed upside down closing off the oil galleys. This also destroyed the two outer connecting rod bearings - this was on a 190SL. Until you remove the crank how will you ever know what's going on with all of the bearings? At any rate, you have bearing ( or something similar ) shards throughout all of your engine and it should be taken apart for inspection and a detailed cleaning. I've never been able to buy a single main or crank bearing so if one is damaged you will likely have to buy a full set. Any shiny spots on any of the bearings would indicate a tight condition after such a brief operation. 

Oil pumps create volume and not pressure. Oil pressure is a result of proper clearances between the crank shaft and all the bearings as well as any other area that has a small tolerance. Since you started out with good oil pressure and it quickly dropped, you can assume that one or more of those bearing clearances is now gone as evidenced by the grit in the bottom of your oil pan. 

[Tyler S]

Have you removed the filter and dissected it?

Also the valve on the older IP's was a check valve to keep fuel from running backwards from the IP into the crankcase. these pumps have a separate reservoir for their internals. The oil feed line only lubricates the pump pistons with a very small amount of oil. Newer pumps dont use this valve and also do not have a separate reservoir and dipstick. So i dont think this is your issue but the high IP oil level should be addressed. Does it smell like fuel?

[wisnia07]

Thanks for your helpful replies!

I took the engine apart and I found the victim. The particles in the sump came from the connecting rod wrist pin bushings. Human mistake - that is my mistake. There was not enough oil on them before the engine started and they got 'grinded' down by the wrist pin. There is a noticeable play between these two elements. I believe this happened while I was cranking the engine before the first fire-up.  Lesson learned, new bushings ordered...

The low oil pressure seems to be a separate problem.
After my investigation I think it's not related with the crankshaft bearings. I used Plasti-gauge to check the clearances and they are all within the specification.  Every hole in the shells matched the ones on the block, so the problem is somewhere else. I'm just wondering about the shiny spots - Benz Dr. wrote:

Any shiny spots on any of the bearings would indicate a tight condition after such a brief operation.

Most of my bearings got some shiny spots (like in the pictured attached on top of this post). Should I be worried about it, even if the clearances are good?

For the oil pressure I'm blaming the pump itself. The sleeve I got made, didn't gave the perfect fit in the block. There is something wrong with block machined surface. The pump fitted very tight in my old block, but here it still has some clearance. I have to sort it out somehow and then check the oil pressure.

BTW Do you think I can use the same cylinder head gasket, or if once compressed I must get a new one? The head was planned and the engine run for 20 minutes only. 






                     
 

[Benz Dr.]

Spinning the engine over before starting wouldn't cause piston pin failure - something else did that. Did the holes in your bushings and the end of your connecting rods line up?

Head gaskets are a one time use. Once you crush one it has to stay crushed. Oil pumps fit tightly into the block and I bet that's where your problem lies. Small shiny spots on your bearings are probably OK if your clearances check out. Large shiny spots are a sign of clearance problems.

[wisnia07]

Thanks Benz Dr.!

I was at the my machine shop yesterday, and they also confirmed the wear on these bushings. They will fit new ones on Monday.
In fact the clearances weren't big and they said for sure: it's not where the grit in the sump came from. The reason of this failure is only me, I believe - the holes line up, but I didn't oil the pin enough. I did put oil to insert the pin, but nothing after that. The oil was swiped (while inserting the pin) and they run dry before the start-up. I did crack it for while as well.

I examined every part of the engine and none of them seemed to cause the dirt in the pan. I'm thinking now, that Joe was right in his previous reply - that must be contamination from a previous engine failure. When I received the block it was really dirty and black inside. If this failure happened let's say 20 years ago and the oil dried out together with the particles, it might have been difficult to clean it out. The color of the oil after 20 minutes of running would also confirm it - it was very dark, almost black in color. 

I think Benz Dr. is right with his bet on the oil pump fitting. If the oil while engine break-in gets very hot and thin, that should be the place of the pressure loss. I'm still not sure of the best way of fixing this problem. The sleeve on my oil pump is made to the size of a new pump, so the bore in the block must be too big. The machine shop had an idea of making two grooves (above and below the pump outlet hole) and installing it with two high temp o-rings (they stand up to 300 deg c). I'm not convinced if that's the best solution. Any suggestions here?

[450sl]

Over here there are shops that report of orig crankshaftbearingsets of poor quality.
These sets require every seperate crankbearing be ground to match the bearing in the set.

[Benz Dr.]

Thanks Benz Dr.!

I was at the my machine shop yesterday, and they also confirmed the wear on these bushings. They will fit new ones on Monday.
In fact the clearances weren't big and they said for sure: it's not where the grit in the sump came from. The reason of this failure is only me, I believe - the holes line up, but I didn't oil the pin enough. I did put oil to insert the pin, but nothing after that. The oil was swiped (while inserting the pin) and they run dry before the start-up. I did crack it for while as well.

I examined every part of the engine and none of them seemed to cause the dirt in the pan. I'm thinking now, that Joe was right in his previous reply - that must be contamination from a previous engine failure. When I received the block it was really dirty and black inside. If this failure happened let's say 20 years ago and the oil dried out together with the particles, it might have been difficult to clean it out. The color of the oil after 20 minutes of running would also confirm it - it was very dark, almost black in color. 

I think Benz Dr. is right with his bet on the oil pump fitting. If the oil while engine break-in gets very hot and thin, that should be the place of the pressure loss. I'm still not sure of the best way of fixing this problem. The sleeve on my oil pump is made to the size of a new pump, so the bore in the block must be too big. The machine shop had an idea of making two grooves (above and below the pump outlet hole) and installing it with two high temp o-rings (they stand up to 300 deg c). I'm not convinced if that's the best solution. Any suggestions here?

Did you have the block boiled out before you started your rebuild? The amount of information you give to us can point us in the right direction or way off into the weeds. I'll go with former contamination until further information points to something else. I'm holding firm that your pin bushings didn't fail due to a dry start.
Since you had all of those shards running through your engine you better think about a complete tear down and a very good cleaning with inspection after wards. I'm thinking that you may have done more damage than is easily seen right now.

[stickandrudderman]

Ditto.

[wisnia07]

I had no possibility of 'boiling out' the block. I used strong engine cleaner and I only poured boiling water wherever I could. I flushed every channel with a garden hose after that.

I have everything apart now and it here is how it looks:
1. Crankshaft journals and bearings:
- journals have no signs of wear,
- most of the bearings have little shiny spots,
- no scratches on any of the surfaces,
- clearances measured with plastigauge are within the specification.
2. Oil pump:
- housing and gears are OK,
- pump fitting into block - I can't slide it in with 0,05mm feeler gauge. It goes firmly in with a stripe of plastic film - ca. 0,03mm thick.
3. Wrist pin bushings:
- the machine shop claimed the 'old' bushings are OK and will work fine with new pins. They fitted it together and it seemed really tight while assembling.
- I will have new ones fitted now,
4. Injection pump shaft bushings.
- there is some excessive play here, so I ordered new ones as well.

I also discovered another problem which could cause the low oil pressure. I got a new oil hose made - the one on the return from the oil cooler. One of the connections has a smaller inside diameter than original. 6,5mm compared to 8,5mm. I think it was enough to restrict the oil flow.

I hope I gave enough information this time. To me the contamination was there before.  The particles running through the engine destroyed only the bronze elements - the wrist pin and IE shaft bushings. The low oil pressure was possibly resulted by the hose restricting the flow and maybe the oil pump fitting in the block.

Does the above make any sense to you? Will you make a slightly bigger sleeve on the oil pump or give it a try with 0,03mm clearance?

[ja17]

Make sure you did not leave any oil gallery plugs out.

[Benz Dr.]

What is meant by '' boiling the block '' is that it is placed into a large tank of a warmed caustic liquid for for a few hours which will remove oil and grease. After the block is removed from the tank it then needs to be completely flushed with hot water or steam to remove all traces of the cleaning solution. You can't do this with hot water at home. Any good machine shop should be able to do this for you and I would strongly suggest that you circle back and have it done. 

You still have a very good possibility that a few pieces are laying somewhere in your engine; any of which could come loose and start you on this journey all over again.

[Kevkeller]

I also discovered another problem which could cause the low oil pressure. I got a new oil hose made - the one on the return from the oil cooler. One of the connections has a smaller inside diameter than original. 6,5mm compared to 8,5mm. I think it was enough to restrict the oil flow.

If this was the reason you would have never had good pressure to begin with.

[Benz Dr.]

Oil pumps create volume and tight tolerances create pressure. Something happened to remove those tolerances and then the pressure dropped. I would suspect the oil pump after all of that crap went through it.
If I were rebuilding that engine I wouldn't put that pump back in nor would I give it a warranty without a new one. 

[Shvegel]

Listen to Dan.  He does this for a living.  When I worked in a shop in Northern Minnesota years ago the wealthiest man in town sent in his 80's Jaguar with an oil pressure problem.  The car only had 14000 miles on it. Due to errors by both Jaguar and our trusted machine shop who sent the crankshaft to the worst machine shop in town because their crank grinder was broken.   I watched the guy next to me remove, tear down, reassemble and install that engine 4 times.   

[Benz Dr.]

Listen to Dan.  He does this for a living.  When I worked in a shop in Northern Minnesota years ago the wealthiest man in town sent in his 80's Jaguar with an oil pressure problem.  The car only had 14000 miles on it. Due to errors by both Jaguar and our trusted machine shop who sent the crankshaft to the worst machine shop in town because their crank grinder was broken.   I watched the guy next to me remove, tear down, reassemble and install that engine 4 times.

Those are some very painful learning lessons. Most are, but are some of the best teachers.

I learned a long time ago that every time I try to save someone any money it usually ended up costing me even more money before I was done. There are NO short cuts when building engines.