No oil pressure

[bongo666shaftsburry]

Hello, I just finished reinstalling the fixed head on my m129 engine. I cleaned the oil pan and inspected (but did not touch) the oil pump. I put in 5 quarts of oil, checked the dipstick and cranked the engine. It spun smoothly with everything moving as it should and I waited for the oil pressure to come up. It never did. I disconnected the oil pressure sender union at the gauge thinking (hoping) maybe air in the line was the problem. After cranking the engine for 10 seconds, nothing. I removed the cover off the head to see if there was oil spray coming out of the cam oil tube while cranking the engine for another 10 seconds. Again, nothing. Before removing the head the pressure was always perfect and took 3-4 seconds of cranking before the oil gauge needle was pegged. I see no oil leaks.
Any ideas?

Art

PS: Tomorrow I'm planning on sticking fiber optic camera through the oil pan discharge hole and looking to see if the oil pump spins during cranking. Also, I will remove oil filter housing to see if any oil gets that far. But then what?

[ja17]

Most likely, you have not cranked it enough. Filling the oil canister, cooler and the lines takes some cranking.   I would add at least one more quart of oil. Remove all the spark plugs so it spins over faster.

If not successful, unscrew the tachometer cable at the head. Watch to see if the shaft is turning when someone cranks the engine. This shaft/timing gear assembly also turns the oil pump. Search up some information on "vertical timing gear" to see the whole picture.  If the thrust bushing wears enough, the timing gear can move upward enough to come dis-connected from the oil pump !  Follow the instructions on how to check the up-down free play in the vertical timing gear. Hopefully it just needs a bit more cranking, the additional oil will help it prime up faster.

You may want to check the up/down free-play in the timing gear even if your oil pressure returns. Keep us up-to-date. Ask questions as needed.

[GGR]

I second Joe's comment. Priming an engine after a rebuild or after being completely empty for a while will take some cranking. You may want to oil the cams on the camshafts, and spray some WD40 in the cylinders. Then crank the engine without the spark plugs without stopping until you see oil coming out of the camshaft oiling tube on top.

[bongo666shaftsburry]

Well, there is good news and there is bad news. The dipstick showed a deficit of only 1/2 quart but I added almost 1 1/2 quarts and the dipstick showed exactly max level. After 30 seconds of cranking and no oil flow I thought I would get a heart attack but I kept on it. At 36 seconds oil started to come out of the little pipe that connects to the oil gauge and then I saw it spritzing from the cam oiler tube. Great!
But now I have another issue. Oil on #1 and #5 plugs.  I never had oil fouling issues before taking the head of. I did squirt maybe .25 oz of WD 40 in each cylinder before cranking. Rest of the plugs were dry after the first (difficult) start. 1&5 have been cleaned of oil about 20 times and the engine run (with interruptions for cleaning) for total of about 15 minutes yesterday and 15 minutes today. Needless to say it's running on only 4 cylinders. The oil on the plugs does not appear to be WD40 but the real thing.  The head was in for minor crack and spark plug hole (#5) repair. It was completely rebuilt 30k ago but I did install new seals. Could be the seals but...The #5 hole had a helicoil that was sealed on one side with JB weld as some pressure got around the coil threads from drilling too deeply in one spot in order to extract the old stuck spark plug threads ( no need to comment). It worked for 4 years. When it failed I attempted to fill the weak area with brazing--several times--which did not work out too well. Long story short, some slag got into the cylinder. I vacuumed, blew air and used magnets but don't know if I got every last bit out. When I removed the head there were some light scratches on the walls. So the oil could be from damaged walls. But I'm a bit mystified that #1 also has oil but no damage or history of oil fouling the plugs.
Any ideas?
Is there a way to determine if the oil is coming from the top or the bottom?

[ja17]

First take a flashlight and inspect the seals for the intake guides on those two problems cylinders.  They may have slipped off. 

[bongo666shaftsburry]

I was finally able to take a look at the seals on the leaky cylinders. In fact, I replaced them all. On #5 the seals seemed to be properly installed so I do not know why there was an oil leak there. I guess I will have to wait for a restart to see if the leak reoccurs or not. On #1 the intake valve seal seemed to be fine bur the exhaust valve was another story. I had hell of a time removing the valve keepers. When I finally pried out the second keeper there was a surprise waiting for me--another keeper popped out from underneath. Then, when I removed the spring a fourth keeper fell out. How I managed to force two sets of keepers in there is beyond me. The top of the seal was chewed up. When I pulled it off there were two separate areas where the valve guide was damaged. One area appears to have damage only on the outer edge. The second spot is a bit more complicated: the very edge of the inner lip actually seems smooth but pushed in a fraction making it out of round. If I can manage to attach some pictures you will see some shots with the valve all the way up and either intentionally pushed back or pushed forward (into the damaged lip) so you can get the sense of the decrease in the size of the gap ( I was able to squeeze in a piece of feeler gauge 0.0015" I between) as well as the exact nature of its irregularity. There are also a few pictures with the valve pushed down for different perspective. Unbelivably, the valve stem itself shows no signs of damage whatsoever. So.....I know I need to clean the outside burrs on the guide so the new seal does not get damaged during installation. But what should I do about the indented inner lip? Push it out (using something plastic, presumably). Sand it out (and try to keep all the sand-off from falling into the guide (but blow the whole thing off thoroughly with compressed air and vacuum out the cylinder afterward)?
Any thoughts (besides laughter)?

[bongo666shaftsburry]

Pics

[ja17]

I don't think that will be a problem. Who assembled the rebuilt head?

[bongo666shaftsburry]

Well, I did. First time. Had to try it sometime. Although I played with M130 head I have sitting around for some practice first. When you say you don't think it will be a problem do you mean I should leave that inner lip alone or should I try one of the repair mentioned methods?

[ja17]

I would just assemble it. The valve stem keeps the deformation on the inside, in check.

Lessons best learned are sometimes those which have to be repeated !  Don't get discouraged!

[Benz Dr.]

I think you should pull the head and start over. Considering the amount of problems you've discovered, I would expect it to never work right. You may also have problems with worn valve guides due to improper rocker geometry.

PM me for more details.

[bongo666shaftsburry]

pics, explanation to follow

[bongo666shaftsburry]

Ok. So, this is going to take some time to explain.  First, a reply to Dr. Benz: I may not have been entirely clear but the head was checked and fixed by a machine shop (they do contract work for Delta Airlines so hopefully they know what they are doing). However, I did the stripping and the reassembly (the head was completely rebuilt about 20K miles ago).  My guess is that pic#3 (cylinder #5) shows the result of driving 5K with improperly aligned spark plug helicoil affixed with JB weld.  I'll return to pic#3 later.
After reinstalling the seals the car run quite rough with plenty of soot on the plugs. It took me only 45 minutes to realize I switched wires for #1 and #5. After that it run pretty well with oil eventually burning off, with the following caveats:

1) Plugs look pretty clean except for #5 which is sooty. Is it, perhaps, increased cylinder volume due to damage along the edge seen in pic#3, changing fuel/air mixture?

2) Is the said damage likely to get worse? Right now the fire ring on the gasket overlaps the cylinder edge by maybe 1mm, if that. If the seal there fails would a copper gasket be an option ( I read something about copper gasket on Australian Benz site few years ago)?

3) Mistakenly, I cold torqued the head to the 280 spec of 60 ft-lbs rather than 40. Is that a problem? Should I just go on ahead and retorque the head as described in the retorque write-up on this site (starting with loosening each bolt in turn before torquing it to 65lbs)?

4) compression test: A) During first start up I did a quick compression test (engine was maybe at 120F, throttle closed, etc).  #6 ~160psi but it droped 50 psi in <15 seconds and another 20psi in additional 20 seconds. #1 dropped from 180 to 140 in 15 sec then another 30 in 30 seconds. #5 dropped over about 1 minute from 150 to 110. I got  two similar readings on each of those. I was rather perturbed by this but on the second day I did a proper test and none of the cylinders dropped by more than 5 psi. Therefore, I suspect (hope) that the de-pressurization is of no significance but I am curious about the explanation for this.
B) The proper test (I even re-warmed the engine after every other cylinder, took about 20 readings per each in three separate passes, repeated a few times with an older gauge (got consistently ~10 psi less on max readings): On first crank all cylinders were 90-100psi. Max (average)
front to back: 195-180-170-170-160(#5)-190.  From what I have read it's all good except...#5, again. Not only is it the lowest but almost 20% off from the highest (that, however, seems to be pretty high (maxed out at 210 on 4 readings (with just light build up of soot on ~10% of piston (checked with fiber optic camera) from first start up misadventure)).  Could it be from increased volume (after all, air is elastic and non-linearly so; thusly, even though the increased cylinder volume will be filled with additional air the unaltered distance the piston travels should result in decreased pressure (I think) ). On the other hand, despite concerted efforts to clean the inside of the cylinder after each attempt at fixing the plug hole threads, I found 15-20 scratches concentrated on about 10% of the cylinder wall, some of which were catching my finger nail. What's the prospect for progressive damage to either rings or cylinder wall, or, both? No obvious blue smoke from the tail pipe, yet.

5) Pic#1--WTH???!!! Is that an impression of a valve in the center of the piston (#5, of course!)? OK, on start up I heard a sort of semi-audible muffled rhythmic chugging sound (reminiscent of a steam locomotive) seemingly coming from somewhere around mid-engine. My recallection of the timeline is rather vague at this point but I did not really notice it at first on the second day as it was warming up for 20 minutes. Then I drove the car for couple hundred yards and when I reopened the hood I could not tell if I was hearing its faint echo or imagining it. I listened to the top end with a stethoscope and did not hear anything but decided to take a look inside #5 with a camera. The valve clearances were to spec before I put on the second set of seals but I did not recheck afterward.  The really confusing thing is that I heard the same sound before I pulled the head. In fact, that was what finally convinced me to do it. The first time I ever noticed that sound was right after the last attempt at fixing the spark plug hole--when I had the car towed to a welding shop and in an attempt to deposit some aluminium around the helicoil in place--except there were absolutely no marks of this nature on the piston when i removed the head. I'm perplexed. Warped head? Well, it was shaved by the shop and when I measured it it was well within spec (don't remember the number).  The aforementioned wrong torque on head bolts? But then it's only #5 with this issue. What else? And the bright slash/strike mark right in the center looks even worse. Do I dare ask about the rod bearing? Problem #5 is, clearly, of greatest urgency. I'll check valve clearance tomorrow. Should I be even retorquing the head (especially to 65lbs); running the engine (given that the noise seems to have subsided (I think))?

Well, I apologize for the length but maybe at least the pictures are entertaining.

Thanks,
Art

[bongo666shaftsburry]

 Addendum: Taking a closer look at pic#2 I think I discern an annular impression in the center of the piston after pulling the head. It's possible it became as clearly defined as seen in the post assembly photo upon being semi-cleaned and I just did not notice.  Still, the noise was there before I pulled the head and, in any case,  there is the bright slash mark in its center and, of course, the strange new noise itself.

[ja17]

Hello Art,

Sounds like you may have some issues happening. First of all, the MB literature specs 65 ft/lbs (9mkp)torque for the M129 engine warm (Tech Data Book p.94 see footnote #13). Your early compression readings seem to indicate a faulty compression tester. They fail often, carbon gets stuck in the mechanism.  Your latest readings indicate a head that was warped badly and milled flat. Note the very high compression readings on the end cylinders. During the milling process the head and combustion chambers on the end become smaller as the head is cut. I would suspect that your head may even be over-cut under factory minimum thickness?  Do you have a measurement?  This could be causing the light valve impression and noise. Double check your valve timing, which could also cause the same.

The compression reading on #5 by itself is ok, but the wide range is a problem. A smooth running engine depends on balanced and uniform compression.  Trying to set the ignition timing for a engine with very high compression on some cylinders and much lower on others is a problem. You could actually have engine pre-ignition going on in the high cylinders while the lower cylinders are fine. Fuel octane may  be a problem as you have a couple of cylinders which have very high compression while some are close to stock.

The scrapes in #5 cylinder could just be from foreign debris or could be more serious a broken piston ring. Oil consumption and oil deposits on the #5 spark plug could be clues.

In regards to a rod bearing problem....... I would remove the oil filter and break it open.  Look in the pleats of the paper. If a rod bearing is failing you will find copper particles.  You might also remove the oil pan drain plug and feel around in the bottom of the oil pan for the same.

[bongo666shaftsburry]

I was able to check a couple of things.  Measuring the head was difficult because of all the stuff in the way and the head gasket always getting in the way but  it looks like both ends are 84.1, the area by #s1&6~8.2-8.25 and #s2-5~8.3-8.35.  The intake lobes on 5&6 were straight up so I did a quick check on both of them and both had a clearance of easy 0.004 (didn't bother to check further as the head has to be retorqued first anyway).
Most importantly I think I isolated #6--by pulling off the wire-- as the "chugging noise" culprit.

[ja17]

Hello 84mm thickness is ok.  I would check the oil filter ASAP.   While your in there, make sure that the upper rubber seal is on the neck of the receiver part on the aluminum casting on the engine block. The fact that the noise goes away when one spark plug is removed is a big concern. Check the oil filter for copper flakes.

[bongo666shaftsburry]

Had no time to look at the oil filter yet but last night I took a few photos of the inside of #6 with rather disturbing results. I saw what looked like small bright metallic balls on top of the piston with a large dark surrounding ring. In the dark the spark plug looked OK but I'll have to do closer inspection with magnifying glass later today and maybe try and retrieve one of those particles from inside the cylinder. Any idea what's going on?
Thanks,
Art

[bongo666shaftsburry]

I removed the oil filter housing and ended up pulling the oil pan.  I did not find too much metal in the filter but I did find plenty of metal flakes in the oil pan; 99% was the size of very fine sand or smaller--maybe 0.25 mm and smaller--with occasional 0.5-1mm and a few ~2mm flakes.  Most looked silver  so I can't say there was any copper. Rod bearing? If so, assuming for a second the crankshaft isn't yet damaged, can I replace the damaged bearing? What might be invoved in that?
Meanwhile, I'll take the block and the crank of my m130 to the machine shop and have them looked over. The engine run fine before I pulled it except for lowish compression on #4 which, when I pulled the head off, proved to have a loose valve guide. The main worry I have is that I let the cylinders collect some not so light rust while contemplating a rebuild and a swap. It took several weeks of various soak concoctions before I was able to free up the pistons. So I don't know if it will need to be re-bored or for that matter if it can be re-bored, not to mention the expense of the whole operation. On the other hand, most of the main and rod bearings looked like new. I don't suppose one can swap in the crank from m130 into m129?

[bongo666shaftsburry]

I took a closer look In better light and I found quite a bit of  tiny cooper flakes. Should I remove the bearings I can access through the oil pan area to see how those look before I invest time into removing the crankcase to inspect #5. Am I deluding myself there is any hope of anything less than a complete rebuild?

[ja17]

Copper flakes are usually a sign of bearing damage and not just casual wear.  The crankshaft is almost always damaged at this point also.  Check the screen in the oil pump to see if it is full of metal flakes also. The screen is removable after the big snap ring is removed. At this point I would remove some bearing caps for inspection. What are your options?

[bongo666shaftsburry]

The screen did not have any metal or any other gunk on it. I removed the second main bearing and it looks perfectly smooth as does the journal. That's the good news. The bad news is one of the bolts stripped the threads in the block on its way out.