m127: No oil pressure

[pagodarune]

Hello. I have a 1966 230SL, and I was going to take the last drive for the year when I discovered that there was no oil pressure at all. The engine ran for 10-15s before I turned off the ignition. Earlier the oil pressure gauge has always gone straight up and stayed there. I need some help troubleshooting. What can cause the oil pressure to disappear from one week to another while the car has not been used?

Rune R

[WRe]

Hi Rune,
I would check the oil pressure gauge first, pressure line from the motor, is there oil coming, is there a leak in this line, is oil coming out of this line to the instrument cluster.
...WRe

[ja17]

Make sure you have oil in the engine. You can remove the oil filler cap and see if engine oil is circulating up to the camshaft. The cam will be dry if it is not. Most likely the vertical timing gear has failed if no oil is circulating.

[pagodarune]

I have checked that the oil level is on the max mark of the dipstick. The camshaft looks dry, even after I cranked the engine 20-30s (I had removed the coil HT lead). At the same time I had removed the hose to the oil pressure gauge, no sign of oil.
If the vertical timing gear has failed, wouldn't the distributor be stuck also? When I first discovered this problem, the engine ran for 15s, before I turned the ignition off.

Rune R

[GGR]

Sometimes on engines that did not run in a long time it takes quite some cranking before the pressure builds up to the camshaft, though you do not seem to be in that case. No oil out of the pressure gage hose is indeed worrying as it should be squirting (it's quite a mess with oil everywhere when these hoses fail).

Have a look at the diagrams on this page: http://www.sl113.org/wiki/Engine/Start

ignition distributor and oil pump have their separate shafts. So the oil pump one can fail without necessarily impacting the distributor.

[ja17]

When the bushing over the vertical timing gear becomes worn enough, the gear rises and disconnects from the oil pump. The engine keeps running even though the oil pump stops pumping. Disconnect the tachometer cable at the engine and see how much up and down movement you have in the vertical timing gear. Search up "vertical timing gear" for more insight on the situation.

You can also remove the small oil pan from below and check to see if the intake of the oil pump is pugged up, broken etc. Check your oil pan to see if it has some road damage. 

[WRe]

Hi,
maybe this thread can help you: http://sl113.com/forums/index.php?topic=3097.
...WRe

[pagodarune]

Today I have measured the endplay of the vertical timing gear. The play is 1.8mm, which I understand is way too much. So I will have to address this. Before I do that, I will remove the small oil pan and check the oil pump. Unfortunately, I will not have the time to do this before the weekend.

Rune R

[pagodarune]

I have now removed the small oil pan. The oil pump strainer is clean, and so is the oil pan plug. Everything is looking ok. Is there a method to check if the oil pump shaft is still connected to the vertical timing gear and rotating, without disassembling it?

Rune R

[pagodarune]

The culprit is now found, the oil pump axle is broken. I guess the engine will have to be rebuilt, but before I decide on that, I wonder if there is anything I can do to determine the extent of damage?

Rune R

[GGR]

If your engine only ran 10 to 15 seconds without oil pressure as per your first post it may not be damaged. I would repair the oil pump, start the engine and see how it runs. If nothing is knocking and the oil pressure is good I would take the compressions for good measure. You can also check the lobes of the camshaft on cylinder 1 as this is the first place that gets starved. Try also to diagnose why the shafts broke. You don't want the new one to do the same.

[pagodarune]

I inspected the camshaft, and I believe that the cylinder 1 has been starved of oil. Cylinder 1 shows signs of wear, while cylinder 4 shows no sign of wear, see attached pictures.

Rune R

[stickandrudderman]

Oh dear, I'm afraid that is not looking at all good. I doubt very much that all of that damage has been caused by only 15 seconds of running.

[pagodarune]

My only guess is that the oil pump broke on my last trip, and I did not notice the missing oil pressure before I started the engine the week after.

Rune R

[GGR]

That doesn't look very good indeed.

That grey powder most likely comes from the aluminum camshaft towers that have been ground by the camshaft running dry into them. I guess professionals like Colin, Joe or Dan will chime in. The best way to do it is to take the engine apart and check and repair as required. But given that you have nothing to loose, the other option is to repair the oil pump, start the engine and see how it runs. With a bit of luck your only damage is with the towers. Knocking, grinding noises and oil pressure and compressions will tel you where you are at.

[ctaylor738]

Hmm.  I just had a sort-of similar experience with a 250.  The timing chain broke at 4000 rpm.  It destroyed the cam, two towers, and damaged all the sprockets, plus the oil pump/tach drive.  So, replaced all the gears, chain, and tensioner to the tune of $4000.  A week later, the car was back with a rod knock, and I am now finishing up installing a rebuilt short block.

Hope to spare you this frustration.   You might get very lucky, but the odds are that the bottom end has sustained damage that will show up sooner rather than later.

[GGR]

While you're with the oil pump out you can undo the lower rod bearings that are accessible and see what's the condition.

[Benz Dr.]

What you have is a blown engine. Once something breaks or a bearing lets go, it sends small shards of metal all through the engine and these small pieces go everywhere and get into everything. Special care should be taken to clean oil coolers during your rebuild or you might rebuild again, and, you will definitely have to rebuild this engine. 

[pagodarune]

During Christmas holidays, I removed one rod bearing, and it looked fine.

I have however decided to rebuild the engine to be on the safe side, and have started to remove the engine. Radiator is out, and I am searching this forum and other sources for the best method for getting the engine out.

Rune R

[ja17]

I like to remove the cylinder head first, since it is in a nice stable place to work on right now.  Next remove the engine and transmission together.

[pagodarune]

The engine is now out. I removed the top first, then used an engine hoist with an engine leveler. The engine and transmission came out without any problems.

The camshaft and front camshaft bearing is totally damaged (see picture), but I have not found any other damage.

I am in the process of dismantling the engine, preparing for a complete rebuild. What is the correct method for removing the distributor drive gear from the intermediate shaft?

[ja17]

Remove the vertical timing gear and the injection pump first. The distributor drive gear is keyed on the horizontal shaft. Once the nut and gear is removed, you must remove the woodruff key from the shaft so the spacer behind it can be removed. Next the large timing chain gear can be removed, if the timing chain is out of the way. You must now remove the 2nd woodruff key on the horizontal shaft. The horizontal timing gear can now be removed by sliding it rearward and out the injection pump opening.

[pagodarune]

Thanks Joe. Do you use a puller to remove the distributor gear? It looks as it is not enough space for a puller.

[ctaylor738]

If I recall correctly, the distributor gear slid off the shaft without much of a fight.  The sprocket was more of a challenge.

[ja17]

The camshaft bearings are the first to  suffer from lack of oil. They are the last critical close tolerance supplied by the oil pump, so they are often the first to fail. There is a slim chance that the engine damage is confined to the camshaft and cam bearings.