Little or NO power after bottoming out suspension- 1981 300SD - Page 16 - PeachParts Mercedes-Benz Forum

Delibes · #**226** 03-14-2013, 08:34 PM

Quick off-topic question: how dangerous is it to run around with this rubber part + strainer off the oil pump? How critical is it?

whunter · #**227** 03-14-2013, 09:41 PM

Quote:

Originally Posted by Delibes

Quick off-topic question: how dangerous is it to run around with this rubber part + strainer off the oil pump? How critical is it?

Bad idea.
Hard cornering at medium speed can expose the pickup tube = sucking air.

.

Brian Carlton · #**228** 03-14-2013, 09:51 PM

Quote:

Originally Posted by whunter

Exactly...
This is rubber.
Compress the oil pan enough, and it becomes a SEAL between the oil pickup head and oil pan face = it will vacuum seal in place, and starve the engine bearings = running metal to metal at high speed = damaging ALL bearing surfaces = increasing friction/temperature.

.

OK.........you "starve" the engine bearings for oil.

Accepted.

How do you manage to "unstarve" them and get the oil pressure back into "normal" range, which is the current situation?

If the oil pan crushed the rubber and it sealed to the pickup head, the oil pressure would not magically return after the vehicle is started the next day.

funola · #**229** 03-14-2013, 10:06 PM

Quote:

Originally Posted by Brian Carlton

OK.........you "starve" the engine bearings for oil.

Accepted.

How do you manage to "unstarve" them and get the oil pressure back into "normal" range, which is the current situation?

If the oil pan crushed the rubber and it sealed to the pickup head, the oil pressure would not magically return after the vehicle is started the next day.

I believe one of the very first thing that was done when the car was towed home (before it was started) was to replace the oil pan with a good used one. The same rubber piece was re-used. See post #1.

funola · #**230** 03-14-2013, 10:24 PM

whunter, thanks for the pic of the rubber pickup. I had no idea what it looked like. It appears there are 4 feet on the bottom of the rubber pickup to prevent a total suction seal in most instances when the oil pan is dented. How soft is the rubber by the feet? If it was made of a hard plastic (such as Nylon) I would think it would never be able to form a suction seal.

79Mercy · #**231** 03-14-2013, 10:39 PM

If the engine isnt knocking then i wouldnt think a main bearing spun, but anything is possible.

I wonder if the internal friction could be coming from the oil pump....?

funola · #**232** 03-14-2013, 10:54 PM

Maybe the bearing didn't "spun"? Judging by the design of the bottom of the pickup with the 4 feet, it wasn't totally starved of oil but partially. It ran with low oil flow and pressure for a mile at 60 to 70 mph, generating a lot of heat between the crank journals and bearings, enough to gall them and generate enough friction to eventually stall the engine.

whunter · #**233** 03-14-2013, 11:14 PM

Quote:

Originally Posted by ROLLGUY

My friend was driving his SD on a dirt road and hit a dip, bottoming out the suspension and denting the oil pan.
About a mile later, the car died.

He tried putting on new filters, but still could not get the car to start.
He got it towed home and called me.

I replaced the dented oil pan.
I also replaced the old style (leaking) primer pump thinking that is the reason it would not start.

After about an hour trying to start it, I suspected something was wrong with the injection pump.
I decided to pull the IP and replace it with a known good one.

After trying to get the start of delivery set (removing/replacing the IP three times), I figured something was wrong with the timing device, or something else.
I decided to just put the original pump back on.
After successfully getting SOD set, the engine finally started, however, it barely had any power, and it would only rev up to maybe 1,500 RPM.

I don't want to pull the IP again.
I thought that maybe the muffler was clogged, so I pulled the downpipe off the turbo, and still no power.
It seems to idle perfectly, but barely has enough power to move the car in gear (I can walk faster).

I also found out that the turbo was worn out, and thought that it might be bad enough to keep the engine from getting any air.
I removed both manifolds and the turbo, and started the engine to see if the turbo was restricting the air (had it bolted to the oil feed tube and drain tube to prevent an oil spill), but still no power.

Having ruled out he entire exhaust system, the only thing left is the fuel system.
The filters are both new, and the primer pump is new (new style).
I even tried pumping the primer while it was running to help pump fuel, but still no change.
I also tried clamping the return hose, but that did not change anything either.

Anyone have any ideas?
Like I said, I really don't want to pull the IP again.

There is the possibility that something broke inside the IP from the suspension bottoming out, but I would like to rule everything else out before trying another IP (for the second time).
I already have over 8 hours invested in trying to repair my friends car (his only transportation), and don't want to needlessly invest any more.

Thanks in advance for any ideas or help...Rich

One of the first things to fail in oil starvation is the TURBO.
It is fully spooled up, guess what happens to the turbo bearings when the oil pressure is stopped.

.

whunter · #**234** 03-14-2013, 11:31 PM

W123.123 240 D
MB# 1161860007

W123.130 300 D
MB# 1161860007

W123.133 300D Turbo
MB# 1021860007

W116.120 300SD Turbo
MB# 1021860007

W126.120 300SD Turbo
MB# 1021860007

.

JimSmith · #**235** 03-15-2013, 12:20 AM

The lack of oil pressure is a new and potentially significant piece of information. When the bearings are starved for oil, the rate of wear increases and clearances grow. When the clearances grow the oil system gains new flow paths and the overall system resistance drops, so, given the oil pump is a positive displacement type of pump, the pressure drops. Lower pressure means poorer flow through any "normal" clearances. Typically the connecting rod bearings are the ones that get oil first and establish system pressure levels. A low at temperature oil pressure reading with the engine at speed and the number one connecting rod (at least on a 16 valve 190) bearing is shot. The rest will go quickly thereafter since the pressure delivered is much lower than normal, leading to much lower flow rates, higher temperatures and so on.

But, I still don't see how 35 hp of losses can be generated without the engine seizing.

Jim

ROLLGUY · #**236** 03-15-2013, 01:00 AM

Quote:

Originally Posted by JimSmith

The lack of oil pressure is a new and potentially significant piece of information. When the bearings are starved for oil, the rate of wear increases and clearances grow. When the clearances grow the oil system gains new flow paths and the overall system resistance drops, so, given the oil pump is a positive displacement type of pump, the pressure drops. Lower pressure means poorer flow through any "normal" clearances.
Jim

I believe you "hit the nail on the head" as they say. The time that the engine has been ran since the pan was replaced, was probably enough to make the bearings worse, thereby causing the lower oil pressure. If the engine was ran very much more, I believe it would seize. By not knowing the problem was with internal friction, the engine was ran more than it should have to be able to save the bottom end. I doubt it would be worth the $ spent to replace the crank and bearings on this engine. Like I said, the car will probably live on in separate parts as an "organ donor".

JimSmith · #**237** 03-15-2013, 01:51 AM

Not having done this job on a 617 I may very well be wrong regarding doing this job, but, I have done it on a 16 valve 190 and it wasn't that big a deal. The 190 had the same oil pressure behavior along with a mess of other issues. Addressing the bearings was relatively easy compared to removing the front cover....

If you intend to pull the engine replacing the bearings is significantly easier. But it involves removing the "upper" oil pan or the bit between the block and the "lower oil pan" or the item you have removed once. It was difficult to do this with the 190 engine in the car, but it could be managed.

In general the bearing shells are faced with a softer material to make them sacrificial, at least compared to the crankshaft. On the 190, the car was driven a few thousand miles with the low oil pressure condition - no effect on power but, as noted, there were other items that involved tearing into the engine and bearing replacement was just part of the task in the end. The point is, even after a few thousand miles with the same low oil pressure phenomenon the 190 crankshaft was fine - repairing the problem was confined to replacing the connecting rod bearing shells. The vehicle has had another 45k miles on her since the repair and, like all old cars with 200k plus miles it demands some attention now and then, we have never had to go back into the front cover, the cylinder head or the connecting rod or main bearings again.

So, I would mine my way into the connecting rod bearings and take a look at the crank journals before writing the engine off. Those TurboDiesel 617's have nitrided journals which should have helped resist damage.

Good luck,

Jim

whunter · #**238** 03-15-2013, 03:54 AM

Quote:

Originally Posted by JimSmith

The lack of oil pressure is a new and potentially significant piece of information. When the bearings are starved for oil, the rate of wear increases and clearances grow. When the clearances grow the oil system gains new flow paths and the overall system resistance drops, so, given the oil pump is a positive displacement type of pump, the pressure drops. Lower pressure means poorer flow through any "normal" clearances. Typically the connecting rod bearings are the ones that get oil first and establish system pressure levels. A low at temperature oil pressure reading with the engine at speed and the number one connecting rod (at least on a 16 valve 190) bearing is shot. The rest will go quickly thereafter since the pressure delivered is much lower than normal, leading to much lower flow rates, higher temperatures and so on.

But, I still don't see how 35 hp of losses can be generated without the engine seizing.

Jim

It is a nasty race between galling, extrusion, and seizing.

Typically, due to swelling/distortion all three are trying to occur at the same time.

Oil starvation can be difficult to diagnose, until it is to late.

The only thing that might have saved him is a screaming Low oil pressure alarm.
Low oil pressure alarm.

.

Silber Adler · #**239** 03-15-2013, 08:41 AM

What I have learned from this thread is that I really need to make a skid plate under the engine sump. Skid Plate? 300D

ROLLGUY · #**240** 03-15-2013, 10:40 AM

Quote:

Originally Posted by Silber Adler

What I have learned from this thread is that I really need to make a skid plate under the engine sump. Skid Plate? 300D

Before I put the 18" wheels on my 300SD (126), I had 14" bundt wheels. There is a couple dips in the road I take often, and I hit one fast enough to bottom out the suspension. It was nowhere near as bad as Brad's car, as it just ground down the drain bolt just enough to cause a leak. Since getting the larger wheels, it has not scraped the oil pan when going over the dip in the road. However, it did cause the tire to scrape the fender lip (that is a whole other thread!)....Rich

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