ZERO oil pressure??!?!!?!! - PeachParts Mercedes-Benz Forum

babyjames · #1 09-16-2011, 05:35 PM

I've suspected the (in)accuracy of the uro sending unit for a while now, so I wasn't TOTALLY freaked when I glanced at the instrument cluster yesterday and saw the needle on the oil pressure gauge resting on the peg at the bottom. The car was running fine otherwise, and I wasn't too far from the barn so I drove it home.

Pulled the w/s washer reservoir and got a jumper on the post on the sender. Ohm meter verified output. This is where I start thinking oil pump, or piston-cooling jets - ya' know, pull-the-engine type stuff? Maybe look into a reman, 'cause it still has a 14 head. What about that engine in AK? I have some friends of friends in Anchorage. Yeah.

Harbor Freight 94989, I believe he is. Oil pressure tester. $25 well spent. Getting the sender out and the hose/fittings for the tester gauge on do require considerable patience, and smaller hands would have helped a bit. Believe it or not, a couple of the wrenches from an MB tool kit are pretty spot-on for this job! Nice and short.

O.k., long story short, 5 bar at startup, 1.8 at warm idle. Time to get me a VDO sending unit. Lesson learned!

Cheers!
Jay

LandYaghtLover · #2 09-16-2011, 05:40 PM

I try to avoid anything URO brand. I thought some of the claims where just over sensitive folk complaining, but each complaint is real.

I am not kidding when I say that every URO part on my car, and I have had it just a year, has been re-replaced with the old/worn factory part I kept, a new part or the part needs replacing soon since its already shot. They cant even make a vacuum tube last!!! All of my intake rubber is back to stock since it was all I had on hand. All the new URO stuff collapsed and cracked in just a couple months.

charmalu · #3 09-16-2011, 05:54 PM

That`s scarry when the needle starts dropping, at least it was an easy fix.

Here is another Uro part fail.
http://www.peachparts.com/shopforum/showpost.php?p=2792345&postcount=5

Charlie

bluebird · #4 09-17-2011, 05:01 PM

I recently had a similar "0" oil pressure running down the local city street 25MPH and shut the engine off, pulled off the road into a parking lot, opened the hood. Looked at the engine could see nothing wrong from the top or from under the car. Went back started the engine, unscrewed the oil filler cap and watched what was going on in the engine, and put the cap back on and turned it off. Mistakenly I shoved my hand down behind the oil filter housing to check to see if the wire had come off the sending unit nope but Oh my God that housing was hot and I couldn't get my arm wrist and hand out quickly enough before it burned the F*** out of my wrist. I drove home after that Because I knew that I Really had oil pressure from looking in the valve cover. On my 84 300Sd I have an electrical sending unit and guage. I tested the sending unit and it was bad so ordered another replaced the bad one and tested the system by starting the engine - no good. Pulled out the instrument cluster and resoldered all the connections which were dull gray to a nice shiney silver put to back in 3 bar on startup. So the conclusion to this story is:

Stop Look Listen and make an educated decision on what to do after all its your car and your wallet.

t walgamuth · #5 09-17-2011, 05:22 PM

That is what I would have done.

libbybapa · #6 09-17-2011, 06:51 PM

I understand how you can see oil flow, but how do you see oil pressure?

t walgamuth · #7 09-17-2011, 07:01 PM

If the oil pump were broken the cam area would be dry. The main bearings get the oil first, the cam last.

layback40 · #8 09-17-2011, 08:25 PM

Quote:

Originally Posted by libbybapa

I understand how you can see oil flow, but how do you see oil pressure?

Good question !!!

I guess its fair to say without pressure you wont have flow. If you have flow there must be some pressure. Its not the pressure that keeps the bearings apart, its the presence of the oil film.

The turbo 617 has a chain drive oil pump. if that breaks there is no pressure or flow, the oil soon drains away from critical components & damage is then done. There was a thread some time ago where whunter showed the insides of a motor that had been run for an extended time (days if IRC correctly)with a failed oil pump. It was not a pretty site.
In the case of this thread the motor is a 60X, it has its weaknesses, but the comments are still valid.
Its fair to say that if you have a reliable oil pressure gauge & you see the pressure dropping (long before it is at zero), best stop & investigate. In the OP's case it was clear that he knew he had a faulty sender & all other vital signs were good so he used good sound judgement & practical experience to decide to continue. This may not have been the text book approach & so earned him some strong responses from those who appear to base their opinion on what is written in a manual.

As a teenager I used to have old cars as beaters on the farm, I remember one that the oil pressure warning light would never go out. It was a gasser though. We put a gauge on it & could only see the needle move a little when it was cold. it never seized though. There was plenty of oil going every where, just the clearances were that great that it didnt hold much pressure.

layback40 · #9 09-17-2011, 08:32 PM

Quote:

Originally Posted by t walgamuth

If the oil pump were broken the cam area would be dry. The main bearings get the oil first, the cam last.

Yes very valid point, & when the pump is no longer pumping, for a short time the oil in the galleries drains out via the lowest bearings ~ mains & rod bearings. Hence vstech's comment about noisy hydraulic lifters when oil pressure is lost.

libbybapa · #10 09-18-2011, 04:14 PM

Quote:

Originally Posted by layback40

Good question !!!

I guess its fair to say without pressure you wont have flow. If you have flow there must be some pressure.

Actually in most cases of more flow the pressure is lower. With excessive bearing clearances the flow of oil out of those excessive clearances is greatest and yet that is what sometimes resultants low or zero oil pressure.

whunter · #11 09-18-2011, 05:12 PM

After discussion with "vstech" this thread has been heavily edited.

Keep it technical, and leave the personal attacks/attitude/sniping for Open Discussion.

13. Subversion or disruption of the normal flow and/or display of the Shop Forum is forbidden. This includes, but is not limited to, wholesale deletion of prior posts and posting a new thread for the express purpose of criticism of a moderator's decision.

Brian Carlton · #12 09-18-2011, 06:07 PM

There was no "subversion or disruption" of the shop forum.

It was simply your choice (and not John) to do a wholesale deletion of this thread because it didn't suit your interpretation of the shop forum rules.

This isn't even your forum, and yet, you intercede in it whenever your see fit.

Nothing has changed.

vstech · #13 09-18-2011, 09:49 PM

actually, if I had time *(due to my excessive issues with the city and my hoarding tendencies...) I'd have done very similar to the thread. Roy called me and asked what should be done with the thread. I agreed that the posts were migrating to OD territory and deleting to better organize would be best.
I'm thankful for the assistance!

layback40 · #14 09-19-2011, 07:12 AM

Quote:

Originally Posted by vstech

actually, if I had time *(due to my excessive issues with the city and my hoarding tendencies...) I'd have done very similar to the thread. Roy called me and asked what should be done with the thread. I agreed that the posts were migrating to OD territory and deleting to better organize would be best.
I'm thankful for the assistance!

Good call Roy & John !!!!

Brian Carlton · #15 09-19-2011, 08:45 AM

Considering that most of the posts deleted were yours, your ongoing sycophantic behavior is quite obvious.

Make a note: not only doesn't it work, but it shows that you're disingenuous.