4 qt's low on oil, is that really bad? - PeachParts Mercedes-Benz Forum

New2MB · #1 08-02-2006, 08:56 AM

I have a 79 240D that was run 4 quarts low on oil for a short period of time. It's assumed that the oil level slowly (over a few thousand miles) got down to the point where it was 4 qt's low. The engine started making noise (presumably valves), the car was then pulled over and the 4 qt's were added. The car now runs fine but I'm wondering what was most likely damaged if anything at all.

Anyone else ever run their car that low? What happened?

Note: this isn't actually my car and I wasn't driving it so go easy on the "what are you some kind of moron" comments.

riethoven · #2 08-02-2006, 09:06 AM

My 1985 300TDt's both have a sticker inside the fuel filler hatch that says to check the oil every time you fuel.

With that said, your friend is very lucky that they did not fry the engine. If it started making strange noises then any engine component could have been damaged such as piston rings and pistons, cylinder walls, camshaft, rocker arms, crankshaft and bearings and the list goes on. More or less anything that depends on that oil for lubrication and cooling.

Teach your friend how to check the oil. It is very simple and if the car is burning lots of oil it is especially essential. It will probably burn more oil now than before, so they should also carry a gallon of oil, a funnel, a rag to clean things up, and a pair of rubber gloves if they want to insure that their hands stay clean.

Welcome to the forum, and good luck with the 240D

Endust · #3 08-02-2006, 10:13 AM

Arent you the one with the rod knock from going 4 qts low? In this post you say its fine now. Is it the same car or do you have 2 cars that both ran 4 qts low of oil??

New2MB · #4 08-02-2006, 10:18 AM

I'm guessing that pistons and rings aren't going to make much noise when the car is low on oil. I would anticipate the valves being the first thing to get starved of oil. I would also guess that with 3 quarts left in the engine the rods/crank are still getting sufficient oil. The car did not overheat so I'm guessing there wasn't excessive friction (bearings smearing across journals/pistons scoring the bores).

rrgrassi · #5 08-02-2006, 10:28 AM

If you heard any "strange noises" then, damage, no matter how slight has occurred.

New and proper oil level will cushion the damaged parts, masking the damage. When low oil level occurs, the top of the engine gets starved first. Cam bearings and lobes, valves, on down the line to pistons, rod bearings, and main bearings.

New2MB · #6 08-02-2006, 10:37 AM

Quote:

Originally Posted by Endust

Arent you the one with the rod knock from going 4 qts low? In this post you say its fine now. Is it the same car or do you have 2 cars that both ran 4 qts low of oil??

1 car. The car *supposedly* has a rod knock according to the shop (that stands to gain $3500 for a new engine) but I am in Michigan, the car is in Cali so I haven't seen it for myself (I'll get to see it this weekend).

In my other thread someone commented that being 4 qt's low shouldn't cause a problem with the rods because they would still be getting oil from the 3 qt's that are left. So now I'm wondering if anything is even wrong with this car (i.e. could it be driven for another 50k before being worked on). I've seen gas engines run very low (so low that the valves sounded like a typewriter) on oil for a period of time and after adding oil they were "fine" (no I didn't take them apart and inspect them but there was no noticeable difference in the engine performance or sounds coming from the engine) and were driven for tens of thousands of miles after that without issue.

Wes Bender · #7 08-02-2006, 10:40 AM

Quote:

Originally Posted by New2MB

I'm guessing that pistons and rings aren't going to make much noise when the car is low on oil. I would anticipate the valves being the first thing to get starved of oil. I would also guess that with 3 quarts left in the engine the rods/crank are still getting sufficient oil. The car did not overheat so I'm guessing there wasn't excessive friction (bearings smearing across journals/pistons scoring the bores).

That's an awful lot of guesswork in my opinion. If the oil level dropped low enough for the pump to start sucking some air, there isn't anything in the engine that wouldn't have possibly seen some oil starvation.

I'm with Endust. How come there was a rod knocking and now the engine runs just fine? As far as I'm concerned, that engine is suspect until proven otherwise. Buyer beware.

Good luck,
Wes

New2MB · #8 08-02-2006, 10:58 AM

Guesswork is all I can do right now. I'm compiling a list of guesses and then when I get there I will see if I can verify some guesses and cross others off my list.

The engine is definately suspect, now I'm trying to hunt down and check the most suspect components.

The engine didn't have a rod knock and then not have a rod knock.

The shop says the car has a rod knock, my sister says the car sounds and drives the same as it always has. Maybe it already had a rod knock?

Who knows, I just didn't want to interject anything that I didn't know to be true (all I really know is that it was run 4 qt's down until the engine made some noise, then oil was added, now it operates as it did prior to the low oil according to the owner).

vstech · #9 08-02-2006, 11:25 AM

Quote:

Originally Posted by New2MB

Guesswork is all I can do right now. I'm compiling a list of guesses and then when I get there I will see if I can verify some guesses and cross others off my list.

The engine is definately suspect, now I'm trying to hunt down and check the most suspect components.

The engine didn't have a rod knock and then not have a rod knock.

The shop says the car has a rod knock, my sister says the car sounds and drives the same as it always has. Maybe it already had a rod knock?

Who knows, I just didn't want to interject anything that I didn't know to be true (all I really know is that it was run 4 qt's down until the engine made some noise, then oil was added, now it operates as it did prior to the low oil according to the owner).

the "normal" diesel churn sounds very much like a rod knock. so don't be too hard on her if she can't tell a new noise from old.
if you don't trust the shop where the car is, have another shop give her a diagnostic.
a gas vehicle is much quieter and has much less stress on the parts when the oil is low. due to the diesel's masive compression ignition, low oil conditions are much more detrimental.
if there is a rod knock, driving it will certainly kill the engine.
John

rrgrassi · #10 08-02-2006, 11:27 AM

Does this shop know diesel engines backwards and fowards. I've had gasser mechanics mistake normal diesel noises for engine problems.

Cephallus · #11 08-02-2006, 11:35 AM

Quote:

Originally Posted by rrgrassi

Does this shop know diesel engines backwards and fowards. I've had gasser mechanics mistake normal diesel noises for engine problems.

How about the time a mechanic looked at my w201 with a bad timing tensioner and said, "Oh my god, it sounds like a diesel!"

Hatterasguy · #12 08-02-2006, 11:43 AM

With an old car you should check the oil once a week. Unless you have a handy idiot light on the dash that informs you if the level is low.

Mismost · #13 08-02-2006, 12:06 PM

I'm anal. I check the oil level in all our cars EVERYTIME we fuel up. I do it and I demand my wife and daughter do the same. They hate it, but they do it because I will flat come unwound if they don't...and that is not a pretty sight!

It takes all of 2 minutes and you have the time while fuel tank is filling. We have never been 4 quarts low and nobody has ever been horse-whipped...which is what I think should occur. That's harsh, but it is really harsh on an engine to run 4 quarts low on oil. You need to horse-whip somebody, get their attention, there is simply no excuse for running 4 quarts low.

#14 08-02-2006, 12:44 PM

No excuse for being 2 quarts low let alone 4!

So yes, it's really, REALLY bad not to mention dumb.

superbeast1098 · #15 08-02-2006, 12:46 PM

Quote:

Originally Posted by Cephallus

How about the time a mechanic looked at my w201 with a bad timing tensioner and said, "Oh my god, it sounds like a diesel!"

My fav is when a dealer repair tech mistook my diesel for a gaser and tried telling me that my engine was virtually dead..... That happened at a convience store/gas station..... Guy worked at some Dodge dealer a few cities over.....

I pulled up, he was coming outa the store and tells me that my engine was knocking really bad. (car was actually running rather well).... I played along with him for a minute.... I asked what he thought it might be.... He said it might have been a rod knocking....... He was "suprised" that the car still drove.....

Thats when I told him that its a diesel and I walked away.....

That dummy should not be allowed to work on cars.....

Sorry to hijack the thread.......