Oil gauge peaks at only 2.75 when pegged - is this bad?
 

91 300E, 129K

I just noticed on my drive home today that my oil gauge peaks at 2.75 when pegged. I could have sworn that it used to go to a full 3.0, but I really don't remember. For all I know, maybe it always did this? Anyway, at idle in D, it is at about 1.0 or just slightly below and goes all the way to 2.75 pretty quickly when gas is applied, perhaps around 2500 RPM or thereabouts (I'll have to check again to be sure). Is this bad? Shouldn't it go all the way to 3.0? What damage could be caused by this lower pressure? It troubles me that there isn't a red zone either at the top or bottom of the gauge to indicate that the needle is sitting somewhere it shouldn't.

I just replaced my water pump last night, and got to thinking: could I have disturbed a wire or sensor in the process that might be contributing to this lower pressure reading? Could there be a higher resistance somewhere as a result of me jostling a connection or maybe spilling coolant on it? Where exactly is the oil pressure sending unit located?

I am hyper paranoid about damaging something by starving the engine - is this an overreaction? For the record, I am running 20W50 and don't burn a drop of oil. The engine is in perfect running condition. I just resealed the upper cam timing cover a few days ago to fix chronic seeping. I also just checked my oil level, and it is just under the high mark on the dipstick.

Any opinions please?

Thanks in advance!

I would suspect that its more likely that you have a problem with either the gauge, the sender, or the associated wires, rather than an engine problem.

A quick, and easy test you can do is to unplug the wire at the oil pressure sender unit and look at you oil pressure gauge. With the sender unit unplugged, the oil gauge should now peg at 3. If it does not, than your problem is in one of the items that I mentioned.

If it does peg at 3, than you either have a bad oil pressure sender unit, or you may indeed have a problem with the engine. I would bet on a defective sender unit however.

Phil

Thanks for the quick response! Now regarding my water pump replacement last night, is the oil pressure sender located somewhere in that vicinity (front driver's side of engine)? Could I have bumped it loose or spilled oil on the connections? Where exactly is the sender located? Thanks again in advance!

I watched the oil gauge the whole way to work today. Still pegged at about 2.75. Now here's the kicker - if I put the car in neutral and rev it really high, the pressure slowly moves up, hitting almost 3 right as the tach hits redline. Does this indicate a blockage somewhere?

I've been thinking about what I said before; I'm positive the gauge used to hit 3 before I did the water pump. I'm psycho about my gauges and always watch them as I drive around. I'm absolutely certain that I would have noticed the gauge at 2.75. So the question remains - could I have bumped something while doing the water pump that could have caused this to happen? Why would the gauge read a perfect 3 before the water pump replacement, and then only 2.75 afterwards? Could I have dripped antifreeze or oil onto an electrical connector somewhere, forming a resistance in a circuit? I don't really know how the gauge works - I'm just throwing a wild theory out there.

As a reminder, the gauge always reads steady at just below 1 when the car is hot and put in drive. Slightly higher when it's in neutral or park. Aside from the new maximum of 2.75, it seems to behave properly in every other way. I run dino 20W50 and change the oil every 3000 miles. It is always clean when it comes out.

It's going to be raining today when I get off work, and the big spring above our garage door broke last night, so the door is stuck in the down position (any suggestions on that problem are also welcome). As a result, I won't be able to troubleshoot this problem for at least the next day or so.

Help! Anyone??? I don't want to damage my engine!

It is possible you have a problem in the oiling system that won't let it build full pressure, but chances are good that it is an indicater problem. If you are really low on pressure, you have enough to not harm the engine. You didn't say how the oil gets changed. Do you do it yourself, take it to an Indie, take it to the dealer, or take it to Goofy Lube? Some of those cheap filters can cause low pressure. The problem of cheap filters and low pressure has come up in other threads. Good quality filters are still cheaper than engines.

Peter

I change the oil myself and use good oil and a good filter. But again, the part that bugs me about this problem is that the gauge was reading 3.0 before I replaced the water pump, then only 2.75 afterwards. Is it just coincidental? Could I have broken something under there? On the other hand, if my pressure really is only 2.75, will that kill my engine? Doesn't the fact that the gauge pegs pretty quickly upon accelerating mean that the oil system is healthy overall?

What brand filters and where do you buy them?

I don't see how you could have broken anything. It may have been coincidental. Check the connection at the sending unit.

As I said you appear to have enough pressure so as to not damage the engine, but you do want to correct the problem. 2.75 atmospheres is a safe enough pressure.

Peter

Fram filters from Autozone. Wait a minute, those aren't exactly great filters. Should I try changing the filter with an OEM and see if that corrects the problem? There's a dealer on the way home and I can just swing in there and pick one up. Where exactly is the sending unit located, and what is the pressure it measures? Does it measure before or after the filter?

That is exactly what I would do. Pick up a dealer filter and get that POS FRAM filter out of there. That is exactly what caused the low oil pressure on the thread I mentioned earlier. You lied to me when you said quality filter. You are new here so you missed some of the threads where people have cut these cheap filters open to find hay and all kinds of junk in them. We still don't know if this is your problem, but it can't hurt to get that filter out of there. You can buy a stock of good filters from Fast Lane on this site. It also helps support the site.

Good luck,
Peter

Actually, I read that thread you're talking about, the one where the filters had the cotton gin material and insects in them. But I recall that the OEM filters also had the same thing inside when somebody cut one of them open. It seemed the consensus from that thread was that even the OEM suppliers are manufacturing on the cheap in India or Turkey or wherever.

I just placed an order on Fastlane a few minutes ago, for hoses and intake tube I cracked under there while changing the water pump. I would have ordered the OEM filter if not for having to wait on shipping time. It might be quicker to swing by the dealer on the way home. I know they're a ripoff though; the bypass hose for the water pump cost me about $16 there; it's only $5 on Fastlane. Of course, after shipping they might be close in price and at least if I pick up from the dealer I won't have to wait several days for shipping while the engine is ripped apart...

Where is the oil sender unit located on the engine? I'd like to follow a previous poster's suggestion that I unplug the sender and see if the gauge goes to 3. Do you concur with this suggestion?

I don't remember the thread exactly, but I seem to recall that these were like Bosch filters supplied only to the cheap DIY stores. I believe the sender is on the back of the filter housing. I know being a professional and owning several of these M103 cars, I should know, but it is something I haven't dealt with. I'll look at the 91 300E when I get to the shop today.

Peter

If you disconnect the sender, it will go to ZERO!

When my sender went bad, it pegged to 3 once the ignition key was twisted to the II position.

You have a different engine configuration than mine, and on mine, it's by the rear of the oil sump on the driver's side. You have to access it from underneath the car.

I respectfully disagree. If you disconnet the sender wire it will, (or should) peg at three. If you ground the wire it will, (or should) go to Zero.

Phil

Interesting...I recall just the opposite happening when I had to deal with mine, until I replaced the offending sender...

...then again, I also had to rebuild the harness in the process as it seemed to suffer the same fate as the main wiring harness...

Contractor is scheduled to come to the house tonight - the coil spring that helps the garage door up snapped and the door is stuck shut. Somehow our door has only 1 spring, so the door can't be lifted. We are having a 2nd backup spring added to provide a limp mode in the case of another spring failure; that way at least the door can be opened manually. Hopefully he'll finish in enough time to allow me to use the garage tonight (it's raining outside).

I will try unplugging the oil pressure sender. So are we in agreement that it should go to 3 when unplugged and 0 when the wire is grounded to the chassis? And that I have to access it from underneath the car?

About the garage door spring, have you been servicing it? Everything needs to be serviced including cars, tooth brushes, mates, garage doors, and just about everything. You need to coat the spring every 6 months with a penetrating oil. This keeps the spring from rusting and binding and particularly where you live. Follow this recommendation and the spring will operate as smooth as silk.

Peter

Wow! I never knew that, except the mate part. ;)

Did you get the FRAM filter out of there? My Dad took the 190E 2.6 to a mechanic that installed a FRAM and the oil pressure would not get much above 2 bar after that. I swapped a new OE filter in, and presto, problem solved. The old thread is here...

http://www.peachparts.com/shopforum/tech-help/82489-%25-%25-%2A%24-fram-filter.html?highlight=fram

Wow, that is one interesting thread. It's funny - I have always used a Fram in my cars - now I know they're junk.

My car is due for its next oil change in about 1000 miles. From previous posts it would seem that it should be OK to drive the car with the oil gauge at 2.75 until my next oil change, at which point I will replace with an OEM filter. Can anyone else confirm that this is safe? Or should I replace it now? We're only talking a few bucks here...

Peter

You must subscribe to the Larry Bible philosophy.................Get them hot & do them often. :D

I lost 1/2 a bar at idle when I had a Fram filter in my SDL. Needless to say its stay was breif.

Again, I am surprised. But if so many people have had problems with the Fram (evidently including me at this point), then I'll never buy one again. Question: is there another major brand (i.e. Motorcraft, Delco, etc.) available at Autozone that I should use? Or should I just go to the local Foreign Car Parts store or maybe even the dealer to get a filter? I think I want to swap it out tomorrow to test this theory...

Use OE

What about Bosch? Fastlane has them for $5.22 and I know Autozone has Bosch. I was able to snag 4 Bosch filters for my SDL off ebay for about $9 each. OE's cost $12-$14.

You guys don't give up, do you? How cheap can you get? Even if you pay full boat at the dealer which amounts to about $50.00/yr for filters, how much is your engine worth to you? Some of you guys will piss away good money for synthetic oil at $6/ qt which you don't need and try to save $5 on a POS oil filter made out of garbage. Just buy them from Fastlane and have piece of mind.The onlly things I'll buy from Autozone, Kragins, or any other chain is spray paint, antifreeze, spark plugs, loctite, and such items. The rest of the stuff thors places sell is garbage. I wouldn't give a thought to putting on one of their starters or master cylinders, because I like to do things only once and move on.

P/S The above list also includes Napa stores as another chain to avoid. Hey as a gregarious professional mechanic who talks to a lot of shop owners, that is the word in the industry.

Peter

Bosch is sold by Fastlane for a 1991 300E. I have opened up several brands of filters for the 603 Bosch, Mann, Heignst, OE are all the same inside. STP is a Heignst in a blue box. MB does not make their own filter, they sub contract them out. I am pretty sure the OE filter is a Mann. I know the OE ps filter is Mann it is stamped right on it. I am not cheap I have done my research. I would run Bosch on any car without a second thought.

The question isn't to use or not to use Bosch. The question is where did you buy it and where was it made.

Peter

Just another small point to remember.
The world is flooded with counterfeit parts.
It's a HUGE problem.
When I purchase my oilfilters ( at my friendly M-B dealer), it comes in a geniune M-B box, complete with " holographic " ? seal.
Hell, it's only $ 8.00 & I KNOW what I'm getting. ;)

A Bosch oil filter for a 300E is the same whether you buy it at, Fastlane, Autozone, Walmart ect. Bosch is Bosch. If it were my car I would buy a dealer filter and a Bosch then cut them apart and compare, I bet they are the same. I have gotten a few Mann filters in the official MB box.

The oil filter thread in the diesel forum is a perfect example of this, all oil filters for 603's are junk. Some are just slightly less junk, ie dealer filter seems ever so slightly better.

Hatteras guy,
Keep smoking whatever you're smoking, and some day you'll grow up to be a Grand Banks. Manny is on the money. The dealer filter or one from Fastlane isn't that much money, and you know what you are getting. You are shooting craps with your expensive engine as the purse when you buy that garbage from chain stores. Get real. This is America. Have it made as cheap as you can, and improve that bottom line for the share holders. Quality is not important. In all fareness to some American companies that have resisted that concept, I will name a few companies that I am aware of that have been admirable in product and service. Levi Straus, Ruger Firearms, Devilbliss paint equipment, Kirsch drapery products, Manchester tanks, Delta Faucets, James Cash Penney, and I am sure there are others that I am unaware of.


Peter

All of you bring up some good points. I think I'll either pick one up from the dealer or order one from Fastlane. I need to order a set of chrome grill strips anyway...

I'll let everyone know if replacing the filter does in fact raise my maximum running oil pressure above 2.75. I have a feeling that it will...

Update on my oil pressure readings:

Max oil pressure reading continued to drop as the weeks went by; most recently the pressure would only go up to about 2.4. If I punched the gas on the highway and took the engine to about 6,000 RPM the oil pressure would nudge a little bit higher, about 2.6. At idle the reading would drop to .4 (used to be just under 1.0).

My odometer just rolled over to 130,000 and I have decided to adjust my oil change interval from 3K to 5K. I changed the oil last night using standard 20W50 oil (used Castrol GTX high mileage in the green bottle at AutoZone). But this time I went to the dealer and picked up one of their OEM filters. After driving last night and about an hour into work this morning, guess what - oil gauge is back to normal!!! Steady rock-solid reading of 3 by 1600 RPM, and just under 1 when idling in gear at a stoplight. Looks like the Fram filter was indeed the problem. I will NEVER buy a Fram again!

Just a few observations regarding the OEM filter. Cost me about $13.50 vs. $5.00 for the Fram - a pittance, considering the peace of mind it will give me. Came in the MBZ packaging with a holographic seal and all - pretty nice. Markings said it was made in France. I still have the box and can post a picture if anyone wants to see. But interestingly, the filter itself is only 1/2 the height of the Fram. I asked the service desk guy at the dealer about this. He said MBZ had recently changed the recommended filter to this one and that the old one was in fact twice as tall. I didn't believe him, so he showed me the part number in the computer - sure enough, he was right (not to mention a little ticked that I questioned his credibility). He said even with other manufacturers like GM, the filters have been getting smaller and smaller. Is this true? The filter I got was about the size of one for a GEO Metro (I used to own one, so I know). Is this a good thing?

Because of the height difference, the filter is really recessed way down in there and I could not get my filter wrench around it to tighten. In auto shop class, our anal-retentive teacher taught us to just hand tighten and then go 1/4 turn past that with a wrench. But now a wrench won't get in there, so I just hand tightened as much as I humanly could. It's pretty tight, but for peace of mind I would have liked to get my wrench on it for another 1/4 turn. I noticed on the filter itself it said to only hand tighten - that makes me feel somewhat better. And again, I torqued it in there as tightly as my gorilla grip would allow. I don't think it's going anywhere.

Anyone else get a midget filter from the dealer?

Oil Pressure at 2.75
 

Oh my god, did you say that you use Fram oil filters. I used to use them, and will never use them again. I only use OEM filters from the dealer or from Bosch. I once changed my oil, and then noticed that I also was only getting about 2.75 on the gauge. I looked at the wiring, and then the sensor as well. Finally decided that it may be the filter. Try a good filter (it is a cheap test to do of course), and then eliminate that as a problem source...

You anal-retentive teacher is correct, and even though you didn't say thanks, I'll go ahead and say: " YOU'RE WELCOME". See posts #5, 6, 7, 8, and 9.


Peter

Sorry - in all my excited haste to get this posted, I forgot to give credit where credit was due. Thank you Autozen, you were absolutely right. You saved me from possibly replacing my pressure sending unit. Thanks to everyone for their insight!

Autozen - what do you think about the midget filter? Could it possibly filter as thoroughly as a bigger filter with twice the element?

A few engine makers have gone to a smaller filter. Honda does it all the time and Yanmar shrinks one every once in awhile. If it bothers you Fastlane sells the bigger Bosch filters.

Castrol GTX is good stuff I used it in my Camry it really does work. It took 10k miles but my valve seals stopped smoking.

Most of the rice burners including my favorite, Toyota, are going to filters not much bigger than a large lemon. Many many years ago it was advised to change the filter every other oil change. Somehow America got on the idea of changing it every oil change. With the new no lead fuels, better combustion, and improved oils, I don't think there is much need for a huge filter.

Peter

Is anybody actually able to explain (and give data) why the more expensive oil filters are better? More expensive does not mean better quality. I usually use Fram or Bosch. (m103). No noticable difference in performance, oil pressure, and after I do an oil change, the oil looks the same in each case.

i had been using "pep boys' special" fram filters on my m103 for about a year after my case of OE filters ran out. then one day out of the blue, the pressure dropped to 2.75. needless-to-say, i made a bee line to the dealer for another case of OE filters. i learned my lesson the hard way as well.

Danwatt,
If you like to shoot craps, I suggest you go to a casino where you can only loose $20.00 instead of an expensive engine.

Peter

This is old I know, but I had a tour through the MANN filter factory in Germany in 1987. Was picking up about 12 tons of filters for the UK. They had a shop to test flow and pressure drop as well as a radio active engine test lab'. I also got to see other well known factories during the three years I drove truck to Italy and central Europe. Most of the factories then, making product under licence, seemed to be committed to quality control.

Now, I only buy MANN or OE for all the cars I service and encourage my customers to buy a pack of 6 OE filters and a drain plug washer and carry them in the trunk.

Most filters I have cut open lately of the generic brands have not shown any sign of poor construction or collapse...still....I don't need filter problems, have enough to do keeping up with my regulars vehicles. BMW mostly has an element for a filter like the 240/300D's and you can see the construction.....however, there is no mandated regulation for filtration particle size...no SAE standards, all companies ( Champion Filters, part of Allied I believe, ..) do, is test for burst strength.

You want a nice surprise? Buy a canister style Mann filter for a diesel MB. Cut open the upper part and be ready to see bugs, twigs, and cotton shells. :rolleyes: At least for 603's their all junk the OE filters at least use dirty white cotton without rocks, insted of the gray lint looking stuff the cheap filters use.

Unfortunitly the oil filter thread on the diesel forum was deleted. It did have a lot of good usefull info.

I've got, right here in my fat hand, a "Mahle" oil filter for the 603.

This filter is not the same as the one's made in India.

First off, it's made in Austria.

Second, it has "Mahle" and "Knecht" stamped into the top cover.

The outer construction is similar, but it's definitely not the Purolator from India.

We'll see.........................need another 5K miles to find out.

Knecht makes nice fuel filters maybe their oil filters are better.

Come on cut that sucker open I would like to know if their is a better filter before my oil change this week! :D

Nah. I'm not that excited about it to waste $8.50. :D

Figure that I've got to use them anyway. :o

Whats this stuff about bugs in the oil filters?
Are they manufactured that way, and which ones have the bugs?

The canister style filters that the diesels use have them. The bypass section is full of good stuff! :D I cut open an OE and a Fram they were both full of junk. The OE had white cotten at least. :rolleyes:

Boatguy,
Where did you purchase the OE filter that you cut open? It has been pointed out that A Bosch from India is not the same as one mfg in Europe.

Peter

I didn't intend for this thread to inspire debate - it's interesting to see the direction it's taking. All I can say is that the $5.00 Fram filter definitely caused a restriction or some other condition that resulted in my getting only 2.5 psi (eventually) at the oil pressure gauge. I replaced with a $13.50 OEM filter from the dealer and now the oil pressure is pegged. All I can pass on is my observation, and the fact that I've decided to never use a cheap filter again. I have no idea what the difference is technically speaking. For all I know, there could be grass and hay inside my OEM filter (I'm curious to cut one open now). But in my limited experience the old adage "you get what you pay for" always seems to hold true to some degree. Every time I have cheaped out it has always seemed to come back and bite me. Of course, that's to be taken with a grain of salt; paying the most doesn't neccessarily get you the best.