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  #1  
Old 02-01-2010, 08:32 PM
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1989 190D 2.5 - low pressure, high temp - any advice?

Greetings, eh?

Up until mid-January, my 190D 2.5 always ran at 80C when warm and 1.8-1.9 bar idle when warm. I use Mobil 1 5W-30 and the Mercedes OEM filter for every oil change. I recently changed my oil after a 5-hour road trip for Xmas 2009 (I've done it several times before, so I know to replace the filter gaskets/o-rings and the crush washer). I was getting the same readings until now - always rock-solid at 80C, WOT or warmed-up idle.

I let my car warm up to 80C, then started driving at 50 km/h. Once I accelerated to 70, the temp started increasing past 80C but not to the tick between 80C and 120C (90C? 100C?).

I pulled over and saw my oil pressure drop to 1.5 bar.

While the engine was running, I checked all of my fluids:
- oil seemed correct (except you can't tell with oil when the engine is running). I calmly panicked and added about 100-150 mL of oil. Stupid, I know.
- I added more transmission fluid since it was a little low.
- Coolant appeared fine, but I wasn't looking closely (it was a little low, and I fixed that yesterday).

I turned off the engine, waited five minutes, then rechecked the oil. It was now coating the red Max mark, but I don't believe that's a big issue. Wish I hadn't added oil anyway...

I turned the car back on and it sat at 80C and 1.8 bar again. Perfect.

I drove it from Olds to Calgary @ 120 km/h (1 hour) and visited my friends. When I drove it back to Olds, the readings were "bad" again. I assumed it was probably a bad sensor or thermostat and I could replace it later.

I drove it from Olds to Calgary yesterday and discovered that the readings were consistently 'bad':
- temp rises to 80C on idle, but when throttle applied, it slowly climbs, but never reaches the next temp tick.
- pressure stays at 3 bar on throttle, but on idle, it will hang around 1.5 bar, and has dropped to 1.2. The car sounds just as it always has, though - no rough running or knocking.

I noticed that the expansion tank was not at the proper fill level, so I added more coolant. This did not affect temp.

For all of these settings, they 'waver' - the needle slowly bounces like it's riding a lazy wave.

Here's what I'm going to check and/or replace.
- oil pressure sender
- coolant thermostat

I have access to a recent FSM for my car.

Any other ideas? Am I picking the right things to check?

EDIT: Also forgot - prior to these problems, I added a capful (not more than 15 mL) of a diesel additive to keep it from gelling and to keep my injectors clean. I did this each time I refilled my fuel tank (so that's twice before the problems started). I don't think I'm adding any more of this stuff for the time being, though.

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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.

Last edited by tuxbeej; 02-02-2010 at 07:07 PM. Reason: Forgot info about diesel additive.
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  #2  
Old 02-01-2010, 08:49 PM
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You should be running diesel oil, Mobil 1 Turbo Diesel & Truck 5W-40 would IMO be a better choice.

As far as your oil pressure, it is possible that your car has lost a head gasket between the timing chain cavity and the #1 cylinder. Watch for oil in the coolant recovery tank, or a peanut-butter like goo on the oil dipstick.

Also possible that you have cracked the cylinder head, the original head had a weak area that was corrected in later engines, lets watch fluids first though.

Other possibilities other than a bad thermostat; your thermostat has failed or your water pump is failing.
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  #3  
Old 02-01-2010, 08:56 PM
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1.2 bar or so idle, while warm doesn't sound too bad (the 5W-30 oil sounds a hair thin for somebody like me, much further south). The critical thing is full pressure (pegged @ 3bar) under any acceleration and instant response to acceleration.

My car routinely runs at 85C once warm. Maybe a bit higher with warm temperatures and A/C on. I would be concerned if I approached 100C (the assumed line between 80C and 120C). I think the turbocharged vehicles can fluctuate a bit more under full throttle. My temps will creep up under sufficient boost, and then cool down under light to moderate throttle.

If the sensors are correct, I wouldn't worry too much. I'm not sure about the fluctuation behavior. A non contact temperature probe might give you a good idea of how accurate the coolant reading is.

EDIT: The increased pressure after adding oil could be affected by adding cold oil and the overall viscosity of what's in your engine slightly increasing.
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Last edited by Crazy_Nate; 02-01-2010 at 09:18 PM.
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Old 02-02-2010, 07:27 PM
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Thanks, guys.

I'll keep a careful eye on the fluids to be sure I don't get goo or foam or anything like that.

I had read that Mobil 1 5W-30 met MB's specs for engine oil and it has a CF rating, which is why I was using it. I'll go double-check the bottle to be sure, though.

I also just found it weird that the first time I saw this behaviour, shutting the car off for five minutes, then restarting it 'locked' the engine temp at 80C for the entire drive to Calgary. I think it may have happened one more time after that, which made me wonder if it was a bad engine temp sensor or something else electronic.

But of course, that doesn't explain the low oil pressure on idle. To have it happen together, something may have happened to affect them both. I was thinking low oil, since oil also acts as a coolant.

I hope hope hope it's not a gasket.
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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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  #5  
Old 02-07-2010, 02:39 AM
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Drove to Calgary and back again yesterday. Same temp and pressure readouts.

When I got home at 0100h, I popped the hood, got out the flashlight, and wanted to take a quick peek to see if I was blowing any fluids or anything that might give me a hint.

I passed my ungloved hand over the top of the valve cover and felt puffs of air on my hand, in time with the engine idling.

I noticed that I was feeling these puffs from injector #1 (counting from the radiator to the firewall).

So I took a few pics. See attached.

That injector is definitely wet. I feel no puffs from any of the other injectors, and none of them are wet either.

So what to do? Here's the order of what I'm thinking:
- Disconnect the fuel line, remove the injector, clean up the area, reinstall the injector, reconnect fuel line, and test?
- Is there an O-ring to replace, or some sort of crush washer?
- Is this a case where I'm replacing an entire injector?
- Is this a case where I have to replace the valve cover gasket?
- Oh God, is my head cracked?

Am I leaving anything out early on? I'll look through my FSM, but if someone has advice, I would definitely love some. Thanks.
Attached Thumbnails
1989 190D 2.5 - low pressure, high temp - any advice?-leaky-injector-1-2.jpg  
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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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  #6  
Old 02-07-2010, 06:07 AM
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I did have similar problem - black goo coming from around #2 injector.
I did remove injector and glow plug and then removed precombustion chamber. After examining head, precup and I come to conclusion that retaining ring was not tight enougth. Retaining ring itself is multi spline type and requires special socket. It does require to have some experience to make proper assesment of condition of all parts involved. For example: bore for precup have to be measured to determine precup protrusion into combustion chamber. Sometimes, or if machining was required to the precup bore, shims are used to maintain precup protrusion into combustion chamber. In most cases just clean up an proper torque for seating precup in its bore is required to seal combustion gas leak passing by.
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Old 02-07-2010, 09:26 AM
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Quote:
Originally Posted by tuxbeej View Post

So what to do? Here's the order of what I'm thinking:
- Disconnect the fuel line, remove the injector, clean up the area, reinstall the injector, reconnect fuel line, and test?
- Is there an O-ring to replace, or some sort of crush washer?
- Is this a case where I'm replacing an entire injector?
- Is this a case where I have to replace the valve cover gasket?
- Oh God, is my head cracked?

Am I leaving anything out early on? I'll look through my FSM, but if someone has advice, I would definitely love some. Thanks.
I think I'd pull two injectors and swap them, to see if the problem follows the injector or if it's a problem with the pre-chamber. There are heat shield crush washers under the injectors which should be replaced any time an injector is R&R'd. You'll need a 27mm deep socket to remove the injector. Reinstallation torque is 70-80 Nm. You don't need to remove the valve cover to do this. Also, have some new fuel return line on hand before starting, unless your return lines have been replaced recently.
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Last edited by 300GD; 02-07-2010 at 09:36 AM.
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  #8  
Old 02-07-2010, 10:23 AM
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People have many thoughts about oil viscosity. Up in eastern Canada we feel in an older design diesel that forty weight viscosity is desired in the oils description. For example a 5w-40. The w signifies a winter flow rating I believe. Or a 10w-40. A 15-40 is good for summer use.

If engine is consuming too much oil it usually will reduce to about 1/2 of the heavier consumption with a straight 40 grade. This applies to summer use only of course.

It is important to keep a good layer of oil between moving parts. Your indicated slightly lower oil pressure could be from the thinner viscosity.

We are told from different sources that a viscosity of 30 is okay. Again the local feeling is it is inadaquate on older type diesels. On average our climate is cooler than what the majority of you have becomes a consideration as well.

The engine no longer sees the winter temperatures after the engine is totally warmed up. All it recognizes and indicates is that a thinner oil than usual is present.

For example if there was a 15-50 or straight 40 single viscosity oil in the engine at hot idle oil pressure might remain at the top.

I do not consider a discussion of viscosity effects an oil thread.
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Old 02-07-2010, 03:08 PM
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Quote:
Originally Posted by barry123400 View Post
It is important to keep a good layer of oil between moving parts. Your indicated slightly lower oil pressure could be from the thinner viscosity.
Agreed, as far as my "normal" pressure goes (1.8 bar). The sudden drop to 1.5 bar was very surprising and I think it's probably due to the leaky injector (but we'll see). It's still at 3 bar when I drive, though, so no issues there.

I referenced this link when I was choosing my oil. Pretty damn comprehensive. I think I may try 0W-40 next time I change oil, if I can find it cheap enough.
http://ferrarichat.com/forum/showthread.php?t=136052

Anyway, back to the problem at hand. I'll start with removal, cleanup, and reinstall/retorque of the injector (and get some new crush washers too). If that yields nothing, I'll swap two injectors to see if the leak follows the injector. I just replaced 4/5 of my fuel lines a year ago, so they should be new enough to not start leaking on me.

Thanks for all of the advice, guys. I'll keep you posted.

EDIT: Fuel *return* line, not injection lines. Ahhh... good thing I didn't start yet. I've never replaced my return lines. I'll have to get some.
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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.

Last edited by tuxbeej; 02-07-2010 at 05:07 PM.
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Old 02-07-2010, 03:18 PM
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When I've been on an interstate doing 70-75 for two hours on a 95 degree sunny summer day, I've pulled up to the stop light at the end of the exit ramp and seen 0.3, 0.4 bar oil pressure plenty of times. By the time the light has changed again, the oil has cooled and thickened sufficiently to be at least to 0.9 or 1.0 usually. As long as it still comes up under acceleration, I consider that completely and thoroughly un-alarming.

So I wouldn't be worried about 1.5 under ANY circumstances unless I was seeing 1.5 at 2000 or greater rpm.
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  #11  
Old 02-08-2010, 09:34 PM
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Bought a 27mm deep socket, 1/2" drive from NAPA. Despite it being deep, it doesn't appear deep enough. The internal ridges of the socket don't go all the way up to the end of the socket, so it catches on the fuel return barbs.

I'm going to have to get another socket, I suppose. Any manufacturers of sockets known to work (and hopefully I can get in Canada)?
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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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  #12  
Old 02-09-2010, 02:40 AM
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You are not going to like this thought. The increase in temperature might be from internal engine friction with too thin an oil. I doubt the rise in temperature is the air leak around the injector.

I hope my thought about the too thin oil is wrong. It might also be that the synthetic oil is not removing heat from the engine as well and the cooling system is working harder.
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Old 02-09-2010, 02:46 AM
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Bought a 1-1/16" socket from CDN Tire and it managed to fit (the ridges were deep enough.

Got the socket off and found a *ton* of dried carbon flakes underneath it.

My buddy cleaned the outside of the injector (he's worked on BMW 2002s before and was familiar with mechanical fuel injectors) and I cleaned the inside of the chamber extremely carefully.

After they were cleaned, we popped the injector back in, tightened it to spec, and took it for a drive. A lot of smoke at the beginning but once it got to temp, it drove fine and idled better than before.

The puffing from the injector was gone, but now I have weeping from the fuel injection line (which is over a year old, I think). I barely tightened it past finger tight, so we tried loosening it, reseating the line, then retightening it. We have less weeping, but the puffing is back.

It now feels like the puffing is coming from the part where the injector sits in the head. I'm thinking the next step is to take it to my friend's diesel mechanic and get a compression and leak test to see what's happening for certain.
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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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Old 02-09-2010, 02:49 AM
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You are not going to like this thought. The increase in temperature might be from internal engine friction with too thin an oil. I doubt the rise in temperature is the air leak around the injector.

I hope my thought about the too thin oil is wrong. It might also be that the synthetic oil is not removing heat from the engine as well and the cooling system is working harder.

A small percentage of us really old guys are reluctant to change the type of oil used after wear patterns have been well established as well. Just call us stuck in the mud if you wish. To do so and reduce viscosity at the same time below values that have worked for years does not seem like a sound move to me.

Even this far north again we always want to see a 40 weight or higher number in the multi grade formula. Never smaller. Call it old wifes tales again if you wish.

As costly as it is I might consider dumping the new oil into a storage container and get something else more appropiate in that engine. Too expensive of a potential gamble otherwise. Or it would be to me.
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Old 02-09-2010, 03:04 AM
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i have read everyone's concerns in here in regards to what oil I am using in my car. I will take those concerns under advisement as I move forward with my repairs.

I also apologize for touching off what seems to be a sore point in any automotive forum - the "oil thread".

I'll try to keep this thread updated with more info on what further repairs I end up doing.

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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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