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  #31  
Old 03-31-2002, 12:13 AM
ebiker
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1987 300TD confusing running hot problem

OK, first of all, if you have a cracked head--combustion chamber into cooling system--you will know!! As you drive the car, You will lose all of your coolant. I have been there, to the tune of $2,800. (Rebuilt head). If you have a slight combustion leak into cooling system, you will see bubbles in the coolant. Diesels have 22:1 compression ratio. The Mercedes Benz radiator cap is rated at 17PSI for the 87 300D. But, do check with a dealer on this. I had suggested MB antifreeze because of the aluminum parts. The auxillary fan cuts in at coolant pressure of 20-Bar. It's also affected by coolant temperatures of 110-C. Of course, relays and switches control this operation. Temperature sensor could have overheated and thus become faulty when the motor overheated. That sensor is B11/7, it's up by the fuel filter. Finally, I assume that the Mono valve and the auxillary circulating pump are good. I wish that I could offer you more help.

Ed.

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  #32  
Old 03-31-2002, 01:30 AM
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Um, Ed... it is possible to have a cracked head and not lose coolant. You will lose coolant only after the crack becomes extreme. Initially there may not be any coolant loss. I just replaced my head too, cracked in 3 cylinders, and I had no coolant loss - just high pressure when cold. Search for other threads in the last 3 months on this subject. "Bubbles" are not visible or present - just abnormal pressure.

Also, the radiator cap is rated at 1.4 bar, which is roughly 20psi - not 17. And the aux fan operates as I stated in my previous post - NOT as you describe. If you study the W124 Electrical manual for the 1987 300D you will understand. And as I stated before, the aux fan operation will not have anything to do with Henry's problem. The car will stay cool enough without the aux fan under normal (i.e., non-Death Valley) conditions.

Oh, one more thing: Sensor B11/7 is only used on the 5-cylinder diesels from 1990-up, it is a preglow temp sensor. The 1987 model has a different sensor in this spot - B11/4, which is for the EDS (Electronic Diesel System). The 1987 model has no external preglow temp sensor, it is built into the preglow relay (senses ambient temps only, not engine coolant temp.) This would not affect the cooling system, ditto for the monovalve, and aux coolant pump (which only helps keep hot water in the heater core at idle, when the water pump doesn't provide enough flow there.)



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Last edited by gsxr; 03-31-2002 at 02:04 AM.
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  #33  
Old 03-31-2002, 12:09 PM
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1987 300TD confusing running hot problem

Well, let's see now, Dave M. As I pointed out, my 87 300D cylinder head cracked in the COMBUSTION chamber resulting in an entire loss of coolant within a few miles. I was driving the car @ 75mph when this occured. Later, at the MB dealership, the technican poured water into the cooling system, I started up the motor and water shot up out of the expansion tank. That 22:1 compression has to go somewhere!
The MB maintenance manual cooling system test specify's a pressure test of 1.0-1.3 bar. Of course the rest of the MB maintenance manuals, (3) could contain more misinformation, too.

Your right, Dave.

After 12 years and 177K of owning my 1987 300D I'm wrong.

I'm outta here!

Ed.
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  #34  
Old 03-31-2002, 01:12 PM
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Ed, like I said - yours is the extreme case. It is possible to have minor cracks without coolant loss. See photo below of one of the 3 cracks in my head, with NO coolant loss. I think you missed the early warning symptom of high pressure when cold.

Now, about the pressure ratings. Section 20-017 of the OM603 engine manual states that the cooling system is to be checked by pressurizing to 1.4 bar. Also, section 20-430 states that the original 1.2 bar radiator cap has been superceded to a 1.4 bar cap, the 1.2 is no longer available. I'm not sure what the "maintenance" manual is. There are 2 chassis manuals, 1 electrical, 1 climate control, and 1 engine manual, and the Technical Data Manual. I have all of the above and also the Mercedes 124 CD-ROM, which has a "maintenance" manual section, which just outlines what items to check at particular intervals, IIRC- not actual service procedures. I'm not pulling this stuff out of thin air, really! It's all in black & white. And yes there are errors and contradictions in some of the manuals, particularly the electrical manual. However if you compare different sections you can determine which part is correct.

Update : I just checked out the 124 CD-ROM to see if I missed something. It appears that the Maintenace Manual has more in there than I recalled (oops). However, it is a generic manual for all Mercedes models, not just the 124 chassis. The section on testing the cooling system does spec 1.0-1.3 bar, but that is for chassis 107, 123, 126, and 201 (up to ~1985). None of those cars used the OM603 engine. The OM603 engine manual does spec 1.4 bar for test purposes. FYI, the newest MB's (210 chassis, I think) have some engines with 2.0 bar (~29 psi) caps! Wow... that's high pressure.


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1987 300TD confusing running hot problem-crack5.jpg  
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Last edited by gsxr; 03-31-2002 at 02:27 PM.
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  #35  
Old 03-31-2002, 01:13 PM
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And here's a pic of the crack in cylinder #6. The third crack was almost identical to this one in cylinder #1.
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  #36  
Old 03-31-2002, 04:54 PM
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Finally pulled the head - started another post. Based on what I have seen so far I suspect I had a tired head gasket, maybe just trying to justify pulling it off .
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  #37  
Old 04-01-2002, 01:26 AM
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The saga continues.

I checked to see if I had pressure in the coolant system this morning. Nada, zilch, just soft hose and no pressure when I removed the cap.

Having nothing better to do today I decided to take out the t-stat and check it with the spare MBZ t-stat. I had forgotten what a PITA it is to remove them. That top bolt is just out of reach of the socket and I could barely get my finger on it. That coupled with the goofy routing of the line to the expansion tank just seems to get in the way. I was so temptemted to remove the air supply duct but I also remembered how hard it is to get it back on around the sheet metal heat shield. Anyway, got it out, checked in hot water. Both opened at about 176Deg F and where fully open at boiling. at least I guess thay are. No real way to tell if they can or should open more. I wish the manual had some measurement info on the t-stat operation. So two good t-stat's. Went back to the MBZ one. Car still runs hot. On the power run at 85mph, with ambiant at 63deg F. the temp gauge went up to a needle width of 100deg C and on the hills sneaked ever closer. I am truly confused. I can only assume that the head has some minute crack that was missed on the pressure test and it is not contributing to coolant loss or system pressurization or I have some strange back pressure problem on the exhaust. The timing on the car seems to feel right. That is what I will checked next. I recall the manual has some test that was done to check if the trap was plugged. Glad that there is no trap on this car. Or what I would like to think is that the original t-stat in the car was different than the ones currently available. (I must remember, NEVER THROW ANYTHING AWAY)

I would guess that timing issues that would cause the car to run hot, would also affect cold starting and power. this car has none of that.

Did a search on the running hot problem and this seems to be an issue for a bunch of these cars. Also, there is a lot of dicussion about bleeding air out of these engines. I remove the top hose from the radiator and pour in the fluid until it starts to spiil out, then fill from the expansion tank. Then set the heater on high and let the car get warm. Seems to work. I do miss having a cap on the radiator.

henry
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87 300SDL 135k
87 300TD 280k (sold)
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  #38  
Old 04-01-2002, 02:22 AM
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Henry,

If your hose is soft your head is probably fine. I doubt it's cracked. I know it sounds crazy but I suspect your "new" (6-mo old?) radiator. Is there any way you can get a different (new) one to test? Marshall Booth (MBCA Tech Advisor) pointed out that if the last one plugged, the system should be cleaned BEFORE installing the new one, or residual crud may plug up the new one ASAP resulting in the same problem. Did you do a citric acid flush at any point? Your t-stats are OK too. (BTW, a tip to ease removal is to yank the temp sensor in front of the housing - makes it a LOT faster too!) I also doubt you have air pockets, as long as you are getting 2 gallons back in after draining. Timing, as you say, probably isn't it either. Wouldn't hurt to check though. Did you ever check the A/C condenser for crud? Is it nice and clean?
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  #39  
Old 04-01-2002, 09:17 AM
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Not to confuse matters (any more than they are already) but my car was running a few degrees warmer than it had been last night (and it was COLDER 40F) so I let the car sit overnight and check for coolant pressure in the AM - YES Wheeled straight into mechanic this morning asked about coolant hose should be able to touch sides together, "yes" was answer. Said I couldn't do it, eyes light up was his response. He seems to only have seen diesels with head that have REALLY cracked because he said you go down the street and you are done. Will find out more on Wednesday when it gets some new A/C parts. The odd thing is that it WAS running 90C steady at first and then seemed to over a few days get a little warmer.

If I had a small head crack (could is be as simple as a bad gasket?) what are the chances of it getting worse? Should I just leave it? The car never goes past 98C, its basically the same as HGV's right now.

Brian
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  #40  
Old 04-01-2002, 10:36 AM
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Brian,

Yes, it could be the head gasket. But given the history on this engine (OM603.96x) it's more likely to the the head. The only way to tell is to pull the head and check. Maybe you'll get lucky!

As to whether you should just leave it, it's up to you. I bought a car with this problem last August, and have driven it 8kmi since then. It had lots of oil in the coolant tank at the time. I flushed it out, tried K&W Block Seal (no luck), and have been driving it anyway. I don't have oil in the coolant anymore but I get high pressure after one full throttle run to 60mph! All winter the car ran at 82C on the gauge, almost never budged over that. Yesterday it got to 85F or so and I had the A/C on. The temp would fluctuate between 85-98C, which isn't *that* hot, but it should move around as much as I saw. Last fall when I bought it, I noticed that heavy load when warm would raise the temp FAST. My other (good) 300D does not have these fluctuations. I plan to yank the head in the next few weeks (been finishing up my other cars first).

So yes, you could drive it for quite a while like this - just be aware that it could be a ticking time bomb. Watch the temp gauge VERY closely, especially when the weather gets warmer and/or you start using the A/C. I know another guy with the same car (1987 300D), with similar symptoms, who is also driving it - with no head removal plans. When I do pull mine I'll be taking pictures and posting my findings here, so y'all will know what happened...

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  #41  
Old 04-01-2002, 12:40 PM
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Yes, I did check the condenser and it is clean. I also changed the radiator with a new one and it had no impact. I will drive it until it gets in the red then I will attack it again. I will put some wet water stuff in it and see if it makes a difference. Until then, I have given up on this one. Will continue to keep a close I on pressure in the hoses and check for oil in the coolant.
What temp should this car run at and when whould I worry?

Henry
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76 BMW 2002 (sold)
86 190E-16v (Demised at Laguna Seca Turn 9)
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87 300SDL 135k
87 300TD 280k (sold)
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  #42  
Old 04-01-2002, 04:48 PM
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Normally it should be 85-90C. In summer with A/C on more like 90-100C. Anthing over 100-105C isn't normal. The "Worry Zone" is 110C and higher.

At 120C you better turn the heat on full and/or shut off the engine ASAP...
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  #43  
Old 04-02-2002, 09:09 PM
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Well I went out and bought the water wetter and I have a 300 mile road trip up to the Geysers in California. There is one long 18.5% grade that I have recently ended up with the heater blasting and all the windows open. I will see if this does the trick and report back. Thanks for all the advice.

I was also looking at running synthetic oil, but at $40 every 5K miles it seems pricey. What is the upside? Can you spread out oil changes?

I have always specified synthetic oil for rotatiing equipement that must run 24/7 for 12 months at a time. This is what it was it meant for. It seems that if you can change oil on a regular basis, it does not warrant the cost.

Am I all oily behind the ears?

henry
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63 190d (sold)
69 220D (sold)
69 280SL (sold)
76 BMW 2002 (sold)
86 190E-16v (Demised at Laguna Seca Turn 9)
87 300SDL (sold)
87 300SDL 135k
87 300TD 280k (sold)
95 E320W 211k
95 E320w 111k
05 C320 4matic
06 E320 CDI 90k (Totaled by a texting 19 year old girl in a nissan)
2013 GLK 250 Bluetek 4MATIC
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  #44  
Old 04-02-2002, 09:47 PM
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Henry,

First, using synthetic oil won't solve your hot running problem. With that said, yes, you can run an extended drain interval when using synthetic oil. Assuming you don't operate the car under "severe service" conditions (i.e., mostly city driving, stop & go) you can push out the oil changes to 10kmi easily with most any synthetic (Mobil 1, etc.) Beyond that I wouldn't do it unless using diesel-specific synthetic - Mobil Delvac-1, Shell Rotella Synthetic, Amsoil Diesel, etc. These are specially designed to handle the extra soot that will develop over the longer interval. Delvac-1 is one of the best out there, the Amsoil is good also. The Shell stuff is new and unproven but should be OK too. Using these, maybe 15-20k would be possible, especially with lots of freeway driving.

The only way to verify the "safe" limit is with an oil analysis, which is available from numerous sources. I use the Mobil Delvac AccuTrack "extended drain" analysis, it's $13 for the kit (plus S&H both ways, figure ~$20 total per analysis.) I am using Delvac-1 oil, changing the oil every 10kmi, and changing the filter every 5kmi. My oil consumption is 1 quart per 7500 miles or so. The oil analyses (sp?) shows that at a 10k interval everything is peachy. I could probably go longer, but I only put ~10kmi per year on the car so I figure an annual $45 oil change isn't bad. I drive a mix of city & freeway miles. If I drove all freeway I would change it at 20kmi (assuming the analysis was OK.)

Other benefits include lower oil temps, marginally lower coolant temps, faster cranking, faster cold oil pressure building, faster cold starting, less wear on startup, higher "safety zone" under extreme operating conditions, and some other things I can't remember right now. I've heard (Edmund?) that using synthetic ATF helps lower coolant temps a hair as well, since the ATF cooler is inside the radiator. I plan to switch to Mobil-1 ATF at my next tranny service (21kmi and 11kmi away on both my '87's, repsectively.)


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  #45  
Old 04-25-2002, 11:24 PM
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I have been waiting to let everyone know what the results are of everything I have done to the car and how it is running. I have replaced every possible component of the cooling system and have come to the conclusion that as long as MY car does not overheat into the red, I will live with the results of my labor. I went up to Tahoe on monday at a sustained speed of 70 with an ambient temp of 75-80 deg f. The car ran between 95 to 110deg C. This is hot but not overheating. On the return trip going through Sacto with AC on and ambiant at 85-90 deg F, the car ran about 90-105 Deg C. For me this will have to be acceptable. I also got 26.5mpg on the return. Car burns about 1qt/1500miles and I can live with that. I do admit that the car runs hotter than before, but I will have to life with that akso. My car has 203000 miles and if I can make it to 300k, I will drop in a factory rebuild. I put about 30k a year, so maybe if I am lucky, I will put a new engine and go for my 500k badge.

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63 190d (sold)
69 220D (sold)
69 280SL (sold)
76 BMW 2002 (sold)
86 190E-16v (Demised at Laguna Seca Turn 9)
87 300SDL (sold)
87 300SDL 135k
87 300TD 280k (sold)
95 E320W 211k
95 E320w 111k
05 C320 4matic
06 E320 CDI 90k (Totaled by a texting 19 year old girl in a nissan)
2013 GLK 250 Bluetek 4MATIC
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