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#1
11-24-2014, 10:04 PM
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'86 300SDL. New to the MB diesel world. A few ?s
Ok, so my background in auto repair is primarily gas engines and what little bit of diesel repair I have done has been older Ford, Chevrolet, and Dodge trucks. A friend of mine has a 1986 300SDL, 3.0L turbo diesel that he asked me to look at.
The car has 253,000 miles and has been regularly and properly maintained its entire life and is treated very well. It has recently started losing coolant. I have been all over this thing and it is not leaking externally. I've put cardboard underneath it and searched throuhout the engine bay and no coolant traces. After doing some research I have learned that #14 cylinder heads are prone to cracking and read symptoms of when these particular engines blow a head gasket. I have a #14 head. I believe I may have a cracked head. I read that if you drive the car and get it up to temperature and then let it cool down, once it has cooled, the cooling system should not have pressure on it. (Please feel free to correct me if that is not entirely right) If it has pressure on it hours after being cooled down, then you most likely have a cracked head/blown gasket that is allowing exhaust gasses to enter the cooling system and the pressure stays in the cooling system. Any experts care to weigh in? Next, after driving this 300SDL, I hope to be in the market for a smaller diesel MB in the near future. Preferably manual transmission, turbo and lots of options are not a necessity for me, any suggestions? Thanks in advance, -Matt 
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#2
11-24-2014, 11:04 PM
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Welcome!
I enjoy my non turbo 5speed manual 190D. Sporty, and very miserly on fuel. The cold pressure remaining on the cooling system is a fair sign of gasket trouble... Not conclusive, but reasonable. The coolant could equally be spilling out the overflow at speed from a weak fan clutch, or a dirty radiator.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!!  1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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#3
11-25-2014, 12:17 AM
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Quote:
Gasket trouble is sort of what I was leaning towards. I don't think there will be any way to know for certain that the head is cracked without removing it and having it checked. There is some slight oil moisture at the front of the cylinder head as well and I get a slight rattle or peck on cold startup that usually goes away after a little bit of driving. (Not sure if that part is normal or not) I considered that, but you would think if that were the case the temperature gauge would run up a little higher and this one has not gone even the slightest above normal. I haven't done any hard runs or anything like that, just driving it around town at 25 to 50 mph. I do live in the mountains, so there are a few "hills" and the temperature didn't climb while going up them.
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#4
11-25-2014, 08:06 AM
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Any indication of coolant in the oil?
If the engine has been overheated, this would lead one to think of a cracked head. It seems you're on the right path by pulling the head to asses any damage.
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83 SD 84 CD
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#6
11-25-2014, 10:55 AM
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Some info on #14 head here
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.  W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html 1 X 2006 CDI 1 x 87 300SDL 1 x 87 300D 1 x 87 300TDT wagon 1 x 83 300D 1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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#8
11-26-2014, 12:12 AM
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Even not having pressure in the cooling system the next day isn't conclusive because any leak in the cooling system or a faulty cap will bleed telltale pressure.
Your car should have a coolant overflow bottle behind the right front wheel. Follow the hose from the reservoir into the fender. The wheel well liner will have to come off to inspect it. Point is, you can lose coolant and not have it drip to the ground immediately. Sixto MB-less
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#9
12-02-2014, 03:52 PM
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Quote:
Yeah, I did check there and it is not coming out there. The head will be coming off for a refresh and hopefully the head is ok and the gasket is just blown. Even if I have to buy another head, the cost of fixing it will be well worth another 250k miles.
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#10
12-03-2014, 05:33 PM
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My 87 300sdl had the same problem. Has your coolant overflow tank turned brownish black instead of clear and can you see small oil droplets floating in the water? Do you have oil leaking out of the side of the motor around the turbo?
My #14 head gasket was blown. Same symptoms. I was also overheating. I went to junkyard and found full motor with #22 head for $160 out the door. I took head off and sent it to machine shop and got valve job for $300. Had him replace the stem seals also. The rest of the gaskets and such cost me about $500+. Runs like a champ now. You can clean the reservoir off the car with gasoline and it gets most of the black out. Also look at the clips and shims that hold down the injection lines from the pump to the injectors. I didn't put these back on when reassembling and cost me 8 lines @ $50 each before I replaced all the fasteners. They will vibrate and leak if not properly secured. Control arm bushings. Do not buy these and have shop install. Buy the whole control arm assembly. Cost me a lot more in labor to change them out then the added cost of the whole control arm. Use diesel purge on the engine and replace fuel filters after. I think superturbodiesel has a how-to using a couple rubber hoses and an empty juice bottle. I do this at least once a year. Do not ever buy any parts manufactured by Uro. Do not ever buy Meyle suspension parts. Some Febi parts are junk too. Replace all vacuum lines. Delete egr and emissions equip under airbox. DIY online for this.
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1987 300 SDL 2000 E320 Wagon
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