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#1
11-21-2015, 12:00 AM
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86 300SDL Overheating Randomly
I gave the car to my dad to bring to florida for a few months to use as a car down there while i foxed up their florida car they never use. After he made the 1300 mile trip down there with it he told me it was overheating. HE put some antifreeze in it after he said it was low, (he's 70 and not always right)
 . My friend lives in the area and checked it out a month ago and it was hitting the 120 mark a few minutes after they started it. I finally made my way down here this week and cranked it up. I let it run for ten minutes and it ran fine, i drove it for about 20 minutes on the highway and side streets and it was 86 degrees out, I had the heat and AC on and the temp gauge was moving up and down but not above the 80C mark.Any idea what this might be? I would love to bring it back to NYC to let me mechanic work on it but I'm scared of it heating up on the drive. I don't want to junk it as I've put too much money in it to get it running right the past two years. We have owned it for about 5 years and it has 202k on it! The water pump and coolant got changed about a 15 months ago as well but it wasn't by my mercedes mechanic since i didn't find him at that point yet. 
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#2
11-21-2015, 12:32 AM
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If it overheats at a standstill, but not at speed it's a fan problem. Overheating while standing and moving is a water pump or thermostat problem.
__________________
'84 190D 2.2 5MT (Red/Palomino) Current car. Love it! '85 190D 2.2 Auto *Cali* (Blue/Blue) *sold* http://badges.fuelly.com/images/sig-us/302601.png http://i959.photobucket.com/albums/a...0/sideview.png
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#3
11-21-2015, 07:19 AM
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(he's 70 and not always right)
Great something to look forward to I guess!
__________________
92 e300d2.5t 01 e320 05 cdi 85 chev c10
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#4
11-21-2015, 07:26 AM
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Thermostat first. Has to be eliminated. Also when heating check for a collapsed lower hose. Or if it is currently really soft. Basically rotted but not leaking.
I am not aware if a sticking fan thermostat is not another possibility.
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#5
11-21-2015, 11:28 AM
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Quote:
On a serious note. This is what I would do if you want to drive it back to NY, provided the head gasket is sound. Wire up the aux fan to be on at high speed all the way. This can be easily done. Look for the 3 prong thermostat on top of the engine coolant tube to the radiator. Remove the 2 prong plug and jump them together. The aux fan would come on. Been there and done that when car in trouble. Good luck.
__________________
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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#6
11-21-2015, 12:04 PM
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Kind of a hijack, but I did what you describe last summer and it killed my fan. At the time I thought it was because I left the fan on at highways speeds, which I assumed was my stupid mistake...thoughts?
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#7
11-21-2015, 07:44 PM
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Quote:
__________________
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
11-21-2015, 08:24 PM
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Jumping the Fan
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__________________
 1986 300SDL 440,xxx Last edited by 86-300sdl; 11-21-2015 at 08:43 PM.
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#10
11-21-2015, 01:43 PM
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What was ambient air temp when your friend got it to hit 120 ?
If the engine was cold during the few min test, I doubt that the 120 was real given diesels tend to run cold at idle. I'd look at the temp gauge / sender and wiring. I've had the bridge break on thermostats and the main valve stick open and the bypass disc open as well. This results in an engine that runs hot at idle and cold at speed. See my post 5 1995 e320 running hot
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#11
11-21-2015, 01:56 PM
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For the cost Id be looking at replacing the thermostat again or at least pull it and do a stove top check to see what temp its actually opening at.
__________________
1985 300D 198K sold 1982 300D 202K 1989 300E 125K 1992 940T "If you dont have time to do it safely, you dont have time to do it" "The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."
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#12
11-21-2015, 04:40 PM
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Lots of good advice here but a 603 with goofy temp readings could be a cracked head or tired head gasket raising cooling pressure. Loss of coolant is one indicator. Is there residual pressure in the cooling system overnight? Do temp gauge fluctuations disappear or lessen if you leave the pressure cap on the first notch; that is, no cap pressure on the cooling system?
Sixto 83 300SD
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#13
11-22-2015, 11:52 AM
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Thanks for the reply gents. I've heard it said that the 603 aux fan is inadequate but I thought it worked pretty well. Well enough that I was fine without the mechanical fan; but the weather here is moderate in terms of heat. Plus I rarely hit stop and go traffic. Anyway hope I can get it fixed, seems like there is just one electrical component to wear out. Looks like a big resistor but it's probably a capacitor or something else. I've seen similar fans at the yard, maybe interchangeable. Well that's enough of a sidetrack. Cheers!
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#14
11-22-2015, 04:14 PM
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Quote:
If the fans are jammed, you may be able to revive them. The trick to disassembly is that the nut that holds the blade to the motor is left hand thread. Open the fan, clean and lube the bearings, hope for the best. The electric fans operate at two speeds. High speed is triggered by the switch that's on the water outlet, at the engine side of the upper hose. Unless it's a later car, in which case it's triggered by the climate control head unit. Low speed is triggered by A/C system pressure, by one of the pressure switches located on your receiver dryer. There is a resistor on the firewall that causes the fans to run at low speed. If you find the resistor has failed, it's possible that a fan is binding, which causes a powerful voltage surge. The point is, if you have to replace the fan resistor, you want to clean up your fan bearings as well. The high speed fan circuit is driven directly from the battery. The only protection is the relay, which has a built-in fuse. The early relays are black, and the fuse is internal and not replaceable. They are awful. The fuse can blow and you would never know it. If you buy a new replacement, it will be orange, and will have a replaceable fuse in the top. The low speed circuit is protected by two regular fuses in the fusebox. One for the relay coil and one for the contacts. Can they have made it any more complicated? TRoubleshooting electric fans
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#15
11-22-2015, 02:24 PM
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Several possible issues.
I'd check the belt spring and tensioner first. Next would be the coolant. Make sure he didn't put green in there. Pressure test the system...
__________________
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 560SL convertible 1987 190D 2.5-5SPEED!!!  1987 300TD 2005 Dodge Sprinter 2500 158"WB 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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