Engine Temp. Above 110C - PeachParts Mercedes-Benz Forum

Mike's Benz · #1 07-01-2009, 01:30 AM

I decided to buy and restore a 1986 300 SDL with 263,000 miles 9 mos. ago. A few weeks ago my temp. gauge went above 110C after a short ride up the street and back home approx. 3 miles. I read all the posts I could find about this problem and decided to replace the radiator with a new Behr and replace the viscous fan clutch also Behr and replace the reservoir cap. I used Zerex G-5 fluid. I test drove her immediately after, and the temp gauge went to 110C and settled there until I kicked down on the pedal to start the turbo and she climbed past 110C. I put the climate control on heat setting max, and she cooled down to 100C. Can someone tell me what these symptons mean and what more should I do to fix the problem? Thanks in advance!

300SD81 · #2 07-01-2009, 01:35 AM

Did you check the thermostat?

pawoSD · #3 07-01-2009, 01:36 AM

Sounds like there might be an air lock in the system, a stuck thermostat.....or the water pump may not be moving enough coolant....be careful with that 1986 diesel!! They can readily crack the heads if overheated....and you were very close to the magic danger zone. If you can't figure it out I'd have a MB dealer check it out before you crack the head and are looking at a waaay more expensive repair. The 603 engines do not like high temps like that.

oldsinner111 · #4 07-01-2009, 05:54 AM

I always drill two .064" holes in thermostat for bleeding air out.

Shawn T. W. · #5 07-01-2009, 07:37 AM

Quote:

Originally Posted by oldsinner111

I always drill two .064" holes in thermostat for bleeding air out.

Can you explain further please?

Got a picture?

Mike's Benz · #6 07-01-2009, 09:05 AM

I'll get to the water pump and t stat next so that I can examine them. I'm new to this engine so it takes me awhile. I most certainly did have an airlock in the system.

CANDIDE · #7 07-01-2009, 09:42 AM

Quote:

Originally Posted by Mike's Benz

I'll get to the water pump and t stat next so that I can examine them. I'm new to this engine so it takes me awhile. I most certainly did have an airlock in the system.

Park the car facing up on a hill and remove top radiator hose. Do this when engine is COLD. Pour coolant mix into hose, this will fill the cylinder head with coolant. Also, it takes a few heat cycles to burp air from system, and it might take a couple of radiator hose fills. You might want to examine cylinder head to see if you have the #14, the numbers are driver's side near cylinder #2's intake port.

mplafleur · #8 07-01-2009, 10:45 AM

Since you just filled it, it certainly could be air in the system.

I hope this was your problem and temps are back to the same as my '86 SDL, 82*C .

latitude500 · #9 07-01-2009, 10:47 AM

Quote:

Originally Posted by Shawn T. W.

Can you explain further please?

Got a picture?

I ended up taking a drill bit and drilling two holes in my t-stat so that the coolant could flow past the t-stat all the time. It helps cool down the car. You’re going to need to remove the t-stat from the t-stat houses. Look around the alternator and you will find the radiator hoes that goes into the housing. You will need to remove the bolts that hold it in place and then take out the t-stat and drill two holes into it. Be careful not to damage it, or you will need to purchase another one.

I’m afraid I didn’t think about taking any pictures of the t-stat after I drilled the holes. But I do have an extra one with holes drilled in it in my garage. So let me know if you want to purchase it off me. It is for an 87 300SDL. You might want to purchase a radiator flush, and flush out the system. I have 200K+ on my 300sdl and I ended up doing the flush before I started replacing expensive parts. On these old cars, I would think it would be part of the over all cost of ownership.

P.S. I live in Austin Tx, the temp has been around 103 degrees for four days.
Good luck and be careful.

Mike's Benz · #10 07-01-2009, 11:36 AM

The numbers on the head read R603 016 14 01. There is some leakage of coolant around the #2 intake port gasket.

pawoSD · #11 07-01-2009, 11:53 AM

That is the infamous "#14" head......it will readily crack if the temperature gets too high....so I'd be extra careful in getting the cooling stuff taken care of without overheating it.

Mike's Benz · #12 07-01-2009, 12:17 PM

How do I know if it cracked already?

pawoSD · #13 07-01-2009, 12:34 PM

Quote:

Originally Posted by Mike's Benz

How do I know if it cracked already?

It will either be:

-burning coolant (white smoke in exhaust at all times, especially startup)
-oil in the coolant reservoir
-coolant in the oil (if the oil looks watery on the stick)
-upper radiator hose remains pressurized after the engine has cooled down

Mike's Benz · #14 07-01-2009, 12:39 PM

Thank you. I'll work on this.

CANDIDE · #15 07-01-2009, 12:58 PM

Quote:

Originally Posted by pawoSD

It will either be:

-burning coolant (white smoke in exhaust at all times, especially startup)
-oil in the coolant reservoir
-coolant in the oil (if the oil looks watery on the stick)
-upper radiator hose remains pressurized after the engine has cooled down

And, coolant loss.
My #14 head had 7 cracks and used about a pint of coolant every 500 miles. The upper radiator hose was pressureized even when cold. When I tried to do a compression test, coolant shot out of 2 cylinders and soaked the hood insulation...no need to test further.
When I bought "Whitey" (artic white) I was unaware of the #14 head issue, I've upgraded to a #20 and learned much along the way, thanks to this forum.