Thermostat replacement - PeachParts Mercedes-Benz Forum

cjl1973 · #1 11-13-2006, 05:24 PM

Ok, I have a new thermostat, and the lower radiator hose block heater coming from DieselGiant. Now this seems like it should be a pretty straightforward thing to do, but I do have a couple of questions.
1 How much coolant does an 82 300SD take?
2 Is there anything that I am going to need to do aside from the obvious? Drain radiator, pull hose, replace, open t-stat housing, replace, close it all up make sure drain plug is in and secure, fill.
3 Since I am not filling the radiator directly is there anything I need to do, or do I just pour properly diluted coolant into the expansion tank to the proper level?

I guess that is all I have for now.

DieselAddict · #2 11-13-2006, 06:48 PM

I'm not sure what you mean by the "lower radiator hose block heater". Normally there's no need to drain the radiator just to replace the t-stat and catching any spills underneath the car is good enough. In any case when you're done with the t-stat replacement you will need to fill the block first through the upper radiator hose, then the radiator through the expansion tank and bleed the system.

bgkast · #3 11-13-2006, 10:14 PM

1) According to my Haynes manual the car should take 11 L of coolant. I would use Zerex G-05 as it is much less expensive than the Mercedes coolant

2) I would drain the radiator using the drain plug on the bottom. If you are just replacing the T-stat and the coolant looks good you can just collect it in a clean container and reuse it. If it looks scummy don't forget to drain the block using the drain plug above the starter and the heater core.

3) can't help there...I don't have an expansion tank and always fill through the radiator cap.

cjl1973 · #4 11-28-2006, 12:52 PM

I finally got a chance to try to replace the thermostat today. I was going to drain the radiator, but the plug won't budge.
So my new question is this...
If I just open the thermostat housing how much coolant is going to come out? It looks to me like its more or less at the top of the system. Is the upper hose going to drain? I'll have a pan under the car to catch the fluid, but just wondering what to expect.

rrgrassi · #5 11-28-2006, 01:10 PM

Quote:

Originally Posted by cjl1973

I finally got a chance to try to replace the thermostat today. I was going to drain the radiator, but the plug won't budge.
So my new question is this...
If I just open the thermostat housing how much coolant is going to come out? It looks to me like its more or less at the top of the system. Is the upper hose going to drain? I'll have a pan under the car to catch the fluid, but just wondering what to expect.

Yes, the upper hose does drain, loss is about 1/2 to 3/4 of a gallon. You still need to "burp" the system.

Even though the T-Stat housing is a bit above the head, it is lower than the expansion tank and top of the radiator. Raising the front of the car up help reduce some of the loss, but it with still drain out to it's lowest high point.

cjl1973 · #6 11-28-2006, 01:15 PM

I hate to sound like a newbie here (I am) but how do I "burp" the system? This is not the kind of thing I want to screw up.

rrgrassi · #7 11-28-2006, 02:09 PM

Quote:

Originally Posted by cjl1973

I hate to sound like a newbie here (I am) but how do I "burp" the system? This is not the kind of thing I want to screw up.

You raise up the front end, refill the coolant through the upper radiator hose draining into the block, then refill the coolant tank. Make sure all hoses are clamped good, then start the car.

Idle and look for leaks, then take it for a short drive, and be mindful of the temp guage.

Refill tank if needed, and check for leaks again now that the system is pressurized.

vstech · #8 11-28-2006, 02:49 PM

the reply about the expansion tank being the highest point got me thinking...
how about if the tank is disconnected from the fender and set lower than the head? that ought to keep the spill to a minimum.
however if you need to pull the Lower heater hose to use the DG block heater you're gonna need to refill anyway.
it might be a good time to do a flush and clean out. then refill with Zerex G05 and Distilled water...
Just a thought.
John

lee polowczuk · #9 11-28-2006, 02:57 PM

do the zerex and distilled water....then you have a new baseline record...and really can forget about it for 3 years.....

i would buy some flush.. drain the existing coolant out and put in flush and drive for a week with water/diluted coolant....

then flush with tap water...then do the zerex and distilled...

i don't know why people are afraid to spend 25 dollars to do their coolant every 3 years... i notice this time and again..

vstech · #10 11-28-2006, 03:18 PM

Quote:

Originally Posted by lee polowczuk

do the zerex and distilled water....then you have a new baseline record...and really can forget about it for 3 years.....

i would buy some flush.. drain the existing coolant out and put in flush and drive for a week with water/diluted coolant....

then flush with tap water...then do the zerex and distilled...

i don't know why people are afraid to spend 25 dollars to do their coolant every 3 years... i notice this time and again..

a week in these temperatures? ya better keep the motor plugged in at night!

cjl1973 · #11 11-28-2006, 03:20 PM

Fear isn't really the issue. I've decided to put off the DG block heater, but still I need to do the thermostat. The big issue is that I don't have normal days off, and it is supposed to actually start getting cold here. I would like to have heat.