Is the service manual procedure correct for replacing antifreeze on a 300SDL? - PeachParts Mercedes-Benz Forum

airfoill · #1 04-09-2003, 09:24 AM

Here is the scenario,

Last night I got through replacing the water pump on my 300SDL by flushing everything before hand and was ready to put the new antifreeze into the car. The service library procedure states that you fill the antifreeze through the overflow tank to the top, then run it until you get to 90-100C and keep the heater temperature at maximum. Well I was able to get about a gallon and a half in, at first then I ran the car to get the car up to temperature. The temperature finally got up to 100 but I was waiting for a sign that the coolant was circulating by touching the heater lines and also touching the radiator hoses.......they weren't even warm. I shut it off to see what was happening. I reviewed the service manual instructions to recheck myself and, yes, I followed them to the letter. I then turned it on again and the temperature went back up to around 100C and then one of the lifters started clacking loud, so I shut it down again. I then decided to open up the upper radiator hose to see if there was even any coolant in the hose, there wasn't any so I decided to add coolant to the engine through the upper radiator hose after the engine cooled down for a short period. It took about 2-3 quarts to fill at this location. I started it up again and then finally got some signs that the coolant was circulating and the temp gauge was at it's normal 80C. However, the lifter is still clacking loud. Did I overheat this engine using the service manual procedures? How does everybody else add coolant after a coolant change after everything is drained? Your comments would be appreciated. I hope I didn't ruin this engine. I'm beginning to think that the coolant never made it to the engine in the first place by adding it just through the overflow tank.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

Aaron · #2 04-09-2003, 09:55 AM

I always disconnect the upper radiator hose at the radiator itself and fill as much coolant through that hose as I possibly can. I then top up any needed amount through the expansion tank. This is especially effective on V8 engines as they are known for air pockets. If the temp only hit 100 celsius I wouldn't worry that you overheated it. Those lifters on the 603 motor are notorious for clacking loudly.

airfoill · #3 04-09-2003, 10:06 AM

I think I figured out your way, Aaron but the service manual should state this.

If i let the engine run on like I was doing the first time I filled the coolant, I'm sure I would have had a meltdown. Whoever wrote current procedure in the service manual probably never filled the system in practice.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

airfoill · #4 04-09-2003, 01:26 PM

Has anybody else filled coolant as stated in the service manual? I'm just wondering if I'm the only one here that had this problem?

The valve tapping sound that I have now did so when the engine was cold and went away once warmed up. Now, since yesterday, I the valve is tapping when the engine is even warm. What could have caused this?

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

gsxr · #5 04-09-2003, 03:20 PM

Herb,

The OM603 engine are notoriously irritating to fill with coolant. What I do is drain the system totally, including the block drain. That way I know how much I need to add (10 quarts for my 1987 300D - same engine as yours). Jack up the right front corner of the car high in the air. Add as much as you can to the top of the bottle. Wait until the level stops slowly dropping - this takes 5-15 minutes, it is NOT a fast procedure! Squeeze the upper radiator hose a few times. You can tell when there is liquid present in it. Don't start the engine until you have liquid in the upper hose!!! This should get about 90% of the specified coolant in. THEN start the engine, when it warms up, the level will drop slightly and you can add the final quart or so. I think the problem is most people do not wait long enough. They pour it in until the bottle is full, then go start the engine.

Your "valve tap" is likely to be one of the hydraulic lifters. This is probably a freak coincidence and had nothing to do with the coolant flush or engine temps. The noise is VERY common on OM60x engines. The cure, 99% of the time, is synthetic oil. I finally convinced my sister to switch from Delo-400 to Mobil-1 (15W-50). My BIL called today and said the lifter noises went away in days, and he wished he had listened to me & switched to synthetic 2 years ago (when they bought the car). If you use synthetic oil already, or the noise doesn't go away within about 5kmi after switching, it could be a collapsed lifter (or several). This is entirely possible with 150-250kmi on the engine. My car had 5 bad at 225kmi and I replaced all 12 of them, now it is nearly silent at idle!

(I kept the 7 good used ones as spares for my other car.)

Regards,

#6 04-09-2003, 05:03 PM

I filled the coolant bottle, started the engine and waited for the thermostat to open.. the temp guage will get hot but it is not a true reading.. it may take quite a while on a cold engine.. took mine about 10 minutes to warm up enough to open the t-stat and add the rest of the coolant.

gsxr · #7 04-09-2003, 05:18 PM

You can get almost all the coolant in the engine BEFORE starting the engine, as verified by liquid in the upper radiator hose. The t-stat does not need to open - it has a bleeder built-in. Starting the engine before it's full is the lazy/impatient method.

PaulH · #8 04-09-2003, 10:44 PM

Just filling the overflow tank and not having any water in the engine block sounds like a bad idea to me. One thing for sure; the temp. gauge sender will not read correctly until the sender is in liquid. Thus, how do you know what the real temperature of the engine is until the coolant is flowing? And, the thought of cold water going into a hot engine block doesn't seem right to me. If you are in a hurry, add coolant in the top radiator hose at least. And I would think that is why the T-stat has that little bleeder on it; so you can do it the "book" method way. Anyway, just some thoughts that may not have been considered.

#9 04-10-2003, 01:25 AM

I definately have to wait for the t-stat to open.. when it does it is a nearly instant rush of fluid out of the tank and into the block. The bleeder valve may trickle coolant in, but when the t-stat opens, you know it.

I keep a close eye on the engine while doing this, I know how hot it should be and how hot is too hot. You can't trust the dash temp guage.

Works for me just fine, and I don't have to bleed the block or jack the car up..

Ken300D · #10 04-10-2003, 07:25 AM

Thanks for the comments. I have this job coming up shortly. Also have a new serpentine belt to install. Hope mine is easier than TD's has been.

And while I'm griping, I wish we could get that blower fan replacement post back - I have that job coming up too. Already got the replacement motor. Squeak - Squeak - Squeak - Squeak!

Ken300D

mplafleur · #11 04-10-2003, 11:54 AM

Isn't there a plug on the engine somewhere that is used to finish filling the system? Otherwise an air bubble can occur.

gsxr · #12 04-10-2003, 12:29 PM

Nope. There's a drain plug on the block to totally empty the system, but no air bleed plug for filling. As I said, it's not necessary if you're patient...

airfoill · #13 04-10-2003, 10:43 PM

I feel fortunate that the engine wasn't toasted. The lifter problem went away after I drove it for a while.

Man do I feel alot better about this. From now on I am going to fill not only the reservoir tank but also fill the engine with coolant at the top radiator hose. I just didn't like the temperatures going up to the 100C and nothing was happening with the heater not circulating coolant and no coolant running through the upper radiator hose. The propensity for these engines to warp cylinder heads is high and I just don't want to take any chances. The service manual should be rewritten regarding this procedure. Nowhere does it say to be patient about filling it. All it says is fill it at the reservoir and then start it.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

mplafleur · #14 04-11-2003, 08:56 AM

I'm sure there is a plug on my m602, and I know I have used the one on my m103 when I rebuilt the engine.