Radiator time for my 87 300D - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 03-25-2011, 11:18 PM

My radiator has been leaking from the side tanks for about a year and has gotten progressively worse. It's not exactly pouring out, but the drip marks on the garage floor (well, the cardboard I set down on the floor) are getting slightly bigger. The coolant went down a significant amount over the past couple thousand miles, too (none in oil though, had that checked). It isn't an emergency situation, but I'd rather not wait until it becomes one, so I ordered a new Behr which hopefully will be in tomorrow. My indy gave me some BG Products stop-leak to try, but I got so worried about clogging something that isn't supposed to be clogged, I decided to bite the bullet and replace the radiator.
Anyhow, I plan to do this tomorrow or Sunday if the radiator comes in. I have the FSM and the writeup in the DIY articles section, which is of a CE, not a diesel. Couple of questions, sorry if they're a bit silly, I'm terrified of messing up and overheating this car:
-Should I replace all the coolant at the same time as doing this job, or just drain and replace the radiator? It hasn't been replaced for about 4-5 years, though I see no signs of corrosion or muckiness in it (it's Xerex) and the car runs just about ideal temps. I'm leaning toward doing that a little later when I can make that nice big mess outside.
-If I just drain and replace the radiator, do I need to worry about "burping" anything? Or just add MB coolant into the reservoir and fire up the engine?
-To test the new radiator (and hose connections) for leaks, do I just pressurize the system at the reservoir? Can I buy/rent the tool to do so at a typical auto parts store?
-I'm also replacing the transmission cooler lines ... is that pretty much a bolt off, bolt on procedure? Do I need to do anything after replacing them other than add a bit of trans fluid to the fill hole and run the car?
Other than that I think I've got a pretty good handle on it, but if there's anything I should look out for or address that you guys can think of that might not be included in the FSM or this DIY (http://www.peachparts.com/Wikka/W124Radiator) please chime in.

Jeremy5848 · #2 03-25-2011, 11:23 PM

I recommend replacing the coolant.

BodhiBenz1987 · #3 03-25-2011, 11:32 PM

Quote:

Originally Posted by Jeremy5848

I recommend replacing the coolant.

Is the bleeding process pretty much the same as the 123? I had a really hard time getting all the air out of my 240D, even with it up on ramps. I must have done about 20 searches on that one, but I'll re-do for the 124. Would you want the reservoir tank to be the highest point, since that's where the air needs to escape?

babyjames · #4 03-26-2011, 02:24 AM

Just did this two-too-many times on the wag'n. Very straightforward. I had no trouble getting the air out of the system. Borrowed a friend's Snap On pressure tester. Don't really need it, though. I stick a funnel in the radiator end of the upper hose and pour the coolant in there until it is full, then connect it and fill the reservoir. All this with the front of the car elevated.

Start it with the cap off, selector set to defrost. Let it idle for a few, then gradually rev the engine to about 3000 rpm., hold it there for a few seconds, and slowly bring it back to idle. Check the coolant level, fill, repeat. Make sure you have hot air coming out the vents. Put the cap on, wait for the car to come up to temp, check for leaks. CAREFULLY remove the cap if you need to add coolant. Road test, re-check for leaks and check the coolant level. DONE!!

Jay

P.S. If the temp gauge starts to get too far above 80 - and it shouldn't - turn it off immediately! That would mean you have an air bubble in the thermostat housing.

aaa · #5 03-26-2011, 04:26 AM

I can't seem to figure out burping for some reason. No heat and temperature passing 100. So I just leave it for day or so and then suddenly it works fine.

BrianCostello · #6 03-26-2011, 09:50 AM

I would suggest a new thermostat too.

I have found that as the older stats "break in" they end up allowing 85 deg. Which is fine. but new thermostats will hold your temp gauge at exactly 80 deg.

So while all the coolant is drained. . .. if your gauge shows 85 and not 80 I would think about a new one.

other than that the rad change is very straight forward, and I have never had any issue with bleeding the system.

as suggested once your ready to start the car, make sure the coolant cap is OFF. Just letting the car idle, you will add another 1/2 gallon. with the heat on blast of course.

Brian

vstech · #7 03-26-2011, 11:02 AM

do you still have the original shroud on your car? it's a bit of a pain, but NOW is the time to swap it for the two piece one if it's not already been done.
I'd clean reallly really well around the cooler lines, before you open them up. the easy way to do it on ours cars, is under the car, disconnect the flex lines from the hard lines, and take the radiator out with the hard lines still attached. then swap it over to the new rad when it gets there.
4-5 years is a long time on coolant... I like to change it in 2-3. certainly pull the thermostat and test it in a pot on the stove with a thermometer. make sure it opens all the way, and make sure it starts opening at 80C (170 or so)
how's the fan clutch on your car? with the rad out, it's a snap to change.
also a good time to change the belt tensioner parts. (I had the spring snap on mine...) then of course, the best time to clean the a/c condenser is with the radiator out of the way.

babymog · #8 03-28-2011, 12:25 PM

Definately new coolant in 2-3.

I fill through the upper raidator hose pouring into the engine, and into the radiator. Never have had a problem with air in the system. Also as others have suggested, run the heat on high so that the heater core is filled, and so that the aux. pump helps to pull air and coolant through the head.

BodhiBenz1987 · #9 04-02-2011, 02:04 PM

Alright, new dumb question (I didn't get to this last weekend, too darn cold out, so doing it now) ... where on earth is the drain plug on my radiator? The new radiator has a nice drain plug near the lower radiator hose. My 240D's radiator had an obvious plug on the bottom of the radiator. The radiator that's in my 300D, I cannot for the life of me find the plug. I guess I can drain it by removing the lower hose, but that sounds messy.
Also, to clarify, do I want to do this all up on ramps? I know you do that in the 240, because you want the fill point to be the highest point so air will go there ... but is it the same thing when the expansion tank is the fill point, or are you better off on the ground?
And to clarify on the transmission cooler hoses ... does the system "prime" itself or do I need to try to fill the new lines with trans fluid? Obviously the new ones will be full or air when I put them on ... does that just get pushed out when the car starts up? So I can just add a bit of fluid to the normal fill hole?

aaa · #10 04-02-2011, 02:51 PM

Quote:

Originally Posted by BodhiBenz1987

where on earth is the drain plug on my radiator? The new radiator has a nice drain plug near the lower radiator hose.

That should be where it is. It's not a plug though, it's a valve. You stick a hose on a barb so it doesn't splash every where and then open the valve.

Quote:

And to clarify on the transmission cooler hoses ... does the system "prime" itself or do I need to try to fill the new lines with trans fluid? Obviously the new ones will be full or air when I put them on ... does that just get pushed out when the car starts up? So I can just add a bit of fluid to the normal fill hole?

Yes, just put them back on and refill, no need for anything special.

BodhiBenz1987 · #11 04-02-2011, 02:55 PM

Quote:

Originally Posted by aaa

That should be where it is. It's not a plug though, it's a valve. You stick a hose on a barb so it doesn't splash every where and then open the valve.

Oh I figured how that one works, but there isn't one on the old radiator that's currently in the car, which is the one I need to drain.

I can't find any plug or valve.

Thanks, re: the cooler hoses. Sounds easy enough.

babymog · #12 04-02-2011, 02:55 PM

The transmission cooler will purge itself.

If you have an all-copper Nissens radiator, there is no drain plug. Just one of the reasons I prefer the original Behr.

On ramps makes it easier to get beneath, but otherwise no reason. Just fill through the upper hose to the head and to the radiator, when it's full put the hose on. Run the car with the heater on so that the aux. pump helps to purge the head and heater core, should be all good.

BodhiBenz1987 · #13 04-02-2011, 02:57 PM

Quote:

Originally Posted by babymog

The transmission cooler will purge itself.

If you have an all-copper Nissens radiator, there is no drain plug. Just one of the reasons I prefer the original Behr.

On ramps makes it easier to get beneath, but otherwise no reason. Just fill through the upper hose to the head and to the radiator, when it's full put the hose on. Run the car with the heater on so that the aux. pump helps to purge the head and heater core, should be all good.

Thanks! I actually can't find a brand stamped on the radiator, but maybe that's what I have. Do I just drain it by removing the lower hose, then?