1987 300SDL Radiator/Water Pump/PS Pump/TStat/Hose/Coolant Replacement
 

Recently, the AC compressor on my 1987 300 SDL began to groan and ultimately locked up. Luckily, I towed it home and avoided major engine damage. However, In trying to remove it for replacement, I came across a laundry list of problems that I now have to deal with.

I'm an average at-home mechanic and feel quite capable of tackling any of the upcoming tasks. However, given that some of them I have not done on an MB, I'm looking to sidestep what may be common pitfalls that I do not know about.

Any advice that can be offered is greatly appreciated. Hopefully, all work will be completed this weekend and I can report back on Monday how it all came out.

Thanks in advance.

1. Remove and replace radiator. Upper inlet pipe broke off.
2. Remove and replace PS pump - brackets sticking off of housing appear to be crumbling.
3. Remove and replace AC compressor. I'll take it in for flush/recharge, unless it's not too difficult (never attempted before)
4. Remove and replace water pump. Seems to be working fine, but while I'm down that far, might as well.
5. Replace TStat (same reasoning as #4).
6. Replace upper and lower rad hoses (same reasoning as #4)
7. Test and replace any bad glow plugs. This appears to be fairly straightforward for this car. However, on my 92 300D 2.5, I cannot gain adequate access to 2 of the plugs without removing the over engine air intake equipment/throttle linkages.
8. (obviously) Flush and fill coolant system.


Thanks,
Pete

92 300D 2.5 384,000+
87 300SDL 244,000+

With the 603, the philosophy is that it is probably best to replace all the glow plugs at the same time because you need to pull the intake manifold to do it unless you have miniature hands.

I recently bought six plugs and an intake gasket for the SDL. We'll see if I can get that far down the laundry list before the winter gets here.

Wow thats some expensive work! :eek: Change the trans cooler lines while you have the rad out, their $10 each and probably shot.

Water pumps are one of those very rare items that are cheaper at the Mercedes dealer than anywhere else. Plus there are lots of horror stories surrounding the use of aftermarket water pumps. Problems caused by poor impeller design, in particular.

Yes buy an oe water pump, but the radiator's are all the same. Behr is the only company that makes a radiator for the 300SDL. I got mine for $395 and you should to, the dealer wanted around $570. Shop around and buy the cheapist one their all the same! I can see where they ground the star off on mine!

Cost not too bad...
 

Thanks for the tip on the trans lines, Hattaras. I'll probably do that if I can get them in time.

Thanks for the water pump tip, Tango. I wish I had known that earlier, I already have one on its way. I hope there doesn't end up being any trouble

Brian, believe it or not, I was able to manipulate the glow plugs on my 92 300D in and out using a socket extension and a deep socket. I set a small powerful magnet on the outside of the socket and it held onto the plug and nut as I maneuverd them in and out. However, on that car the washer bottle is in the way of #2 and 3, so I have to remove either the washer bottle or the intake manifold. The 300SDL seems to be a clear shot.

I consider myself fortunate that I heard the compressor starting to grind and stopped driving it before it froze - it finally locked and burned up the belt trying to start it for the last time to back it into the barn for repairs AFTER I had hauled it home. It could have gone on the highway and wrecked my engine before I knew what hit me.

Otherwise I'd be posting a series of "parts wanted?" notices on here.

So costwise, I'm way ahead of the game just based on that.

As for the other items:
I found a rebuilt compressor on ebay for $171 shipped.
Already had a Tstat, poly belt and glow plugs ready and waiting.
Lower rad hose is funky and cost $95, but the upper is only $11.
I found a used radiator on ebay for $63 to put in for now - will get mine rebuilt, put that back in, have the ebay one rebuilt and probably sell it online.
PS pump works fine, but needs some TLC on the front brackets. I'll have some pieces mocked up and maybe welded on by a buddy.
Water pump was $55 shipped (I hope I don't have any trouble with it.)
I'll pay my indie $40 to $60 to evacuate and fill the AC system.

All in all, not too bad. I peg it at about $3000 or so at my indie, so I'm happy because what is listed above is far less.

I hope this is near the end for a while, though. I've already dropped $2700 for a rebuilt transmission and another $1800 on misc. stuff since I bought this $3000 car in June.

Drives like a dream, though, and I can't wait to get it back.

You're a good man, Pete. Now how 'bout heading up here and doing mine? :D

Is the radiator for the SDL by Behr copper or Aluminum? Is there a Copper radiator for the 87 300D or is the one I got a fluke and i should replace it with a Nissens Aluminum one?

As for the AC compressor seizing up, I thought the compressor on these cars had a relay that lets the clutch go when the compressor fails so that it doesn't shred the Serpentine belt?

AC Compressor Sieze Up...
 

Jmak,

There may be some type of fail safe, but I'm pretty sure my main shaft snapped. The pulley wobbled for a good while, which was the noise that I heard. Then it finally stopped altogether. I'm sure that the bearings jammed up.

I can't tell for sure because I cannot get the pulley/clutch off of the compressor. Does anyone know how?

Compressor! it finally locked up and stopped??
You'll need to replace the reciever/dryer when opening the system. It also sounds like the compresor trashed itself and probably contaminated the system. A system flush would be in order. Or your going to open it again in a few weeks.

Dave

Compressor
 

I don't have any experience with AC work, so I'll just put the compressor on and connect everything so that I can drive the car and not use the AC. Before next summer when I need it, I'll take it to my indie to do whatever is required to get it running again.

As far as I know for the SDL at least their is only the standard plastic tank/aluminum core. However if you have time and want to get a better radiator try these guys:
http://www.wizardcooling.com/catalog/customer/home.php

Another member here had them make up a custom all aluminum radiator for $400 for his W123 300D. I was going to see if they could make one up for my SDL but my radiator started falling apart and I needed one asap.

Pete, you may also want to think about belt tensioner, idler pulley, etc. while you have the radiator out. Also be sure the vacuum pump is the new design with the screw heads sticking out and not the original which had a crimped-on cover. Be a good time to replace that, too.

FYI the vacuum pump is $339 at the dealer vs $341 online. I try to buy oe parts wherever possible so when I replace mine I will buy it from the dealer.

You're better off looking for a shorter belt. At the very least leave the refrigerant ports of the compressor sealed. AC system seals have to be lubricated every month or so or they dry up and leak. Running the AC keeps seals happy. Similarly with the AC compressor, if moisture gets to the innards, corrosion will start and in a year you'll need yet another compressor.

Sixto
95 S420
87 300SDL