Help with water pump 71 280SL A/C

[Coochas]

I'm going to start off by saying that I'm just a weekend hacker of a mechanic.  My car is a 71 280SL with A/C.

I believe that my water pump may have a leak or at least its gasket.  When the car runs there was no coolant leaking but after turning it off, coolant begins to leak.  It seems to collect around the bottom of the crankshaft pulley. 

I decided to try to replace the water pump myself using info from this awesome site as well as a few books that I have.

I removed the hood for better access.
Many people recommend removing the radiator.  I removed all of the plumbing including the oil cooler.  I removed the radiator shroud.  I took out the four bolts that seem to hold the radiator in place.  Now the driver side of the radiator is free to move.  The passenger side is stuck.   I found that the bracket holding the AC to the radiator was fused to the radiator on top so I was able to free this up with a hammer and screwdriver.

The radiator seems to be stuck on the passenger side down low.  I feel like it is still attached to the AC but there is no obvious place that it is bolted.  I tried prying away the bracket which holds the AC to the radiator but it is still stuck.

ANY IDEAS??

Question 2:  I am having difficulty removing the fan assembly.  I removed the threehex bolts (one was missing!) which hold the blade to the viscous coupling but was unable to remove the fan.  Do I want to unbolt it where it attaches to the pullies? 

Sorry for the newby questions.  As I mentioned I am not the best mechanic but I do love to try to fix things!

[ja17]

Hello,
Don't hesitate to ask a lot of questions. With AC, this is a somewhat challenging job.  I remove the hood first also. Unfasten the fan shroud next. There are four 8mm hex head bolts holding it to the front of the radiator. A 8mm ratcheting box end wrench works best to unfasten these easily.  I unfasten the shroud then slide it back over the front of the engine and out of the way until the radiator is out. There are three 10mm bolts on the drivers side holding the radiator. One is below the battery tray. Remove it from below or take the tray out. There are two on the passenger side which are easily reached after the air cleaner canister is removed. Look for both coolant hose connections at the radiator passenger side lower and makes sure you have these both unhooked. Also be aware that the AC condenser is fastened to the radiator so the radiator and condenser must be removed as a unit. I suspect that the small metal AC pipe running between the condenser in the bumper and the condenser on the radiator is your problem. You need to unfasten this small metal AC line also. Then remove both the condenser and radiator together.
Removal of the fan blade is done by unfastening the four bolts going into the water pump/front pulley.  Normally these four have 10 mm bolt heads. The fan blade with fluid coupling are removed together as a unit. During re-assembly do not forget to stage the radiator shroud on the front of the engine before installing the radiator. You will need to remove the pulleys and belt before you see the five 10mm head hex bolts which hold the water pump in place. Going down to the block to replace the thermostat by-pass hose, water pump housing gasket, and or replacing the front crankshaft involves many hours of additional work since the AC compressor and bracket must be remove.

Get to the next step and ask more questions.

[Coochas]

Thank you so much.
I was planning on leaving the AC radiator part behind.
Are you saying that I should simply undo all of the AC lines from the top and bottom and remove it all together (i.e. attached to the radiator)?

[ja17]

Yes, that is the only way you can remove it. The condenser is attached to the side of the radiator with some tiny flat head screws. You cannot get to these screws with the radiator and condenser in the car. You have to pull both as an assembly.

[Coochas]

Yes, that is the only way you can remove it. The condenser is attached to the side of the radiator with some tiny flat head screws. You cannot get to these screws with the radiator and condenser in the car. You have to pull both as an assembly.

Thanks so much.  I spent about two hours stuck at this point!  Then again, I am enjoying getting back to working on cars!!!!  I'll post my progress this weekend.

[Coochas]

Thanks for all the guidance.
I disconnected the AC lines and was able to lower the radiator out through the bottom.
I was able to disconnect the viscous assembly from the pulleys and I can't imagine getting those bolts back on!
The water pump was unbolted but stuck in place.  I gave some love taps with a hammer and managed to get it off.  The 40 years old gasket was partially adhered to the water pump housing and I slowly and carefully removed it by scraping it off.
At this point I am certain that it was in fact the water pump that was leaking as the pulleys were full of coolant!

Question:  The inside of the pulleys had coolant and what looked like paste which I'm guessing was the coolant mixing with grease.  Is there any need to grease the inside of the triple pulley assembly?

Question:  I have found the alternator and power steering belts through pelican parts.  My car with AC also has two identical belts which wrap around 4 pulleys.  Can anyone tell me the common name for these belts or a part number?  I'd like to replace all the belts while everything is apart.

[mdsalemi]

Coochas,

Couple of things:

I did this in 2011, and like you, was very concerned I would not be able to get the viscous assembly bolts back on. Somehow with a bit of careful patience, it all worked. Have faith in yourself. Removing it all was just as challenging thus you are half way there.

Depending on what water pump you get, you should consider ordering a spare gasket ($3?) from MB. The gasket that came with my water pump was pretty thin; the MB gasket was far more substantial and worth the money.

Ask JA17 about the long versus short water pumps...I don't know if that makes a difference in your case with the a/c or not.

Good luck!

[Coochas]

Coochas,

Couple of things:

I did this in 2011, and like you, was very concerned I would not be able to get the viscous assembly bolts back on. Somehow with a bit of careful patience, it all worked. Have faith in yourself. Removing it all was just as challenging thus you are half way there.

Depending on what water pump you get, you should consider ordering a spare gasket ($3?) from MB. The gasket that came with my water pump was pretty thin; the MB gasket was far more substantial and worth the money.

Ask JA17 about the long versus short water pumps...I don't know if that makes a difference in your case with the a/c or not.

Good luck!

Thanks for the encouragement!  I bought a short pump which is the replacement one.  I've read a little about the longer one but can't imagine how it would fit!
I also bought a separate gasket for the pump from Pelican.  It looks pretty reasonable.
I'll try to be patient when it comes time to reassemble the coupling!

I'm going to drop the radiator off some time next week for pressure testing to make sure that it's OK.

[ja17]

When using the long pump you can delete the thick aluminum spacer inside the pulley. Then you use the prescribed four short bolts instead of the longer ones. Everything else remains the same.  Ends up being much easier to assemble without the spacer and without the long bolts. From an engineering point of view, I believe the long pump should be stronger.  Be aware that the 10mm head short water pump bolts are difficult to source these days.

If you use the short pump, you can use some masking tape on the side of the spacer/water pump to keep the bolt holes lined up during assembly. Don't forget to hang the fan shroud on the front of the engine before installing the radiator. You may no be able to get it in after the radiator is in place.

[Coochas]

Thanks again Joe.  I'm going to try to use the short pump since I already have the part in my greasy hands!  I'll try the masking tape on the inside and I'll definitely put the shroud on first (it was a bear to remove with the radiator in place).

Radiator hopefully will go out for testing this week.

[rb6667]

I feel your pain on this project.  Just like Michael, my hands were full trying to keep the bolts lined up in the correct position while trying to bolt the fan and clutch back up to the pump. Joe's suggestion to use masking tape is a good one.  I used some thin rubber bands wrapped around the spacer.  Once the bolts engaged with the pump, a quick snap broke the bands.  

 The next time the fan assembly is removed, the long pump will be used regardless if it needs replacing or not.  That short pump and spacer is just not worth messing with again in my book.

Only down side is finding the correct short 10mm bolts as Joe mentioned.  If you have some junkyards in your area, those short bolts were used on some Mercedes models in the 70's and 80's.





  

[Coochas]

Well the long pump is in and everything bolted back together nicely and the car doesn't leak any more!
I could not have done this repair without the knowledge collected on this forum.  Thanks to everyone who has contributed over the years.
I'd like to send a special public thanks to Joe Alexander for hooking me up with some 'short' bolts so I could do the longer pump conversion.  Frankly, I cannot imagine getting that short pump back together with those 'long' bolts!  I changed most of my hoses and did the belts while I was doing this job.

I took some nice pics of how to adjust the various belts (since I had asked the forum how to do it) and I'll post them when I have some time in an effort to give back to the forum.

THANKS EVERYONE!

[Garry]

Good to Hear Dave.

Please do the photos and a write up how and put them into the Tech Manual.  All Full Members can add to the Manual, you can practice in the sand pit before going live, and we rely on people like your self to do so for future reference for others.

Thanks
Garry

[66andBlue]

.....  Be aware that the 10mm head short water pump bolts are difficult to source these days.
....

These bolts might work for this: http://www.authenticclassics.com/Mercedes-N170a-Collar-Bolt-8-x-18-size-p/auth-006098.htm

[Benz Dr.]

I would recommend removing the whole AC unit unless you really want it in there. In my humble opinion, they cause more problems than they're worth. Overheating on a hot day, lack of proper air flow around the front of the engine,  and just try replacing that short hose between the thermostat and water pump housing without taking half the car apart to get at it. MB never really intended our cars to have AC like they did for sedans and they were usually dealer installed - ever one of them a mistake.

 Frankly, it's just about the worst thing you can do to your engine. I remove just about every one that I come in contact with. 


   ( running for cover now )