Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 07-05-2003, 05:27 PM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,503
Can't Get M104 Water Pump to Seal

I recently changed out the water pump on my m104 engined 1993 300E. It looks like I get to have the joy of doing it again. It appears to be leaking at the water pump to block connection. This joint is sealed by an o-ring in the pump.

When installing I used a new o-ring, lubed it just bit, cleaned up the block, and tightened the water pump to torque specs. It stays dry when the engine is cold, but leaks under pressure.

Any thoughts on how to make sure this doesn't happen again? There was a bit of rust on the engine block around the water pump fitting, perhaps that was the problem? If so, how should the engine block be cleaned and prepped? I'm assuming the use of RTV style sealants is not a good solution. Frankly, I'm a bit baffled, as there's not much to go wrong here.

- JimY
Reply With Quote
  #2  
Old 07-06-2003, 11:30 AM
JetForeman
Guest
 
Posts: n/a
Jim, you probably won't know exactly what happened until you take it apart. Things like a cut o-ring, dirt, debris, rust, and etc. can definitely cause it to leak.

When I replaced mine I put just a small bead of black RTV in the o-ring channel to keep the o-ring in place during assembly. Make sure it is painfully clean before assembly and take your time.

Good Luck
Reply With Quote
  #3  
Old 07-06-2003, 06:41 PM
Registered User
 
Join Date: Feb 2001
Location: Colleyville, TX
Posts: 229
FYI.. I replaced my water pump last week and I used some Acetone /Laquer Thinner to clean the mating surfaces thoroughly. Still some of the grout wouldn't come out so I used sand paper to get it out. I spread a thin bead of clear RTV Silicone sealant on the pump surface before bolting it back. I let it cure overnight and added coolant the next day. I have driven the car for over a week and so far no problems. Hope this helps

smk_texas
93 400e
86 BMW 325 e
Reply With Quote
  #4  
Old 07-06-2003, 06:52 PM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,503
Thanks for the input, guys. I think where I went wrong was in not cleaning up the engine block aggressively enough. I think something like a kitchen scrunge or fine grit sandpaper is in order. Next time I'll remove anything that looks like scale or corrosion until the mating surface is bright, shiny metal. That's what I want, yes?

- JimY
Reply With Quote
  #5  
Old 07-06-2003, 07:07 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Some wheel bearing grease to keep the o-ring in place won't hurt a thing -- I'm leary of RTV in case it hardens too much while you are installing, causing a small void somewhere or over crushing the o-ring.

Make SURE the slot for the o-ring and the face it seals on are completely clean and smooth -- doesn't take much of a rouch spot to leak.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #6  
Old 09-18-2003, 11:58 AM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,503
Update. Last night I pulled the water pump. No obvious cause for the leak - the o-ring was well seated, not pinched or cut. I cleaned up the block mating surface using a nylon kitchen thingie, followed by some metal polish. The mating surface is mostly bright, shiny metal, with a few discolored areas. I can't detect any roughness in the surface, nothing you can catch a fingernail on.

Put it all back together. Used a new o-ring, of course. Result: It leaks about 10 times worse than before.

If I had any hair left, I'd pull it out.

I'm gonna try this one more time. I've been lubing the o-ring with grease. This time I'm going to put it in dry. If that doesn't work, I'm either taking it to my mechanic or driving it into a lake, I haven't decided which.

- JimY
Reply With Quote
  #7  
Old 09-18-2003, 01:24 PM
jbaj007's Avatar
Registered User
 
Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
Double check the water pump flange for a hairline crack. If it's a rebuilt (even MB), it could have been over tightened in it's previous life, micro-cracked, and not picked up in the rebuild process.
__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
Reply With Quote
  #8  
Old 09-18-2003, 01:30 PM
haasman's Avatar
Registered User
 
Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,097
Sorry to hear about your redundant training in water pump R&R-

Check to see if the pump mating surface is really flat. Try using a steel edge ruler, moving all over the surface. Look carefully for any light gaps.

Is it the correct O-ring? If you still have the old O-ring match it up. Compare for the obvious overall diameter but also thickness.

Where did you get it and the pump?

Haasman
__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
Reply With Quote
  #9  
Old 09-18-2003, 01:41 PM
benzfan's Avatar
Registered User
 
Join Date: May 2001
Location: Toronto
Posts: 277
I'm surprised nobody has mentioned the obvious; When replacing the pump, treat the snugging of the bolts the way you would on a cylinder head or wheel. Tighten in increments only and make sure you are tightening them evenly all the way around. It doesn't take much to get it slightly 'cockeyed' and then the O-ring will not crush properly and evenly all the way around.
Reply With Quote
  #10  
Old 09-18-2003, 03:33 PM
Registered User
 
Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
I agree with Benzfan; incremental tightening is important on any flanged connection. If one corner is tightened just a little too much initially, it will cock the water pump slightly because of the o-ring. When you tighten the opposite corner it may cause the flange to "bow" slightly, leaving an area of decreased pressure between the bolts. Under pressure this could cause a leak.

When I replaced my water pump recently, I used a medium coarse (80 grit) 6" long sharpening stone (with some light oil to prevent clogging the stone) to flatten the mounting surface on the block. Not really much chance of warpage here, but it helps to get the crud off and ensures a flat surface if you do it carefully.

I used a new pump, but checked the surface nonetheless to make sure it was flat. Then, I just put 4 tiny dabs of wheel bearing grease in the channel where the o-ring goes to hold it in place. Still, it's important to make sure that once you set the pump and o-ring against the block, try not to move it at all while you run in at least two of the bolts. Screw them in till they just touch. After you get all 4 in, finger tighten them lightly in a cross pattern. If you can, get a torque wrench that reads down to 5 lbs and tighten them in 5 lb increments in the same cross pattern till you get to the 15-17 lb./ft.

Good luck with it.

Gary
Reply With Quote
  #11  
Old 09-18-2003, 03:49 PM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,503
Thanks for the support, moral and otherwise.

The pump is new, not reman. I sourced it from my usual supplier - Rusty Cullens. He sells out of the Worldpac catalog, so it's the same stuff available via Fastlane. I forget whether the pump is Laso or Graf.

I too am beginning to wonder if the pump is defective. I'll check more closely when I pull it out again. Will examine for cracks, defects, and flatness of the mating surface.

I'm very much aligned with all the advice given here. The pump has dowel sleeves on the holes which allow it to hang in place before any bolts are inserted. Hence there is very little movement or disturbance to the o-ring. I'm tightening the bolts in steps, and not overtightening. (A torque wrench isn't accurate when using a swivel joint, plus one of the bolts on the m104 requires use of a standard allen key - no room for a socket, with or without swivel, FLX13, or whatever.)

On the plus side, I'm getting really good at this job. And I replaced the broken tensioner adjustment bolt thingie. So we're making progress on the little things, just not the big things.

- JimY

'93 300E 2.8 91K (dead)
'87 300TD 132K (alive)
'98 E300 54K (gone)
Reply With Quote
  #12  
Old 09-18-2003, 07:48 PM
Registered User
 
Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
First, Why not buy from us if you use us for tech help for free

That said, you may also want to look at the small hose on top of the water pump. I have had them leak and run down the block.

Also, the aftermarket pumps aren't that great. I would use an OE reman if I had trouble.

Good luck.

Ps TRY PHIL 1-888-333-4642
__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS
Reply With Quote
  #13  
Old 09-18-2003, 08:56 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Check the O-ring slot for porosity and/or rough spots. Any deep scoring, etc in the slot can keep the O-ring from sealing. Some wheel bearing grease won't hurt, either, to fill any shallow irregularities.

Make sure the O-ring protrudes sufficiently from the slot when installed, too. If it doesn't crush enough, you won't get a good seal.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #14  
Old 09-19-2003, 09:33 PM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,503
Update. Pulled the water pump again Thursday night. (Wife is out of town, can tinker on cars every night. Is this good or bad?) I'm getting better every time - 50 minutes from a complete car to having the pump on the bench.

Checked the mating surfaces; they looked good. Cleaned everything up with a degreaser, removed all traces of grease from the pump, flange, and o-ring. Put it back together dry. It was perfect, right from the start. My problem was too much grease - it doesn't take much to cause a problem.

The shop manual doesn't say to use grease or anything else. Given the snug fit of the o-ring in the water pump, I think that's the thing to do.

Gotta love that hard earned success.

- JimY
Reply With Quote
  #15  
Old 09-19-2003, 10:05 PM
I told you so!
 
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,791
Thanks for sharing that with us, Jim. When I did my water pump and cooling system, I took things apart and found RTV at a lot of the seals. I cleaned off the RTV and dressed the mating surfaces, scraping everything off, finishing with scotchbrite. I then put a thin coat of silicone on the o-rings, nothing else. Just enough to make them shine. I don't like installing seals dry. I learned as a kid reading Machine Design that some pressurized joints require o-rings to slide into a certain position within the groove for proper sealing (not that cooling systems are highly pressurized). I figure the silicone would allow the o-ring to relax into it's natural position.
__________________
95 E320 Cabriolet, 140K
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 01:13 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page