87’ OM603 water pump rebuildable?
 

Is there a way to rebuild the water pump on an 87’ 300D OM603? It has the metal impeller and it’s rusted because it sat with plain water in the system for a good while, before I got it.

I’m rebuilding the engine, I thought I read somewhere that the older water pumps can be rebuilt with a newer and better ‘plastic’ (for lack of proper word) instead of buying a new water pump.

I’m not trying to save money, if I can rebuild to original OEM water pump I’d prefer to do so rather than buy a replacement that isn’t OEM. From what I understand most of the replacement water pumps aren’t as good as the originals.

Cheers, Allen

Plastic is no good inside a coolant pump, the reason is if the engine overheats for any reason it will melt .If its got a plastic impeller dont buy it . If the pump change on your diesel is anything like the petrol w124 you will need to pull half the engine out to change it . I fitted a new Meyle pump to my engine and its working good after 4 years . Rebuilds can be done, but the cast will be much more than a new one . And you will have to wait for it to come back ,shiping cost + repair .

Don't waste your time rebuilding, you'll be the same amount of money in the hole as buying a quality replacement pump. Go with Graf or Laso (OEM suppliers) as they will have the cast iron impeller. Plastic impellers are inferior for a variety of reasons, not the least of which is their tendency to loosen up on the shaft and slip with age. If the coolant is kept up in the engine, the cast iron impeller will last for decades.

No point in fixing a water pump they're about 60 new for a graf on fcp euro I believe with lifetime warranty

Mercedes benz parts departments also used to sell rebuilt water pumps - as exchanged cores - the only catch was that your core should be an original part too.

I do not know about the 300D but on my '81 300SD it was a piece of cake changing out the water pump. Really easy.

I also think he is better off simply buying one. Then you also get a warranty.

However, I worked at a place where we rebuilt a lot of stuff including the Water Pumps on Diesel Engines.

You need a good hydraulic press that has good alignment to it.

You need something to hold the water pump body accurately otherwise stuff cracks. Sometimes the housing cracks and or bends. More so if the housing is aluminum.

Sometimes both or especially the impeller end of the Pump Shaft when the made it was pressed on and swelled to fill the Pulley and or Impeller . Not just press fitted together.

If you have no manual to it is possible you might not know which end you are supposed to press the bearing out of. Usually you press on the impeller end of the shaft and till the Impeller is stopped by the Housing then you continue to press the shaft/Bering out. However, depending how stuck the bearing is onto the shaft pressing it out can damage the Impeller and or the Housing.

On cars the bore the bearing goes in could be crimped over and if you try to press out the bearing you are going to ruin the housing.

They sell generic bearings and water pump seals but that does not mean the sell they sell metric or the type of seals in the original pump. A replacement seal has to take up nearly exactly the same amount of space as the old one did. If the seal is too wide when you press on the impeller you are going to crack it (that can happen any way if the impeller is pressed too far.).

The generic water pump shafts as far as length goes needs to be cut down and from what I have handled are not as good of quality as the originals.

Plastic impellers have been around for like 40 years. If they are made of the proper material you will have no issues.

Note the Water Pump on my 1953 Chevy Pick Up Truck was rebuilt by me a few times and I found the cheapie seals that came in the kits they used to sell wore out fast. I replaced that Seal with a Detroit Diesel Seal but I had to machine the sealing area in the pump housing deeper as the Detroit Diesel Seal was much wider.

I also once did a rebuild on the above with a Kit and the short story is that when the Engine got hot the Impeller was not turning. The fit on the shaft of the genric bearing was not tight enough. Punching dimples on the shaft and JB Weld worked to hold the impeller in place but of course there was the labor of having to do most of the job over again.

What's wrong with just replacing the water pump? You're better off putting the effort into upgrading to a water pump with a 72mm impeller.
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Just for grins and giggles, how about a head check? This is a $21 Gates pump for 602/603 from Rckato. The casting is quality aluminum, the impeller is cast steel, the bearing seems fine. What is wrong with just buying a part that works? You can buy four of these for the price of a magic German pump. If it lasts half as long, you've done twice as well.

Is that $21 pump from the rock made from the finest Chinesium from GongDung Province?

I read somewhere that you can't beat a genuine Mercedes water pump because they have the best impeller design. Even the companies that make them for Mercedes can't use this impeller design because of legal reasons, so they have to use an inferior design. Genuine Mercedes water pumps run ten degrees cooler or something.

Looking at tjts1's post above, the water pump on the right looks pretty good. I would assume the one on the left is factory, but don't know. I do notice that the impeller fins are curved in opposite directions of each other, which is strange...

Not sure about the earlier engines, but when I replaced the pump on my SDL earlier this year, the Graf pump I installed was identical in every way to the OEM MB-Star Laso that I pulled off. Same impeller design, same dimensions.

If that's the case, then there's probably no real reason to pay the extra money for genuine. It may depend on the engine type, though, as I've heard they can be different on genuine versus the same company that makes them for Mercedes. I'd certainly rather go with aftermarket if it had a better impeller design, which seems to be the case in tjts1's post.

"I've heard" and "Chinese crp" aren't evidence, not arguments. What else you got?



I manufacture cast and machined parts, and there's no obvious problem with materials or workmanship. The aluminum is first run, not recycled metal. The machine work is good quality. I can't see the bearing, but I won't accept comments about something that can't be inspected. If you have experience with bearing failures in Gates pumps, that's something else.

I am sure a gold plated impeller would work the best. How complicated is a impeller water pump? A bearing, impeller, casing, may be an o-ring. I would just buy a reasonable one and it will probably out last the car.