OM616 water pump questions - PeachParts Mercedes-Benz Forum

MagicBus · #1 09-30-2015, 10:51 AM

Hello, all

I did a search but couldn't find the info I was looking for. I'm doing the final push of repairs to get my 240D done and on the road.

While I have the radiator out and the front of the engine accessible, I'd like to replace the water pump, just for preventive reasons. I don't have any paperwork from the previous owner and don't know how old it is.

I've owned and driven W123s for almost 20 years, and do all my own repairs on all my cars (have done so for almost a decade now), but I still run into a lot of repairs on the W123 that are new to me. For example, I've done countless brake jobs on Subarus, my Volvo, and Volkswagens, but recently I did my first Mercedes brake job. Not all that different, but the brake pad pins were new to me, as was the front wheel bearing/hub/rotor setup.

As such, I've done plenty of water pump replacements on other cars, but not the Mercedes. What's puzzling me is exactly what and how much I'll need to remove. The idea of a separate water pump housing is new to me. It looks to me like I can just unbolt the pump itself from the housing and not disturb that. Am I wrong on this, or does the water pump housing need to come off the engine block?

At the moment, I have the pump accessible and the pulley off. It had a bunch or surface rust, so I cleaned it up and shot it with some fresh satin black paint.

leathermang · #2 09-30-2015, 11:25 AM

You have been working on MB Diesels for twenty years but do not own a Haynes MB diesel automotive repair manual ?
It has step by step procedure on pages 110 and 111 with good pictures.

mannys9130 · #3 09-30-2015, 11:51 AM

Yes, you can just unbolt the water pump from the block. Clean the mating surface really well of any debris left over, use a new unfolded gasket, and torque the bolts across from one another to the amount specified in the FSM. You definitely don't want to break the bolts off in the block.

If you haven't already gotten a new pump, go for one that's high quality. Don't use one with a plastic impeller, although a stamped steel one is OK and cast iron is preferred. Don't use anything such as Uro parts or similar.

leathermang · #4 09-30-2015, 12:05 PM

The balancer has to be rotated to provide access the lower bolt..
and be sure the engine is cold before pulling it...
to be safe clean the holes before putting bolts back in with a tap ... and use some kind of anti seize compound on the threads before reinstalling...

MagicBus · #5 09-30-2015, 12:43 PM

Quote:

Originally Posted by leathermang

You have been working on MB Diesels for twenty years but do not own a Haynes MB diesel automotive repair manual ?
It has step by step procedure on pages 110 and 111 with good pictures.

Actually, I've owned more than one copy over the years and read the procedure last night. The procedure itself suggested it was necessary to remove the crankshaft pulley and the water pump housing. From what I'm seeing, it looks like it should be possible to just unbolt the pump itself from the housing.

That's why I'm posting here - to cross check the Haynes against real-world experience.

Quote:

Originally Posted by mannys9130

Yes, you can just unbolt the water pump from the block. Clean the mating surface really well of any debris left over, use a new unfolded gasket, and torque the bolts across from one another to the amount specified in the FSM. You definitely don't want to break the bolts off in the block.

If you haven't already gotten a new pump, go for one that's high quality. Don't use one with a plastic impeller, although a stamped steel one is OK and cast iron is preferred. Don't use anything such as Uro parts or similar.

I did order one already - should have it in hand tomorrrow. If it looks suspect, I'll return it and order a better one.

Quote:

Originally Posted by leathermang

The balancer has to be rotated to provide access the lower bolt..
and be sure the engine is cold before pulling it...
to be safe clean the holes before putting bolts back in with a tap ... and use some kind of anti seize compound on the threads before reinstalling...

Well, the engine is at the same temperature as the atmosphere and will remain that way until it's all buttoned-up again.

As for the balancer, it looks like that's only in the way if I'm removing the water pump housing. Maybe I'm missing something, but I don't see why the housing needs to be removed from the engine.

mannys9130 · #6 09-30-2015, 12:50 PM

Taps are for cutting new threads. Chasers are for cleaning burrs and debris out of existing threads. Using a tap on old used threads is very harsh on them and can lead to damage.

leathermang · #7 09-30-2015, 12:55 PM

Lots of people have a set of taps... but not an extra set of chasers....
A tap will only remove corrosion or junk in the threads if it is the same pitch and percentage cut as the original holes are... use grease on the threads just like one would do with a glow plug hole and bring out often to clean the junk in the channels...

leathermang · #8 09-30-2015, 12:57 PM

Quote:

Originally Posted by MagicBus

Actually, I've owned more than one copy over the years and read the procedure last night. The procedure itself suggested it was necessary to remove the crankshaft pulley and the water pump housing. From what I'm seeing, it looks like it should be possible to just unbolt the pump itself from the housing.

That's why I'm posting here - to cross check the Haynes against real-world experience.

I did order one already - should have it in hand tomorrrow. If it looks suspect, I'll return it and order a better one.

Well, the engine is at the same temperature as the atmosphere and will remain that way until it's all buttoned-up again.

As for the balancer, it looks like that's only in the way if I'm removing the water pump housing. Maybe I'm missing something, but I don't see why the housing needs to be removed from the engine.

Looking at the whole system... it does not look like the housing has anything to do with removing the actual water pump.. The book had the warning about the engine not being hot ... unless you have a balancer without that cutout in the rim you do not need to remove it...
and .. what I am looking at and quoting from IS the Haynes manual....

MagicBus · #9 09-30-2015, 01:01 PM

Thanks for the additional input. I was going on my memory of what I'd read in the manual last night, but I haven't had much sleep in the past few days.

leathermang · #10 09-30-2015, 01:12 PM

Since you have the radiator out of the way... the only other trick is that to get the fan blade off you may need to grind the outer edge of a closed end wrench...

MagicBus · #11 09-30-2015, 01:39 PM

Quote:

Originally Posted by leathermang

Since you have the radiator out of the way... the only other trick is that to get the fan blade off you may need to grind the outer edge of a closed end wrench...

Fan blade is already off. It posed no problem whatsoever. I just unbolted it from the water pump with a standard 13mm socket on a 3/8" ratchet handle. Maybe 1 minute of work involved for that.

leathermang · #12 09-30-2015, 01:53 PM

The instructions in the manual were probably for people who had not removed the radiator... so they would not have room for a socket and ratchet.

MagicBus · #13 09-30-2015, 02:01 PM

That makes sense. I pulled the radiator and removed the fan blade so I'd have better access to the crank pulley to do the "2mm valve lift timing chain stretch" test. As I'm changing the coolant and the hoses anyway, it made sense to do that first.

jay_bob · #14 09-30-2015, 02:17 PM

Only thing I can add to this discussion is that it is very easy to break off one of the bolts when removing the pump. BTDT. Best course is to use a 1/4" drive ratchet and gently bump the end of the ratchet handle to break torque.

I would definitely get a new set of OE bolts from the dealer and not reuse the existing bolts.

If you do happen to break one off then it is not the end of the world, just tedious, to pull the whole housing off to either replace or clear out the old bolt. OM616 and OM617 (the 5-cylinder version found in the 300 series) share this same housing should you need to find a replacement in a junk yard.

Junkyarddawg · #15 09-30-2015, 03:03 PM

It's been a while since I did one but have probably done 100, at one time the replacement pumps came with new microencapsulated bolts in the box. I mention this because I seem to remember that one or more of the bolt holes pass into the water. If you reuse the bolts make sure to clean them and apply permatex aviation sealant or equivalent. This will prevent seepage past the threads and prevent seizure.