Not getting much info on my other thread that I posted wondering what was leaking, now that I have found it, I am at a crossroads.

The very short coolant hose that runs from the thermostat area to the head is leaking on my 1988 300SEL. I have been told that the entire water pump has to come out in order to replace it and its not as simple as it looks to replace.

Has anyone been able to work wonders and be able to be so lucky to replace it without removing the water pump?

If not, what all has to be done in order to replace it? Any info anywhere on how to remove the water pump on this car/engine? If the water pump does have to come off to replace this, its a stupid design... almost as dumb as Lexus burying the starter under the intake on the LS400.

I really cant afford a costly repair now, since I have discovered that my Lexus may need a new power steering pump, so I am hoping this can be a cheap repair.

Thanks for any info.

Here's the FSM writeup on waterpump removal/installation.

Attached Files

20-2100.pdf (63.7 KB, 287 views)

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Yes, you can replace that hose without taking the water pump off. It is NOT easy but it can be done with some patience. I am sure that the mechanics on this list have done it many times. Be sure to clean off both pipes before putting the new hose on. Also, from the looks of your pictures, now would be a good time to replace that clamp, both of them. They don't last forever

Why is the hose leaking? are you sure that the metal pipe going into the head is not rotted out?. for a temporary "Ghetto" repair, you might try removing both hose clamps and wrapping the hose with good quality duct tape, and uses four clamps to secure/reinforce it. pure ghetto, but it may[or may not] buy you time.

where is it leaking from? Try tightening the hose clamps first and see if that helps.

You can replace the hosewithout removing the pump if you buy the mb part (not oem - too stiff), and you are very patient about working the hose through the narrow gap with blunt tools. There isn't much room but a couple people have been able to do it. Replace both hose clamps, and be aware that all that trauma to the hose will probably shorten its life.

Another option is taking a hacksaw to one of the pipes and cutting off a quarter inch or so to give yourself more room. Be sure not to let any filings into the water passages (!).

Finally, the water pump r&r isn't too bad, it just takes a lot of time. If the belt has to come off, be prepared to replace the belt tensioner.

I saw the other thread and considering the quite broad nature of the question, I thought the responses were very helpful to guide you to looking at the right places to find the leak.
To do it right the water pump needs to come out to replace it. It's a job that requires a little competency and expect to run into [at least minor] problems while doing so. It's one of those jobs that will have you cursing out mercedes, but once you've finished you'll be saying it wasn't really that bad and it would take you a quarter of the time next time you do it.
These hose don't usually go "bad" but can develop leaks so if you're looking for a temporary solution, I agree with workerunit and tighten/readjust/add clamps. Carefully "feel" the hose to see where the nipple ends. The nipple coming out of the head extends to within about a 1/4" of the outlet on the pump, so you should have enough room to set another clamp on the pump side of rusty one in your picture. There is a flare on the end of the pump outlet and that clamp usually rests right up against the flare, but that side is probably sealed okay. You also have enough hose on the head side of the rusty clamp that you might be able to add a clamp there as well. The nipple is pretty heavy gauge so I doubt it's rusted through, but it may be pitted. As said this is an ATTEMPT at a temporary solution. Since your leak is minor, this is probably all you'd need to get you by for a while.
As far as being able to put a new hose on without removing the pump, I'd say it's very doubtful and if possible it might totally depend on how much space there is between the nipple and the pump outlet, which, while it may vary some, it's usually only about a 1/4". I tried (for the hell of it) to do it when I did my head gasket and found that for all the trouble I was having to manage it (if it would have ultimately even been possible) I'd just a soon take the pump off. One of the big problems, even if you can get the hose on part way is that you'd need to slide it all the back onto one side or the other to get the hose fully on through the narrow gap and then slide it onto the other side. The problem is, the pump outlet is too short (and wider than the nipple side) to slide on that side first. The nipple is long enough but the intake manifold is too close to it to allow the hose to slide back much further than it is sitting right now.
I thought about cutting the nipple shorter when I had the head off to facilitate being able to do this later, but I concluded that these hoses almost never go bad and taking the pump off isn't that big a deal once you know how to do it. If they do develop a leak, readjusting/tightening the clamps should take care of it.
Just my opinions.

Edited to add: anthonyb is correct, the MB hose is somewhat thinner walled than the aftermarket hose (at least the ones I got). And you are likely to need a new belt tensioner, they're not a longevity part.

Thanks for ALL of the replies.

I am not sure why its leaking... maybe because its almost 22 years old. Not sure if its ever been changed.

To answer someone else question, its actually leaking on the right hand side (not the side that looks rusty). I felt under the hose and the coolant leaking was on that side.

I really cant afford a costly repair now by having the pump removed/replaced, and I am not mechanically inclined, so I think I will take a trip down to my Mercedes dealer tomorrow and get the hose I need and attempt to change it. I just hope I dont get the old one off and cant get the new one on! That would be bad! We tried tightening the clamps, but they would not budge. I hope I can just get them off.

I know a mechanic that works on cars, (mostly European cars), so I am sure he could do it easy. I may see if he will change it for me. Be a good time to get that green coolant out too, but that may have to wait a couple of weeks.

Thanks again.

To get the old hose off, it'll have to be cut off. Once it's cut off, you ARE committed. I'd say it's nearly a sure bet that you (or your mechanic) won't be able to wrangle a new hose on it without taking the pump off. Expect at least a $150 bill for taking the pump off to do the job (if you won't need a new belt tensioner, add about $125 more if you do).
No offense, but if your stuck just trying to loosen the clamps you're probably not a candidate to remove the pump yourself, so I'd get the mechanic and instruct him that you only want to try and remove the clamps, possibly reposition/rotate the hose and put new clamps on it (and get that antifreeze changed). See if that works before proceeding any further.

as federman said, use some PBlaster or any other rust-eating lubricant. loosen the clamp closer to the head and move it a bit forward towards the head..that would be the first thing i do before removing that hose and discovering that i have to remove the pump to put a new one in.....

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1993 300E, 2.8 M104 .....

QUOTE: "To answer someone else question, its actually leaking on the right hand side (not the side that looks rusty). I felt under the hose and the coolant leaking was on that side. "

If you think it's leaking from the water pump side of the hose the same advise applies. Loosen the clamp, resetting it in a slightly different position, to the right or left if possible (doesn't look like there's too much discretion there though) and retighten it. Maybe a good idea to replace the clamp. The aftermarket clamps are a little wider than the thin MB clamps which would give a little more bite which might help.

Something else to consider, the cover on top of the pump right next to that hose is the thermostat housing cover. They have a large o-ring for a gasket and are known to leak with age. It's possible that it could be the source of the leak, that is, it may be leaking at a point very close to the short hose and running down around the outlet by the lip of the hose, making it appear that the hose is the culprit. If further inspection reveals that that may be the source, the o-ring is very easy to replace.
Note though, that tightening down on the three bolts on that cover will NOT stop any leak there. Once the cover is clamped down on the o-ring, the cover and pump are now metal to metal and further tightening only risks stripping the threads, it can't squeeze the o-ring any more.

I could not agree more, It will be almost impossible to replace that hose without removing the water pump, if you are going to remove the water pump, you might as well replace it as well, you will certainly need to replace the waterpump to block o-ring if nothing elase. The t/stat and o-rings can and do fail, replacing the t/stat and o-ring is a easy job.

even better, don't touch the existing clamps, just buy two more clamps. loosen them all the way (the come apart), and install them on the outer edges of the hose (towards the head and the thermostat housing)......if that does not fix it then you will need to replace it, but this will cost you $5 as apposed to a water pump job....

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1993 300E, 2.8 M104 .....

Thanks for the replies and that info! OK, I will try that. I will not be using the car again until next Sunday, so I will spray some PB blaster or WD-40 on those clamps and see if we can retighten them.

If not, couldnt I just buy more clamps and put on each end? I am not sure how these MB clamps work, as to whether I can put a new clamp on without removing the hose.

It would definitely be nice if I could indeed stop this leak without even having to replace the hose. The hose really dont look that bad.

Thanks again.

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2004 Toyota Sequoia Limited 4wd
1991 Lincoln Town Car Executive
1991 Cadillac Sedan DeVille
1988 Mercedes 300SEL
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville
(Prior MB's: 1974 240D, 1985 380SE, 1984 190D, 1993 400SEL)

Thanks. I did get new clamps from Advance auto parts as recommended, but I only removed the one on the side that was leaking. The hose is so short, I was not able to get another clamp on the end of the hose, so I had to remove that one.

It seems to have stopped... I will know more next time I drive it, but I am having rear brakes issues now, so not sure when I can drive it again.

The hose did seem to move up in the middle with the new clamp on... hopefully it wont burst.

you will find that I did replace the hose without removing the water pump. It is NOT going to be easy but, it is possible. Keep in mind, as mentioned before, once you remove/cut the hose, you are committed to finish the job and yes, get the MB hose.
You decide. Either way, good luck!

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J.H.
'86 300E