On my 87 300D I just discovered a coolant leak from a little pump device that sits under the windshield washer reservoir. At first I thought it's for the washer fluid, but the stuff that's leaking from it isn't blue, it's mostly clear like my coolant. Is this the aux. water pump? Has anyone had success repairing it or does it need to be replaced?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

DieselAddict,

I have never had to dig one out, so I have never tried to repair one, but they are available from Fastlane. By the photo it does not look like it is repairable, but I am sure others with experience will pipe up soon. Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I've disconnected mine with no ill-effects so far. The aux. pumps are frequently cited as a cause of electronic failure in the climate control pushbutton units. I've heard of folks simply placing a short length of pipe in there and completely removing the offending item.

That's what I'd do in your case, but you could just spend the money and replace it too. Good luck...

Now there's an idea! What exactly is the pump's function? Does the AC and heater still work even with just a pipe there? That pump certainly isn't cheap, about $170.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I doubt A/C would be impacted, but my heater functions just fine without the pump. I've been told that its primary role is to boost heater performance during extended periods of idling, like when you're stuck in traffic. This isn't a problem for me out here in the boonies.

BTW on a related note: I recently replaced my mono-valve assembly and it boosted my heater performance at lower coolant temps--typically from startup to operating temps. The rubber bellows inside the valve had swelled and broken loose and was occluding the passage of coolant to the heater core.

I looked at it again tonight and realized that there's no need for a pipe. All I'd have to do is take that hose that runs from the pump to behind the firewall and connect it directly to the engine instead of the pump. Why use a pipe?

For some reason the leak isn't as bad now as yesterday and I haven't yet decided what to do. Completely eliminating the pump sounds fairly attractive, though I could buy the pump too, I'm not that poor.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The pump can be dismantled pretty easily but I doubt you can buy any of the parts you might need to rebuild it. It's probably worth a try though since it's sometimes amazing what a little JB Weld applied properly can do and if it's a simple leak you probably can seal it. Zietgeist is right though, the pump is to aid hot coolant circulation at idle so you can live without it if you're in a somewhat moderate climate or seldom in traffic. It has no effect whatsoever on summertime cooling. By the way, I replaced my pump by purchasing one on EBay. They don't come up very often but if you keep watching you might get lucky and find one.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

The electricals on my pump died so I unplugged it because it was causing the pushbutton unit to shut down. No leaks yet, though.

Without the pump operating heat at idle is noticably weaker. You can easily feel the air cool down at a stop sign, then warm back up while pulling away. I think the fan speed is also varied with heater core temperature, so the fan speed will ramp up and down as well. This could get a bit annoying.

I can live without the pump because I'm in Dallas and rarely spend much time stopped in traffic. If you live somewhere cold and/or drive in heavy stop-and-go traffic, then replacing the pump may be in the cards. You can always try it without and see if the result is acceptable.

- JimY

I ended up removing the pump and unscrewing the front cover. I found out it was the rubber gasket that was causing the leak. I applied some silicone on both sides, put it back together, let it dry overnight, then retorqued the cover and reinstalled the pump. At first the climate control buttons were screwy, most likely because of an air pocket, but after some driving all was good again and no more leaks! (knock on wood)

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

You need to be aware that when these go bad, they often draw more current. This additional current draw will often blow the Climate Control Unit which is much more expensive than the aux pump. So, for the short term, you need to unplug it and by pass it.

The pump should not draw more than 1.3 Amps.

To keep your car as it should be, you should replace it as soon as practical.

Good luck,

Larry, is there a way to test the current draw of the pump? What makes you think the pump is bad? I never had a problem with it, other than the leak which I just fixed, and the temporarily screwy climate control right after the replacement, but it works good now.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I don't doubt that a short in the pump can fry the CCU. I'm just wondering if it's really worth the money to buy a new pump as preventive maintenance. I did that with my vacuum pump, but there I felt it's worth it because a bad vacuum pump can do a lot more damage.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

This pump could fail in several ways. First, it can leak, you're already there. Make SURE it's the pump that's leaking, and not just a bad hose or loose hose clamp.

It also can fail by not pumping any more. You need to replace it under those circumstances.

Lastly it can fail by crudding up causing extra load on the pump motor. That's what will fry the CCU.

To check current draw it is no different than checking current draw on any other electrical component. Put an ammeter in series with the component.

The way I have done this is to disconnect the pump. Connect an ammeter to the positive battery post, the other side of the ammeter to the pump lead, and the other pump lead to ground. Then read the current on the ammeter. This will also tell you if the pump will run because you can hear it.

I would recommend that if the pump is leaking, replace it. But don't just replace it as a preventive maintenance item. It is easy enough to test or to see if the pump itself is leaking before you start shelling out the hard earned green backs.

Good luck,

Somehow I have the feeling that both of you didn't read the part of my post where I said that I fixed the leak. The leak is fixed! The leak is fixed! Do you copy?

Like I said the leak was from the gasket that seals the cover of the pump. Easy fix. The pump was clean on the inside. There was also a leak from one of the hoses, but that was not the only leak. After fixing & reinstalling the pump I drove the car for 50 miles and all is dry and the climate control works.

Dieseldiehard, don't bet anything. I'm one of those drivers who spends almost too much time watching the gauges. And I don't even listen to any music in the car, I just listen to the engine. The leak was pretty minor so the coolant loss was minimal. My car definitely didn't overheat.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Crap. The pump doesn't leak but it still sometimes interferes with the operation of the climate control buttons. It's time to get rid of it. I think I'll just run the car without any pump and see how well the heater works.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL