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Old 08-01-2003, 04:27 AM
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Join Date: Oct 2001
Posts: 226
What is a "weep hole"

Was wondering what the water pump weep hole is and what its purpose is.

The coolant in my 96 c280 was belched out today. I parked the car and 45 minutes later noticed a long puddle of coolant by the car. The coolant overflow tank was empty and I noticed some of the coolant in a little catch basin under the water pump.

Any ideas on what the situation is? Filled it up with some water plus coolant and there is no further evidence of leakage after a couple of trips (total: 10 miles).
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Old 08-01-2003, 07:04 AM
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Join Date: Jan 2003
Location: Epsom Downs, England
Posts: 152
May just have got exceptionally hot and blew past the shaft seal.

It could be a one-off, but generally this is a warning of trouble to come...........

Keep a close eye on the temperature gauge and coolant level!
Paul Gibbons
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Old 08-01-2003, 08:09 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
That hole lets you know when the water pump is SHOT! You need a new pump.
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Old 08-01-2003, 11:24 AM
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Join Date: Oct 2001
Posts: 226
Ok, is a "weep" hole any hole that causes you to weep because it means you've sprung a leak somewhere or is there actually a design feature called a weep hole? If so, how does it work?
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Old 08-01-2003, 06:29 PM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
The weep hole is actually an intentional little hole in the w/p housing adjacent to the impeller shaft seal. If the coolant starts to "weep" past the seal, it exits through this hole. This is an indication to you that w/p seal failure may be imminent, although they will usually weep for a while before you get any serious leakage. But I wouldn't count on it.

Go ahead and replace your water pump at the first opportunity. Then as long as you've got the cooling system drained, you might want to consider changing to Evans waterless coolant. It's a non-aqueous propylene glycol coolant with a boiling point of 375 deg. F. That means it runs at essentially 0 psi, putting less stress on all parts of your cooling system, from radiator to hoses to pump to heater core. I put it in my '86 300E in July '02 and then loaded all four of us, our luggage and a 10' popup trailer and headed up to Anacortes, WA from So. Cal. The first thing we hit was the Grapevine at about 1 pm and over 100 deg. temps outside. The car never even thought about getting seriously overheated. As I recall, the temp guage hit 110 once on one of the steeper, longer inclines but it came right back down as soon as it leveled off a bit. I'm very impressed with the stuff. We put on over 2500 mi. during the trip and I've rolled up over 20k miles in the last year. I haven't had to add on ounce since I put it in, and I don't even worry about overheating in traffic at all. The only hassle is getting all of the remaining coolant/water out of your system, but it's really not that bad. I'll describe what I did, if you're interested. The coolant is about the same viscosity as MB coolant, so no changes are required to any part of your stock cooling system. The price is a little steep at about $25/gal., but considering that they claim you can leave it in there for 300-500k miles, I think that it's quite cost effective. Here's their web addy:

I know this may start a flurry of posts pro and con, but I'll be more than happy to answer anybody's question about my experience with the product.

disclaimer: I have absolutely no connection with Evans Cooling. I'm just a very satisfied user of their product.

Hope this helps


Last edited by Phalcon51; 08-01-2003 at 06:38 PM.
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Old 08-02-2003, 08:35 AM
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Join Date: Dec 2002
Location: Suburban NYC
Posts: 57
Where is it sold? I have never seen it. But I have replaced two radiators and two water pumps on 123s, all at the least convenient times and places. Anything that prolongs the life of the cooling system, not to mention the a/c, is worth $25 a gallon.
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Old 08-02-2003, 12:31 PM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
I'm in So. Cal., and I bought it at Mooneyes in Santa Fe Springs, 1-800-547-5422, They'll ship the product. There are also 4 suppliers out your way; Cartek, Inc. in Garwood, NJ, DY Trading in Maywood, NJ, Mack Boring and Parts Co. in Union, NJ and Enders Racing Engines in Phoenix, NY. The first 3 will ship. Here's the url for the suppliers page at Evans website that includes phone #'s:

BTW, when reading their tech info, don't confuse NPG with NPG+. The former is their original product that has a much higher viscosity that required a different water pump and larger diameter hoses and radiator to accommodate it. It was intended primarily for racing applications. NPG+ is pretty much a direct replacement for standard coolant and requires no changes other than flushing out the system and getting all of the old coolant/water mix out.

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