Came out of work yesterday and saw a big puddle of coolant under the front end of my truck. After spending a couple of minutes looking around under the hood and front end I could see that it was dripping from the underside of the harmonic balancer. A little more looking and it seems like it might be coming from the underside of the water pump - maybe somewhere towards the driver's side.

Here's the bizzare part. When I filled it back up with water (6 quarts) and started it up, the leak seemed to stop almost instantly. I drove it 40 miles and stopped several times on the way home. No signs of leaks. After I got it home and parked, it still wasn't leaking. BUT, when I came out and checked it after it had been sitting for about 5-6 hours and cooled down, it was leaking again! A steady drip...drip...drip from the bottom of the harmonic balancer just like before.

So what is up with that? I have never seen an engine leak when sitting cold but NOT leak when running and warm before. Usually when they warm up and the coolant pressure rises, they leak worse. In my experience they always leak worse when running than when they aren't running - due to the pressure created by the water pump.

Anybody ever seen anything like this? My first thought is that maybe it is leaking on the suction side of the water pump where it bolts to the block. Where are the suction ports on the whater pump? Top? Bottom? Passenger side? Driver's side? Any other ideas/theories?

 

Hi CheaperJeeper,there is a weep hole on the water pump. I think the water pump seal is shot. I'd say a new water pump will be the cure. It will just keep getting worse.

Norm

 

Yeah, I'm thinking the same - just never seen one leak when cold and NOT under pressure - but stop leaking when warm and under pressure. Just strikes me as bass-ackwards.

I've gotten feedback elsewhere to indicate it isn't uncommon for diesels to act like that though....

 

How hard is it to change the water pump on a 6.9? What all do you have to take off to get to it (besides the belts of course)?

 

My 86 6.9 leaked just like yours.You need to take all the brackets that are connected to the water pump off.Another arm would help but you can do it.you need to have it pretty clear to get the gasket on real good.You don't want to do it twice. good luck.

Norm

 

Autozone had reman pumps for $26 bucks. Anybody had good/bad experience with their reman stuff?

 

Might want to call around and find who sells new and get a new part..... most remans are ok but you don't find out until after the fact. I will email/PM you.

 

Jeep, Cold water leaks are common on road tractors and equipment. I have seen water pumps do this.

Most cold water leaks on road tractors are from silicone hoses. The hoses will last forever but they require a "constant torque" or a lined clamp.

 

^^^ I agree. I've had trucks lose water where I couldn't locate a leak. Pressurize the system... NOTHING. Let them sit over a long weekend and they flow like the water works.

I would go with a new water pump. The attention to detail isn't there with rebuilds and I've seen them fail more than not. Most of the reputable parts houses around here don't even stock remans anymore. The price difference and the warranty hassle isn't worth the trouble.

Jason

 

Funny thing is I had a mystery leak like that a couple years ago at the front of the engine. First my Dad's 6.5 started a leak, so I replaced the water pump. Then then a week later, mine wanted attention and it developed a leak at the exact same place. I replaced the gasket on mine and reused the pump.

We've kept the two trucks separated ever since and no such leaks have returned. LOL In both cases the water pump gasket simply let go.

On a more serious note, you are making a lot more pressure in the cooling system when the engine first starts up cold. I think that could put more pressure on whatever leak you have. Unlike oil, coolant viscosity doesn't really reduce as it heats up so in this case a hot engine is less likely to leak a visible amount of coolant than a cold one (parts heat up and expand, potentially reducing the size of a leak). You are probably still loosing some coolant while driving it, but its a smaller amount and what does leak just gets cooked off before it has a chance to drip.

You are going to take nearly all the accessories and related brackets off the front of the engine to get at the water pump. Its not a really nasty job, but its not that fun either. I've only had to do it once on my truck and it was a 2 day job for me. You need to pay attention to the bolt lengths of the pump bolts as there are differences and if you put one thats too long in the wrong place, it could reach the camshaft gear. That would be very bad karma. Bear that in mind of you have to replace any of the bolts - make sure they are the exact same length as the originals.

 

I tell you an odd one. I have seen two 60 series Detroits have water pump failures and fill the crankcase full of coolant. Both cases were trucks that sat for awhile. Mud Dobbers built homes in the casting hole "weep hole" on the pump. Coolant couldn't get out so it went in the crankcase through the oil seal.

 

The biggest thing on the water pump is the fan clutch the nut is left hand thread and it is easier to remove it before you remove the belts. The last one I changed was in december in a wallmart parking lot (about three hours).

 

Three hours in a WalMart parking lot, now that does not sound like fun at all.

I lost a lift pump this winter at the mall as we finished plowing snow..
I opted to haul the truck back to the shop to change it instead of trying it in the mall parking lot, which is on top of a hill.

With the way the wind starting blowing just about the time I would have the old one off, I was glad I took it to the shop, even though that was a 30 minute job.

 

You had me at 3 hours at wallmart........

I hate having to tow an injured vehicle home if its not under its own power, but it usually better for you and the vehicle.

None of my trucks have ever done that to me though. Guess I'm just lucky that way. Even when I blew out the overdrive section in my transmission, it limped home in second gear.

 

Well, for anyone interested, I pulled the water pump today (after using my dental mirror to verify that water was dripping off the snout of the pump onto the harmonic balancer).

Sure enough, there was a nice telltale rust track from the weep hole to the bottom edge of the pump casting. So I guess I found my leak.

BTW, the reman impeller looked exactly like the impeller in the one I pulled off.

To make sure I didn't mix up any of the bolts I laid the new water pump on top of a cardboard box, traced the outline, and used a phillips screwdriver to punch holes through the boxtop where each bolt hole was. Then I put the bolts into the holes in my newly-made "template" as I pulled them out.