View Full Version : Water Pump Break-In

07-23-2012, 09:40 PM
Hey There,

One of the big three recommends letting the engine run for one minute before adding coolant to break-in the carbon faced pump seals. I believe this is to ensure they are fully bedded against the impeller and avoid coolant leaks.

Is it safe to run the engine with no coolant - even for one minute?


07-24-2012, 06:13 AM
Can't really say it"s safe but have done it may time myself (though not for water pump seals), with no apparent issues.

07-24-2012, 08:20 AM
I have never "broken in" a new pump seal. I have never had any issues with leakage...not ever. (except one "lifetime guaranteed" part that turned out not to have any seal at all installed!?!) I would think if some special procedure were needed, it would be included in an installation instruction with the pump.


07-26-2012, 05:03 PM
Any other thoughts or experience with breaking-in or not breaking-in a water pump?


07-26-2012, 06:21 PM
I've never heard of such a thing. I know on pool and spa pumps they use the same type of seal and the instructions on those say NEVER run dry.

Lou Metelko
07-26-2012, 07:59 PM
Back in 2003 when I threw one of those six vane "improved" pumps into the weeds, I ran the stock replacement pump for a minute at about 1,000 RPM before adding coolant. Don't remember where I heard or read that instruction but it was done on my TR2 and now at 30,000 miles later....

Lou Metelko
Auburn, Indiana

07-26-2012, 10:39 PM
Don't remember where I heard or read that instruction

Probably read it in the Moss catalog:

07-27-2012, 05:50 AM
Yep, that's the place

07-27-2012, 06:26 AM
Just don't do this with a ceramic based seal.

07-27-2012, 08:30 AM
Yeah, carbon seals were used into the fifties, but I don't believe any TR came with them, much less any replacement pumps. Phenolics have all but replaced carbon many years ago. As far as ceramics being used in water pump seals, those are used as a seal face for the phenolic part of the seal. Years ago, the cast iron of the impeller or the pump body itself (as in the original TR pumps)was the other mating surface. Sintered iron and other surfaces have also been used. I used to rebuild water pumps years ago, and if the mating surfaces are up to snuff, a dry spin up is unnecessary. Also, pump seals do drip on occasion, one of the reasons for the "weep" hole in all pumps. Newer style unitized seals have all but eliminated this, but they still have the holes so if the pump does leak, the coolant won't wash the grease out of the bearings. Original Chrysler slant six pumps had a trough to catch and channel away any drips so they wouldn't get on the fan belt causing slippage.

07-30-2012, 05:51 AM
Just as a follow-up, I decided NOT to perform the break-in procedure. I simply mount the belt and fired up the engine. All is well. Water pump is silent and performing its intended purpose. Nary a drip or leak after about 100 miles.