Thread: Water Pump Gasket Sealer

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Yeah, it was hard to tell from the picture, but basically, any bolt that goes into a water passage would need sealant.

Don

Don,
Got it back together, and no initial leaks so things are looking up!! I used the tried & true No 2 Permatex Non-Hardening Formula, and put it in all of the critical points.

Looking at your original pulleys and scaling from the pictures if I assume that the original crank pulley was 6" your water pump pulley scales to about 3 7/8" which is an overdrive ratio of right at 1.55 to one which is pretty severe - your water pump was cranking more than three revolutions for every 2 of the crank, or at 2000rpm your water pump was seeing 3100rpm. Not saying mine is good, but I'm overdriving 1.2 to one, so at 2000rpm (70+mph for me) my water pump is cranking 2400rpm. At my idle of 700rpm my water pump cranks 840rpm, which is not a bad thing. My stock 1990 F150 is at 1.35 with a 6.75" crank, 5" pump so logic tells me my setup should be OK, but time will tell.

I truly appreciate the link to the RunneRite products, and all of the input that everyone has provided.

No, they weren't that far off in size. The crank is about 6 inchse and the wp is about 4.5, but still enough to overdrive the wp quite a bit. It must have really been firing the water through the block, especially at 3000 rpms on the highway.

Don

I use the aviation sealer, the thick black brown stuff, seems similar to Permatex #1 hard set and #2 somewhat pliable. at any rate disassembley can be eased by coating one side, ex block, with a lite coat of oil then wiping off comes apart easley, learned my lesson the hard way no silicone on anything that can vibrate. Clean up of surfaces is simple with air powered 90* scotchbrite pads grinder.

Roger, the problem of the gasket potentially leaking due to excessive pressure is not the most serious concern. What IS a potential problem is that overspinning the pump can tear the impeller and diffuser plate apart. That is what came apart on me in Daytona and made such a racket I thought the engine had broken a rod.

The diffuser is only lightly spot welded onto each vane and it doesn't take a whole lot to break those welds loose. when that happens the pump is gone. Here are some pictures of the pump that ate itself up. At about $ 150 a pop it gets a little pricey, making a new set of pulleys at a couple hundred bucks not such a bad deal. My breakdown happened about 250 miles from home, and that kinda puts a damper on the day.

BTW, that cup shaped plate used to be a flat plate. Somehow it got deformed inside the pump and came out looking like that. This was a brand new pump with only about 250 miles on it.

Don

Don, I remember when you posted those photos before, after getting home and finding the problem, and I agree it's hard to imagine how that diffuser plate deformed like that. It had to be bouncing around like crazy, using the inside of the pump cavity as the dolly, and the noise?? I actually looked at the plate on mine yesterday, and especially at the spot welds but couldn't recall if you added a tack weld to your newest one or not. As you say, the spot welds are not real big, but then again how many pumps are out there doing just fine, and with varying degrees of overdrive from the factory? Just takes one, though, right? I also know it would be a real challenge to change mine without pulling the radiator & grille - might be done, but it'd be a task.

When I originally read Don's thread and with some interest, I was concerned that others might have the same problem. I wandered a Mustang forum, the Ford Truck as well as the Ford Muscle Forums (lurked, anyhow) but didn't find much in the way others who had had that problem. It almost appears that the Motorsport pump may be the culprit as I didn't see any others that had failures from over driving that pump. With the short radiator and possible filling problems and air bubbles, possibly those pump failures could be attributed to cavitation and heating of the the steel to weld failure, but not to the point of discoloring the base steel excessively. There are just too many that run those smaller pulleys without a problem.

Well, actually, Dave, I kinda created this problem myself. When I was putting the short pump assembly together I ran into the fact that Ford Racing had discontinued carrying the pulleys. I called around, trying to find some V belt pulleys to work. First stop was March Pulleys, they are right down the road from me in Naples, Fl. They were absolutely no help and were quite curt on the phone. Finally, I found that Zoops made pulleys for sbf, so I called them and got a crank and wp pulley they carried. The crank pulley didn't quite line up so I bought a Ford Racing spacer and had a machine shop modify my new Zoops pulley to fit it. Everything lined up and worked fine, except the ratio was off...........that was the problem I didn't forsee.

After 2 water pumps failed I decided to cure the problem once and for all, and that is when I learned that Runne Rite existed and had made the original pulleys for Ford Racing. Once I had those in hand I could see why I was having a problem, the ratio difference was so obvious. So, in fairness to Ford Racing, it was my choosing the wrong pulleys that caused the problems I was having.

Don

Don,
I have a theory that we may be both on the track. Your over driven pulleys are trying to move more water simply due to the fact that the impeller is moving at significantly higher speed. This in turn is creating water flow that can't move through the radiator fast enough. Your radiator is quite low which means that it may not totally flood the pump 100% of the time. Air bubbles are entrained in the water and cavitating in the water pump. This water is at the 180-190 degree operating temperature, but those bubbles are actually caused by the water boiling - and since it's under pressure and a 15 pound cap moves the boiling point to over 250 deg F and possibly (probably) even more in a localized area of higher pressure caused by that over driven water pump. Since your past life was with marine engines, think of an aluminum outboard prop that for some unknown reason shows erosion - that's often from cavitating. OK, now there are a couple problems - that pump is cavitating from being over driven then Ford and a less then satisfactory supplier, built a pump with crappy spot welds. Add that boiling water from cavitating, a poorly manufactured part and water, even not cavitating becomes almost a solid block when struck at speed (think of that last fall you took while water skiing- ouch!) and now you have a recipe for failure.

That makes a lot of sense to me, Dave. The pressures inside that pump must have been pretty high to deform the diffuser plate like that and to tear it loose from the vanes. I bet that sucker was spinning at 5,000 rpms when I was going down the road at 3,000 crank speed............and I had been going that speed for 5 hours or so on the way up to Daytona.
Don

Originally Posted by Itoldyouso

That makes a lot of sense to me, Dave. The pressures inside that pump must have been pretty high to deform the diffuser plate like that and to tear it loose from the vanes. I bet that sucker was spinning at 5,000 rpms when I was going down the road at 3,000 crank speed............and I had been going that speed for 5 hours or so on the way up to Daytona.
Don

I think Dave's analysis is a good one, and I had not considered the increased temperatures that would be present with cavitation, and both the higher temps and the forces of cavitation would be working on the spot welds. Also, a difference for me is the only time my engine sees 3000rpm is if I'm playing, and then it's not holding there for extended periods since 3000rpm in 5th gear equates to about 105mph for me.