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  #1 (permalink)  
Old 10-21-2020, 09:42 AM
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Default Thread sealer on water pump bolts

On a 351W (stroked to 392 CID) Ford Racing Motor, which, if any, of the water pump bolts (standard rotation pump) require thread sealer? Of the eight fasteners that I removed (6 hex head and 2 allan head), there was no indication of any thread sealer previously used. Just wondering if that was a 'miss' or that none of these bolts threaded into water jackets, thus NOT requiring sealer.

Also, is it necessary to tighten the bolts on the back plate of these water pumps or do they already come tightly fastened? I've seen threads where the mechanic advises to LokTite and tighten the 4 backplate bolts.
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Old 10-21-2020, 10:49 AM
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Make sure the backing plate bolt heads to not come into contact with the timing cover when the pump is torqued down.
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Old 10-21-2020, 11:26 AM
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No thread sealant.

I also remove the backing plate and make sure the gasket has sealant on both sides, then tighten the bolts correctly.
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Old 10-21-2020, 02:56 PM
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Originally Posted by blykins View Post
No thread sealant.

I also remove the backing plate and make sure the gasket has sealant on both sides, then tighten the bolts correctly.
I installed a new w/p and after a week of driving, noticed a tiny drip of coolant at the bottom of the pump on the drivers side. Can't say for sure, but it appears to be coming from between the backing plate and w/p. I never took the backing plate off to add Permatex but the 4 fasteners holding the plate onto the w/p appeared to be tightened properly at the factory.

So the recommended step that I missed was to remove the backing plate and add Permatex to both sides of that gasket...and that is why I now have a leak??
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Old 10-21-2020, 03:09 PM
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Also, in which direction is the coolant flow on a CW rotation w/p? From passenger side head to drivers side head or vice versa?
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Old 10-21-2020, 03:33 PM
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Sounds like the backing plate was not tight. I use silicone on both sides of every gasket.
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Old 10-21-2020, 03:41 PM
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Originally Posted by SBSerpent View Post
Also, in which direction is the coolant flow on a CW rotation w/p? From passenger side head to drivers side head or vice versa?
No V8 goes from one head to the other.

The path is lower radiator hose to water pump inlet, pump outlets to each side of cylinder block, through each side of block, through rear of block up to rear of cylinder head, back through cylinder head from rear to front, exit both heads to intake manifold, thermostat housing, top hose, radiator, lower hose.
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Old 10-21-2020, 04:17 PM
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No V8 goes from one head to the other.

The path is lower radiator hose to water pump inlet, pump outlets to each side of cylinder block, through each side of block, through rear of block up to rear of cylinder head, back through cylinder from rear to front, exit both heads to intake manifold, thermostat housing, top hose, radiator, lower hose.
Yes, of course. Not sure as to what I was thinking.

So there is really no reason to suspect that going from the w/p inlet to the outlets that there would be a pressure differential between left side or right side entries into the block.
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Old 10-21-2020, 05:11 PM
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Yes, of course. Not sure as to what I was thinking.

So there is really no reason to suspect that going from the w/p inlet to the outlets that there would be a pressure differential between left side or right side entries into the block.
Unlikely, but depends what type of fault you could be chasing.

Pump rotation direction is dependant on impeller blade direction.
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Old 10-22-2020, 09:46 PM
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More thoughts on this topic. Steel backing plate on an aluminum water pump body. The CTE mismatch between dissimilar metals at high temperatures will create stress points where these two metals interact, which is at the gasket and the bolts between backing plate and water pump. Aluminum will expand and contract twice as much as steel for every degree of temperature change outside of room temperature. So I'm wondering whether this phenomenon is causing leaks at the gasket between the backing plate and the water pump.

The leak that I am seeing appears to be between the backing plate and the water pump. The leak didn't manifest until after a few hot cold cycles (i.e. a couple of trips in the Cobra over the course of a week or two).

Gonna remove the w/p and then remove the backing plate, replace the gasket and add gasket sealer on both sides of the gasket. Re-torque the backing plate bolts with LocTite and then re-attach the w/p to the block (using sealer on both sides of the w/p gasket). Hopefully this should solve all leak issues.

Last edited by SBSerpent; 10-23-2020 at 08:20 AM..
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Old 10-23-2020, 04:09 AM
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All aluminum water pumps have steel backing plates.

I've found loose bolts on the backing plates, no sealant, all kinds of stuff.
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Old 10-25-2020, 02:02 PM
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More thoughts on this topic. Steel backing plate on an aluminum water pump body. The CTE mismatch between dissimilar metals at high temperatures will create stress points where these two metals interact, which is at the gasket and the bolts between backing plate and water pump. Aluminum will expand and contract twice as much as steel for every degree of temperature change outside of room temperature. So I'm wondering whether this phenomenon is causing leaks at the gasket between the backing plate and the water pump.
1) yes, but aluminum heads are bolted to cast iron blocks. The coefficient of expansion is in inches of expansion per inch of length. A head is 4 or 5 times longer so it would grow 4 or 5 times as much. In short, a very short length of two metals is not much differential expansion.

2) Alloys of metals or specific types of metal can have huge differences in their thermal coefficient of expansion, within a type of metal. I do know from the design of trade secret part, that I legally cannot divulge, there is a specific aluminum and a specific stainless steel that has very similar coefficients of thermal expansion. Hopefully the engineers who design this stuff know some things.
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Old 11-03-2020, 07:21 AM
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No thread sealant.

I also remove the backing plate and make sure the gasket has sealant on both sides, then tighten the bolts correctly.
I have never seen this, but you guys like to make more work and reinvent the wheel.
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Old 11-03-2020, 07:28 AM
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I have never seen this, but you guys like to make more work and reinvent the wheel.
Build a couple hundred and you see all kinds of stuff.
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Old 11-03-2020, 02:34 PM
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I have never seen this, but you guys like to make more work and reinvent the wheel.
Reinvent the wheel?

Are you qualified to say that?

I have been in this game for 40 years, 40 hours a week. We see all sorts of stuff, lot's of "one-offs".
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Old 11-03-2020, 02:51 PM
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Reinvent the wheel?

Are you qualified to say that?
Yes...
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Old 11-03-2020, 02:53 PM
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Well I did make use of the advice and pulled the backing plate, replaced the gasket and added sealer and then re-torqued the 4 fasteners. Then applied sealant on both sides of the w/p to motor gasket and re-installed.

No leaks now!

FYI. When I pulled the backing plate off, I noticed evidence of coolant in a small machined cavity on the back of the pump housing that should NOT have had coolant. Clearly an indication that the 'dry' backing plate gasket by itself was not sealing properly.
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Old 11-03-2020, 02:57 PM
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Well I did make use of the advice and pulled the backing plate, replaced the gasket and added sealer and then re-torqued the 4 fasteners. Then applied sealant on both sides of the w/p to motor gasket and re-installed.

No leaks now!

FYI. When I pulled the backing plate off, I noticed evidence of coolant in a small machined cavity on the back of the pump housing that should NOT have had coolant. Clearly an indication that the 'dry' backing plate gasket by itself was not sealing properly.
And that shows the reason many of us use a sealant where some might not.
And not rushing produces less chance of a failure.
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Old 11-03-2020, 03:40 PM
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Reinvent the wheel?
I tried that a couple of times, but I could never figure out how to get rid of the corners... so I went back to the old fashioned wheel that was completely round.
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Old 11-03-2020, 03:59 PM
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And that shows the reason many of us use a sealant where some might not.
And not rushing produces less chance of a failure.
Exactly right. It's because of things like this that have bit us before, that we take time to check and double check, every. single. thing.
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