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. |
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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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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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?? |
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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Sounds like the backing plate was not tight. I use silicone on both sides of every gasket.
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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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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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Pump rotation direction is dependant on impeller blade direction. |
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. |
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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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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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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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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And not rushing produces less chance of a failure. |
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