351W water pump gasket failure

[BB767]

This is not a car question but many of you have a similar engine so I am hoping someone may have an answer.

Blueprint 351W based 427. Cruising down the road when coolant starts gushing out. Pull over and coolant is flowing from the drain slot in the water pump mounting plate (the one that actually bolts to the block behind the water pump that the water pump is bolted to.) Tow it home, tear down water pump, and......... nothing! Everything looks fine! We had refilled the coolant (with water) when it was up on the jack stands and confirmed the location of the leak, the rear of the water pump. But when inspected it all looked normal. We had torn the gasket while removing the pump so could not ascertain its original condition. All we could guess was that the gasket had blown out (water flow was pretty substantial) and allowed water to leak into the back of the pump mounting plate and out the drain slot. This was only a theory but there was no other explanation. Cleaned everything up and put it back together. Everything is fine, not a drop of water leaking anywhere.

So, the question is, does anyone have any experience with a water pump gasket just blowing out for no reason? Why would this happen? How can I prevent it from happening again?

Engine did not overheat. Thermostat (180) seemed to be working as we had driven for about 45 minutes prior with no problem. Thermostat works fine now (after the fix). 20 psi pressure cap felt like it was working OK but replaced it just to be safe. I would rather not have this reoccur, but I have no clue why it happened!

If you are not familiar with the water pump I am talking about please do not ask me to explain the assembly. There is a backing plate with bolts that are inaccessible when the pump is mounted. If these are the cause of a leak the pump must be removed to tighten them. And if it leaks in certain positions on the pump, the fluid flows into a chamber behind the pump itself, which is what mine did. As far as I am concerned it is a goofy design, but it is what is on the engine (and thousands of others) so I have to deal with it.

Anyway, thanks for any advice you may be able to give.

[cv2065]

Interesting thread about this from Jalopy Journal a few years back. Not sure how much applies, but take a read.

https://www.jalopyjournal.com/forum/threads/351w-water-pump-gasket-keeps-blowing.586644/

[BB767]

Interesting thread about this from Jalopy Journal a few years back. Not sure how much applies, but take a read.

https://www.jalopyjournal.com/forum/threads/351w-water-pump-gasket-keeps-blowing.586644/

Great information, thanks! Went right out and checked, my crank pulley is a little larger than the water pump pulley. Could be a contributing factor, I'll discuss this with Blue Print.

[BadAsp427]

I'm surprised you have a 20psi cap... FFR sent included a 16psi cap from. I've never heard of a street engine needing 20psi... In fact, I was surprised when I looked at my FF supplied cap and it was not a 14psi cap... Just a thought, perhaps you have an over pressure problem... I'll be watching for your final determination.

[BB767]

I'm surprised you have a 20psi cap... FFR sent included a 16psi cap from. I've never heard of a street engine needing 20psi... In fact, I was surprised when I looked at my FF supplied cap and it was not a 14psi cap... Just a thought, perhaps you have an over pressure problem... I'll be watching for your final determination.

I was wondering if anyone would question that. The upper tube is from breeze but I am pretty sure the cap is the one that came from FFR. When I went to Auto Zone to replace it they said the cap should be 13 (for the Mustang 351W) so that is what I put back on it as a precaution, I can always change it back. However, should even 20 psi be enough to blow out a gasket that is properly torqued with adhesive sealer on it?

[Vspeeds]

That water pump sure has been giving you problems. If you need a hand with anything, please call and I'll shoot up there to help.

[GoDadGo]

While we all know that I know very little about Fords, I do know something about water leaks.
With that said I'm going to "Parrot This Cause" and also think that the 20-pound cap was a contributing factor.
Good Luck & I Hope You've Overcome This Bump/Leak In The Road!

[CraigS]

Did you remove those thin head bolts so you could remove the back plate and use sealer on it's gasket? I don't have the answer on this but I do remember that the gasket set I bought for my 351 had 3 or more gaskets for the pump. They are just slightly different and it took me a while to decide which to use.

[Murd]

I assume this water pump came installed from blueprint?
I have a 302 but same pump/timing cover. If it’s leaking out the drain slot that is from the pump backing plate to timing cover connection. I had the same problem with my first water pump,tried 3 or 4 times re installing and leaked everytime.

When you remove the backing plate, are the water ports on the pump casting enclosed? Ie is there aluminum casting to support the plate around the water port holes on the back plate?
My first one did not have this, and that’s where it would leak, water ports to inside of timing cover. This is because the back plate had no support and didn’t push tight to the timing cover.

Replaced with a flowkooler water pump that had this extra casting and extra bolt holes that matched my timing cover and it worked first try.

Good luck!

[BB767]

I assume this water pump came installed from blueprint?
I have a 302 but same pump/timing cover. If it’s leaking out the drain slot that is from the pump backing plate to timing cover connection. I had the same problem with my first water pump,tried 3 or 4 times re installing and leaked everytime.

When you remove the backing plate, are the water ports on the pump casting enclosed? Ie is there aluminum casting to support the plate around the water port holes on the back plate?
My first one did not have this, and that’s where it would leak, water ports to inside of timing cover. This is because the back plate had no support and didn’t push tight to the timing cover.

Replaced with a flowkooler water pump that had this extra casting and extra bolt holes that matched my timing cover and it worked first try.

Good luck!

Thanks Murd, more great information. Spent the last hour comparing pumps, I see what you mean. If this happens again I will get one of those pumps. It did take three tries to get it to seal the the first time (the pump has been replaced before), but this time not a drop on the first try.

[BB767]

Hey Craig, thanks for the input, it has been replaced before so I have figured out what you are referring to. Mine had extra gaskets as well.
Thanks Eddie, had a gearhead friend up for the weekend, he was with me when it gave way and helped me get it fixed.
Thanks Dad, always good to hear from you!

By the way, is there any consensus on gasket quality? Is one brand really better than another? What is your experience?

[Mark Reynolds]

My theory is paper gaskets always leak. They also look ugly when the stick out past the casting.
For these reasons I use "The Right Stuff" and no gaskets.

[cv2065]

I've always used Felpro gaskets, but heard a lot of great things about The Right Stuff as well.

[CraigS]

I kept reading comments here over many years about the right stuff. So I tried it and it worked fine. About 3 months later I wanted to use it again but nothing would come out of the can. $15 for one use. I am not buying it again.

[FLPBFoot]

I was wondering if anyone would question that. The upper tube is from breeze but I am pretty sure the cap is the one that came from FFR. When I went to Auto Zone to replace it they said the cap should be 13 (for the Mustang 351W) so that is what I put back on it as a precaution, I can always change it back. However, should even 20 psi be enough to blow out a gasket that is properly torqued with adhesive sealer on it?

Just went and looked at my cap from FFR and it's a 20 psi as well. I'm thinking like you, going to get a 13. Keep the 20 in case.

[cv2065]

Anyone called Blueprint to get their take? My 427 comes in a couple of weeks and would be good to know. I’ll call and inquire if I get a chance.

[johnnybgoode]

This is not a car question but many of you have a similar engine so I am hoping someone may have an answer.

Blueprint 351W based 427. Cruising down the road when coolant starts gushing out. Pull over and coolant is flowing from the drain slot in the water pump mounting plate (the one that actually bolts to the block behind the water pump that the water pump is bolted to.) Tow it home, tear down water pump, and......... nothing! Everything looks fine! We had refilled the coolant (with water) when it was up on the jack stands and confirmed the location of the leak, the rear of the water pump. But when inspected it all looked normal. We had torn the gasket while removing the pump so could not ascertain its original condition. All we could guess was that the gasket had blown out (water flow was pretty substantial) and allowed water to leak into the back of the pump mounting plate and out the drain slot. This was only a theory but there was no other explanation. Cleaned everything up and put it back together. Everything is fine, not a drop of water leaking anywhere.

So, the question is, does anyone have any experience with a water pump gasket just blowing out for no reason? Why would this happen? How can I prevent it from happening again?

Engine did not overheat. Thermostat (180) seemed to be working as we had driven for about 45 minutes prior with no problem. Thermostat works fine now (after the fix). 20 psi pressure cap felt like it was working OK but replaced it just to be safe. I would rather not have this reoccur, but I have no clue why it happened!

If you are not familiar with the water pump I am talking about please do not ask me to explain the assembly. There is a backing plate with bolts that are inaccessible when the pump is mounted. If these are the cause of a leak the pump must be removed to tighten them. And if it leaks in certain positions on the pump, the fluid flows into a chamber behind the pump itself, which is what mine did. As far as I am concerned it is a goofy design, but it is what is on the engine (and thousands of others) so I have to deal with it.

Anyway, thanks for any advice you may be able to give.

I believe the torque spec for the WP bolts is 15-21 ft/lbs. You may want to re-check after a few heat cycles. I had a leak in mine as I forgot to tighten the two bottom thin head bolts. I took it apart and sealed the back plate to the pump with a new gasket and Right Stuff. Used some spare bolts to hold the pump and backing plate together for 24 hours then put sealant on both sides of the timing cover to water pump gasket and bolted it all up. Doing it in two steps made it much easier. Scott

[BB767]

I believe the torque spec for the WP bolts is 15-21 ft/lbs. You may want to re-check after a few heat cycles. I had a leak in mine as I forgot to tighten the two bottom thin head bolts. I took it apart and sealed the back plate to the pump with a new gasket and Right Stuff. Used some spare bolts to hold the pump and backing plate together for 24 hours then put sealant on both sides of the timing cover to water pump gasket and bolted it all up. Doing it in two steps made it much easier. Scott

Scott, you are correct on the torque, and it is VERY important on these bolts! The first two water pumps leaked from over torquing them! Blueprint did the first one, they told me what to use on the second one (35). Finally on the third pump we did 20 and, guess what, no leak! I used 20 again on this fix and no leaks first try also.

[AC Bill]

The only reason I can figure that FFR is sending builders 20 psi caps, is they are expecting you to use a T filler. The T filler, of which your overflow hose would normally be attached, would traditionally have a 16 psi cap, to function correctly. As you don't want any release on the radiator cap, you'd use a cap with a higher psi, such as the 20 you have received.

I know with my rad, accessing the cap to use it for filling, or top ups, would be very awkward, if not impossible. I plugged it and the overflow spigot, so it's as if the rad doesn't have a cap. Everything is done through the T filler, which also happens to be the highest point in the cooling system, and what you would want.

[CraigS]

I forgot to mention earlier that a couple of the h2o pump bolts need sealer on the threads.