Water Pump to Engine Block Gasket Failure- Why did this happen?

[Mark E.]

What did I do wrong, and how can I prevent this from happening again?

The gasket between the water pump and block on the passenger side blew out during my Sunday drive yesterday. The engine was running at about 180 degrees when it occurred. The good news is the engine was still at normal operating temperature when I shut down even though coolant was gushing out of the engine-to-water pump mating surface. I say the gasket "blew out" because I can see a portion of the gasket sticking out where the leak occurred. It wasn't like that before the leak; I believe the coolant pressure pushed the gasket out a bit.

I installed the water pump about 1,000 miles ago; no leaks until this failure (the engine is very clean and I diligently check for leaks after every drive). I used the gasket that came with the pump, along with I believe Permatex #2. I'm fairly confident the attaching bolts are tight.

I've installed a lot of water pumps over the years, but never had this happen. When I repair this mess, what gasket/sealant combination do you recommend?

Thanks,

[Joe L.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

What did I do wrong, and how can I prevent this from happening again?

The gasket between the water pump and block on the passenger side blew out during my Sunday drive yesterday. The engine was running at about 180 degrees when it occurred. The good news is the engine was still at normal operating temperature when I shut down even though coolant was gushing out of the engine-to-water pump mating surface. I say the gasket "blew out" because I can see a portion of the gasket sticking out where the leak occurred. It wasn't like that before the leak; I believe the coolant pressure pushed the gasket out a bit.

I installed the water pump about 1,000 miles ago; no leaks until this failure (the engine is very clean and I diligently check for leaks after every drive). I used the gasket that came with the pump, along with I believe Permatex #2. I'm fairly confident the attaching bolts are tight.

I've installed a lot of water pumps over the years, but never had this happen. When I repair this mess, what gasket/sealant combination do you recommend?

Thanks,

Mark------


The gaskets that I've seen supplied by commercial rebuilders with rebuilt waterpumps scare me a bit. I don't think I'd use them. Having one "blow out" as you've described does surprise me, though. I've never seen that happen. If it were me, I'd use a GM #3860039 or a Fel-Pro 30060. As far as a sealer goes, the Permatex #2 ought to work fine. However, if it were me, I'd opt for a VERY thin coating of Permatex Ultra Copper or Ultra Black.

[Edward J.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Mark, just use a fel pro gasket as Joe says, I personally use 3M weatherstrip adhesive it will basicly weld the gasket to pump and will stop blow out. and proper torque is important.

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Joe, Edward,

Thank you.

[Terry D.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Mark
Did you check the bolts after a good warm up run? The gasket blowout is caused by either the bolt came loose a little or the surfaces are not flat and smooth! Sometimes bolts will loosen up a bit after a good long run. Before I take my 62 on a trip I check all the bolts and nuts I can to make sure none have vibrated loose. Just my old 2 cents.
Terry

[Bruce B.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

FelPro gaskets with Permatex #2 on all surfaces.
As Terry said check for tightness on a regular basis.
Bruce B

[Loren L.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

What year car?

[Duke W.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

When everything is cleaned up lay the pump against the block with the bolts started, the push the pump against the block and use a .0015" or .002" feeler gage to check the gap. Check around the edges with the pump pressed against the block, then press the pump against the block with the gage inserted and see if it easily pulls out. It if does, either the block or pump mounting surfaces are not flat.

It's not uncommon for the pump mounting surfaces to be a bit warped after multiple rebuilds over the years.

I'm not sure how much is acceptable, but I'd say if it's more than .003" you should check both the block and pump with a machinists bar and dress down high spots with a file. Then using a high quality gasket/sealer as previously recommended should do the job.

Duke

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Mark
Did you check the bolts after a good warm up run? The gasket blowout is caused by either the bolt came loose a little or the surfaces are not flat and smooth! Sometimes bolts will loosen up a bit after a good long run. Before I take my 62 on a trip I check all the bolts and nuts I can to make sure none have vibrated loose. Just my old 2 cents.
Terry

That's a good practice. I did check those and other bolt torques ~100 miles after restoration. But not since then.

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

What year car?

Stock 1970 LS5.

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

When everything is cleaned up lay the pump against the block with the bolts started, the push the pump against the block and use a .0015" or .002" feeler gage to check the gap. Check around the edges with the pump pressed against the block, then press the pump against the block with the gage inserted and see if it easily pulls out. It if does, either the block or pump mounting surfaces are not flat.

It's not uncommon for the pump mounting surfaces to be a bit warped after multiple rebuilds over the years.

I'm not sure how much is acceptable, but I'd say if it's more than .003" you should check both the block and pump with a machinists bar and dress down high spots with a file. Then using a high quality gasket/sealer as previously recommended should do the job.

Duke

Thanks Duke. I'll definitely check this as you suggested.

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Just for grins, check the pressure cap for its release pressure?


As an aside I had this happen to my 85 when it was 2 years old. The pump to block gaskets were almost "pulverized". I don't recall that I came up with an explanation for the failure. I installed FLAPS gaskets with #2 Permatex, and now almost 30 years and 40K miles later, that repair is still holding. Sometimes $hit just happens.

I was also wondering about the pressure. I know pressure builds after shut down, but the velocity of the coolant stream gushing out of the pump/block mating surface was incredible. It just seemed like a lot more than 12-18 pounds.

But if the cap didn't release pressure as it should, I'm surprised the pump gasket was the weak link. I would expect a hose to blow off or maybe a seal failure.

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

I wanted to share the rest of this story.

As I removed the water pump to repair this problem, I noticed the two block-to-pump bolts on the right side were not torqued down. They were tightened just enough to contact the lock washers. So it seems this is the root cause of the gasket failure. I'm surprised the seal lasted as long as it did- about 1,000 miles.

I originally installed the water pump, so how did this happen? I believe I finger tightened the bolts then wrenched one more turn with the idea of letting the Permatex #2 set up before final torquing. Then I failed to return later for the final torque down.

Thank goodness I'm not a professional mechanic.

[Richard M.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Mark, One more thought, maybe someone mentioned,......

Make sure the bolts are not too long and bottoming out into the block. Those are blind holes and you may think they're tight, but not tight enough to hold the pump on as they may be bottomed out. Remove the bolts and check depth with a screwdriver or drift, then measure the bolt to tip below the lockwasher. This may be why they loosened.

Rich

[Mark E.]

Re: Water Pump to Engine Block Gasket Failure- Why did this happen?

Thanks Rich; will do.