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MGB New water pump leak

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Lynn Kirkpatrick

Lynn Kirkpatrick

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I have just finished replacing the water pump on my 68 MGB GT. Everything was all buttoned up, ran it up to temperature, topped off the radiator, checked all of the hose clamps, and was picking up my tools. I did one last check all around and underneath, and then I found the SPOT ON THE FLOOR. After further checking the drip is coming off of the bottom of the housing, at the bottom bolt.

I ran it several times, looking to see where it was really coming from. I don't think it is the weep hole, I rolled up a small piece of newspaper and stuck it in the hole. Nothing came out during a run. I also took out the bottom bolt and nothing came out during a run.

The gasket had a cut in it, but I used it (rookie mistake?) because I was using Permatex water pump RVT. I followed the instructions about apply, snug in place, wait 30 mins, torque, wait a day to fill.

If you've had this problem and fixed it, I'm all ears.
Thanks
 
The RTV ~should~ have sealed it. A "plan B" is to remove the pump with the gasket as intact as possible, go to the nearest NAPA store and get a sheet or roll of gasket paper the approximate thickness of the old one. Trace around the old gasket on the paper and cut it out with scissors. The holes are about the same diameter as those made with an oldie-timey paper punch.
 
And, please don't assume that because the pump is new that it is fine. Usually it is, but these parts are constantly being remanufactured by jobbers and the quality is suffering. Water out the weep hole is a sign of a pump not working.
 
As above, there are great pumps and crap ones. Easy trick for the holes on the gasket...cut out inner round hole, place material over pump housing, take a ballpeen hammer and using the round end tap on the gasket around the hole. The material will be cut around the hole. Repeat the procedure on all holes...be sure the gasket stays in place by placing a loose bolt in the holes as they are punched.
good luck!
 
:agree:

D is givin' away tricks o' th' trade. I jus' figger'd it'd be simpler to find and use a paper punch. The whole gasket can be cut with the ball-peen hammer method in most cases. It just takes a bit o' patience and careful placement. :wink:
 
Sorry! Learned it many years ago from an ex BL tech.
Yes, take your time, but is the best method I have ever found.
happy Christmas, Dr.!
 
Thanks for the tips on gasket making. Years ago my dad taught me the ball peen method. The hard parts are keeping the gasket from moving as you're tapping around the edge (spring clamps hold it as long as they don't indent the gasket) and tapping the holes that are real close to a boss or the impeller (in which case a real sharp exacto knife works).

I think I found the cause of the leak. The 1st pump that I got was the short nose because this is an 18V engine. Then I found the pulley for an 18G hits the short pump housing. I bought the right long nose pump to fit the pulley & fan. I had bought bolts for the short nose because the mounting bosses are different. When I put the long nose on I had to scramble for longer bolts on 2 holes. They ended up being a teensy bit too long. When I thought I was torguing the pump against the block, those 2 long bolts were bottoming out and not clamping. I should have looked closer, I may have seen the lockwashers weren't bottomed. When I pulled the pump out this am I saw the threads on the ends of the bolts were damaged. I used shorter bolts, made a new gasket and the pump is back in. Tomorrow I'll see if I did good. Fingers crossed.
Thanks
 
DZ said:
Sorry! Learned it many years ago from an ex BL tech.
Yes, take your time, but is the best method I have ever found.
happy Christmas, Dr.!
Click to expand...

My dad's dad taught me the same. And a happy Christmas back at ya!
 
Good catch, Lynn. And my Dad taught me that trick, too. Took a '30 Chevy 6 apart when we were 12, and made the gaskets with a ball-peen hammer.
 
Well, I have found the real source of the leak. It is the weep hole on the pump. Today I put in the coolant and started it. After it warmed up with the radiator cap on I started see drips on the bottom edge of the pump flange, but I could not see where they were from. I rolled up a small piece of newspaper and stuck it in the weep hole (not while the engine was running). This paper roll was long enough so that instead of the coolant running down the glossy painted flange, it collected at the end of the roll and then dripped. Pics are attached, I hope.

The good news is that I'm getting faster at changing water pumps.
 

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Its recommended to run a new pump with an air wrench on the bench before its installed , for a minute or so , just to heat the seal up and bed it in so it won't leak. However , my TCs water pump still leaked coolant when installed! So instead of R&R ing the pump ( PIA) , I replaced the coolant with distilled water and it stopped leaking immediately ! After driving the car all summer ( 750 miles) , I then replaced the water with coolant and its leak free. Evidently an antifreeze mix is too slippery to seat the seal.
 
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