Author Topic: Water pump replacement in '78 TA pontiac 400  (Read 970 times)

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Offline CRU

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Water pump replacement in '78 TA pontiac 400
« on: June 21, 2018, 11:28:33 AM »
Looking for any advice/tips on replacing a water pump on a '78 TA with a pontiac 400. 

I'm assuming my water pump went out since I hear a loud thumping noise under load and coolant was leaking bad from the weep hole of the water pump - guessing the bearing are bad?  Also, I'm told you should replace the fan clutch when replacing the water pump?  Got the fan/clutch off along with the alternator.  Should I remove the crank pulley - will that give me more room to put the new pump on?  Also, should I use silicon at all on the new gaskets?  What torque spec should I use on the pump bolts (15 lbs?) and what pattern should I tighten them in?  Anything else I should be concerned about?


Offline 78T/AKID

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Re: Water pump replacement in '78 TA pontiac 400
« Reply #1 on: June 21, 2018, 11:46:53 AM »
If that is the original water pump to the car depends on the date code i would be interested in buying your old water pump from you. Shot me a Pm with your info so I could contact you or help your with the build date o your car. Thanks Matt

Offline 78w72

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Re: Water pump replacement in '78 TA pontiac 400
« Reply #2 on: June 27, 2018, 10:30:15 AM »
a bad water pump should not make a loud thumping noise under load, that sounds like something else causing the noise.  but if the pump is leaking at the weep hole it needs replaced.

crank pulley doesnt need to come off for water pump change. also fan clutch doesnt need replaced just because water pump went bad, if the clutch is still working its fine to leave it alone.

i suggest getting a repair manual, it will tell you the torque specs etc.  i use a thin layer of sealer on both sides of both gaskets, ultra grey or ultra black permatex is good stuff, a thin bead spread out with your fingers then follow instructions on the tube for curing.  the bolts can be tightened in an even pattern, no specific sequence, i do the top bolt, then bottom, then left/right sides, then the rest criss crossed kind of like a lug nut pattern.  once its together & dried start up & check for leaks.  then after a few heat cycles snug the bolts again, you can get to most of them with a little creativity with the wrench.  also good idea to use anti sieze on the bolts going into the aluminum timing cover.  its a pretty basic job & easy to do if you follow the manual.

also, pontiac pumps need to be clearanced to the divider plate to cool properly. when assembled on the bench the impeller should be as close to the divider plate as possible, like .010 clearance.  if needed gently hammer or bend the divider in then test fit untill there is a tight clearance. if its too big of a gap it wont work right & you can have overheating issues.   
78 w72 ws6 4 speed
81 turbo pace car
lots of other past t/a's