Water pump failures
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Water pump failures
Why are my water pumps failing? I've had the car a year now and I need another water pump. This will be the fourth one. The first one failed after I'd owned the car for a month or two, and I thought nothing of it. I replaced it with a water pump from Pep Boys. It was a Bosch unit and it lasted about a week. I think it was junk from the get go. I returned it and got one from NAPA. That one failed today. (bearing sqauealing, or impeller rubbing the back side of pump, but still works)
The engine is a 327 350hp from a '67 corvette. It does not have the correct intake manifold. I am mentioning this because I read something in the archives after doing a search that the high hp cars had a bypass to prevent cavitation? The engine has extra pulleys so I installed a belt from crank to water pump in addition to the alternator belt. I do not believe the belts are too tight
The first and third water pumps failed immediatly after a couple of spirited runs through the gears near redline.
So what do you think, am I just unlucky with water pumps?
Thanks
Gerry
The engine is a 327 350hp from a '67 corvette. It does not have the correct intake manifold. I am mentioning this because I read something in the archives after doing a search that the high hp cars had a bypass to prevent cavitation? The engine has extra pulleys so I installed a belt from crank to water pump in addition to the alternator belt. I do not believe the belts are too tight
The first and third water pumps failed immediatly after a couple of spirited runs through the gears near redline.
So what do you think, am I just unlucky with water pumps?
Thanks
Gerry
Le Mans Master
Joined: Jan 2002
Posts: 8,913
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The by-pass hose is not an issue. The heater acts as a by-pass circuit as well. Unless you have some sort of shut off. In that case, there is a small hole in the left boss for the circulation.
When running can you notice any wobble from the pulley?
Mark
When running can you notice any wobble from the pulley?
Mark
Le Mans Master
Joined: Apr 2006
Posts: 7,033
Likes: 603
From: Limerick Pa
Are the pulleys lined up? If they are cocked they will make the bearing in the pump go bad, but probably not in a day. It might if you gorilla tightened the belts and they are not aligned correct.
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
I didn't notice any wobble. I'll check that again with the new pump.
Gerry
Melting Slicks
Joined: Jan 2003
Posts: 2,817
Likes: 21
From: Somerset, NJ
Doesn't surprise me any since most of the new replacement water pumps out there today are coming out of China whether it be sold by NAPA or anyone else. Funny though back in the early 70's I remember well before getting into the auto parts business replacing 3 Borg/Warner brand new water pumps in a row in my '67 Vert. The 3rd one held out but the first 2 leaked from the weep hole right from the get go and back then they were made in the USA.
Le Mans Master
Joined: Apr 2000
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From: New York New York
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I had a customer last week with a 79 Vette who replaced a couple of pumps before coming to me.
After questioning him I found he had an aftermarket fan clutch on the engine.
When I asked if he checked to see if the bushing was in place he said there was no bushing in the fan clutch.
Most after market fan clutches come with a bushing to reduce the pilot hole to 5/8 instead of the later 3/4". Early small blocks have the smaller pilot shaft.
Just something else to look for.
After questioning him I found he had an aftermarket fan clutch on the engine.
When I asked if he checked to see if the bushing was in place he said there was no bushing in the fan clutch.
Most after market fan clutches come with a bushing to reduce the pilot hole to 5/8 instead of the later 3/4". Early small blocks have the smaller pilot shaft.
Just something else to look for.
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Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
When I asked if he checked to see if the bushing was in place he said there was no bushing in the fan clutch.
Most after market fan clutches come with a bushing to reduce the pilot hole to 5/8 instead of the later 3/4". Early small blocks have the smaller pilot shaft.
Just something else to look for.
Most after market fan clutches come with a bushing to reduce the pilot hole to 5/8 instead of the later 3/4". Early small blocks have the smaller pilot shaft.
Just something else to look for.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
A clue would be that you get a good seat of the pants and hand massage from the engine vibrations coming through the steering column and the seat. If that's what's wrong, (and there is something wrong) I'm not suprised that you would have water pump problems. Ordinarily, even rebuilt pumps will last a long time if you don't overtighten the belts.
[QUOTE=JohnZ; that tiny off-center difference multiplied by the weight of the fan clutch will tear up the bearings and seals in a water pump almost immediately.[/QUOTE]
[QUOTE=JohnZ; that tiny off-center difference multiplied by the weight of the fan clutch will tear up the bearings and seals in a water pump almost immediately.
[/QUOTE]
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
A clue would be that you get a good seat of the pants and hand massage from the engine vibrations coming through the steering column and the seat. If that's what's wrong, (and there is something wrong) I'm not suprised that you would have water pump problems. Ordinarily, even rebuilt pumps will last a long time if you don't overtighten the belts.
A hand massage to the seat of my pants!?
No, the fan clutch is a replacement that came with a bushing to center it. I will double check when I re-assemble.
Thanks,
Gerry
Melting Slicks
Joined: Nov 2002
Posts: 2,460
Likes: 5
From: Wheaton IL
I had the same problem. Went through two Carquest pumps that were blown out by runs to 6500 RPM. I had Arthur Gould build me one with a "heavy duty" (as he called it) bearing and I haven't had a problem since. Arthur advertises in NCRS and is a super nice, honest, and reputable guy. He specializes in Corvette water pumps.
I should have known I was installing junk from Carquest when the computer said it could also be used for truck applications.......
Your belt tension could also be too tight.
Brian
I should have known I was installing junk from Carquest when the computer said it could also be used for truck applications.......
Your belt tension could also be too tight.
Brian
Safety Car
Joined: Nov 2001
Posts: 4,424
Likes: 619
From: northern CA
Weiand carries the 'Action-Plus' line of water pumps. The one I bought was aluminum and has a 3/4 inch impeller shaft. Nice beefy unit. .. The front of the impeller shaft is stepped down to a 5/8 inch pilot that will accept the earlier style fan clutch.
Race Director
Joined: Nov 2000
Posts: 10,340
Likes: 664
From: Beverly Hills (Pine Ridge) Florida
"Trial and error" is the belt size I found! Variations in crank and water pump pulley diameter will force you to try a variety of belts (unless someone has the exact same pulley combination, and can supply you with the belt they used).
Just take a rough measurement with an old cut belt (or even a tape measure), and ask an old school parts store to let you try belts around the size you measured. Putting the belt on is not difficult, once the fan and water pump pulley is removed. Just reinstall the water pump pulley with the new captured belt.
A caution to NOT tightening up the accessory belt too much. Remember that excessive belt tension, loads the crank snout upwards, and will damage both the crank snout journal and upper bearing half (besides trying to bend the crank). Ever remove the main bearings, and wonder why the upper front bearing half was worn? There is a limit as to too much tension.
Good luck,
Plasticman
Last edited by Plasticman; Jun 18, 2008 at 09:04 AM.
Le Mans Master
Joined: Nov 2000
Posts: 7,246
Likes: 21
From: Going too fast over the hill. Iowa
My 66 sb engine has an A-C compressor for the first 7-8 years I owned it, It cracked the pump housing any time I power shifted with A-C running or revved to the limit. After 7 or 8 failures, I finally installed a 71 GM pump, much heavier duty, but required a TransAm A-C/alternator pulley and 3/4 inch fan adapter. That worked for 7 years.
A few of years ago I got a Stewart cast iron pump which has all the reinforcement webs in the casting that the 71 GM pumps do - along with the bigger bearings for the 3/4 shaft (like the gm 71 pumps) BUT the nose of the shaft is 5/8inch, so the stock fans, pulleys, and clutches for a 63-67 will fit.
I am very happy with the Stewart pump, and I was able to reinstall the factory pulley.
A few of years ago I got a Stewart cast iron pump which has all the reinforcement webs in the casting that the 71 GM pumps do - along with the bigger bearings for the 3/4 shaft (like the gm 71 pumps) BUT the nose of the shaft is 5/8inch, so the stock fans, pulleys, and clutches for a 63-67 will fit.
I am very happy with the Stewart pump, and I was able to reinstall the factory pulley.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Many years ago (at 6500 + rpm) the front bearing seized and twisted off the shaft.
Fortunately it only took out the shroud and rad.
I had no success with any of the rebuilt pumps. A few trips to 6,500 rpm and the pumps
were toast.
I finally went with a Stewart Aluminum pump ( 3/4 inch impeller shaft/5/8 inch pilot) and
it has been working great for about 13 years now. (Not NCRS correct, however the fan
has not gone thru the rad lately).
Thanks, Barry
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
I think I found it
While putting the water pump on last night I paid close attention to the centering bushing in the fan clutch. I saw that it wasn't long enough to be flush with the mating surface on the pulley. It was recessed a good 1/4" or more. And it was a loose fit, it would drop out if you tipped it upside down. Then I looked at the water pump shaft. It only protruded past the pulley by about 1/8". So if I just threw the fan clutch on without paying attention, that bushing would be recessed too far back to come into play. I dropped a couple of flat washers behind the bushing to bring it flush, and I think I'm good to go!
I don't know if this was the problem with the other pumps because they are gone and I can't look at them, but it would have been a problem with this one if I hadn't paid attention.
So I would like to thank you guys for helping me out with this one.
Gerry
I don't know if this was the problem with the other pumps because they are gone and I can't look at them, but it would have been a problem with this one if I hadn't paid attention.
So I would like to thank you guys for helping me out with this one.
Gerry
Thread Starter
Drifting
Joined: Jun 2007
Posts: 1,552
Likes: 99
From: Lake Villa Illinois
St. Jude Donor '14
Mine is a NAPA Premium XL 25-7550
The engine is a '67 327-350Hp that had air and power steering
the water pump pulley has 2 grooves
Edit: Thats 25-7350. I was looking at the wrong belt
Crank has two grooves and a third pulley bolted to the front of that.
Hope that helps.
Gerry
Last edited by Mossy66; Jun 18, 2008 at 05:12 PM. Reason: Stupidity
Le Mans Master
Joined: Apr 2005
Posts: 6,354
Likes: 424
From: Seattle Area WA
I'd at least run a Delco water pump and new Delco fan clutch, 3916141. The aftermarket clutches do not seem to hold up that well, kind of get what you pay for with fan clutches.
Last edited by Scott Marzahl; Jun 18, 2008 at 05:27 PM.