[george kujanski]

Aronhk: I agree that it would be a good idea to summarize the various points brought up in this thread and others in the heating/cooling forum over the last few years.

Perhaps I may do that.

A recent thread also describes another interesting point. Apparently some factory cars, especilly those with AC, also used a smaller diameter water pump pulley whic increases the fan and pump speed. Several members have changed their pulleys and achieved a reduction in engine temps.

Your idea of adjusting the impellar position has merit, and probably the OEM pumps were set up correctly. My opinion is the rebuilders may not have been aware of what the proper dimensions should be so we end up with the variations that we see today.

When I first investigated mine, a hammer seemed to be the easiest way to experiment with since I don't have a press.

George

[aronhk_md]

A hammer is definitely my favorite tool.......lol. As with many aftermarket mass produced part I think the manufacturer in china maybe looks at an original......or even looks at someone elses copy of an original........then reaches into his bin and says, "This'll work...."

And over the years they get farther and farther from the original design. Since they are in China or Korea or wherever this stuff is sold in mass quantities with other model #'s, so even if handfuls are returned, it never gets up the line that something is wrong.

In this case it never gets up the line because we run the cars for years wondering whats wrong and why we are overheating.......never suspecting the new water pump.

I dont blame most for just taking the hammer and adjusting the plate a bit. Some seem so far out though they almost cant bend the plate in enough. I think like most things this should be a point at which one must say, STOP......I WANT TO GET THIS THING ON THE ROAD TODAY, BUT I WOULDNT HALFASS ASSEMBLE MY CRANK/MAIN ASSEMBLY OR MY RING END GAP OR MY ROD BEARINGS....

Most machine shops probably wouldnt charge more than a few dollars to press or pull your impeller to where it needs to be.



As for the smaller water pump pulley.....I found someone who has one and expect to be buying it next week. I dont have a need for one at the moment, so I'd like to start lending it out to people here for now so they can try it on their motors and SEE if it makes a difference. If it does they can search for one of their own and either mail it back to me or to the next person waiting.

Still I feel that most people are missing the real reasons they are overheating, thats why I thought about the checklist here as a sticky in the cooling section. So easy to forget things.........beating ones head against the wall checking timing, radiator, carb, pump, etc......................only to find out god knows how far down the line it was the heater core because I didnt even THINK of it.

Oh, and thanks again for starting it all!

[lkt1954]

Read this thread several times and it is great. Took the water pump off my 66 GTO today and the gap between the impeller and divider plate is at least 1/4" (no wonder it ran hot). Also the divider plate & internal housing is very pitted up. In fact where the internal housing nipple goes into the block the guy who rebuilt the motor put silicone on it to get it to seal-- is this right????

Tomorrow I plan on ordering a new cast wp from PY along with divider plate/internal housing and putting the GOAT back together and hope the heating issue goes away. A new plate tweaked to about .100 from the vanes should work.

In closing should the nipple on the internal housing be siliconed in place?

Thanks
Larry

[Aus Goat]

Thanks for this post !!!!
its saved me .
I thought i had a cracked Head and was pulling my hair out and i dont have too much left to pull out.

Thanks again

[lkt1954]

Well I am happier than a pig in mud on a hot summer day!!! Just finished putting a cast impeller water pump and new divider plates on my 66 GTO. The plate was massaged to where it was .10 from the impellers. Started and ran the car for 30 minutes and the temperature got to 190/thermostat opened and it dropped to 180 and stayed there. This never happened before 10 minutes and it was at 210--what a change.

Thanks to all for this great thread.

Thanks again
Larry

[Slick]

After modifying the separator plate as directed, I tried three pulley combinations.
1) 6.75" upper pulley, 8" lower. Result, cool as can be, never over 160*, fan noise and drag horrendous. 18.5% OD

2) 7.25" lower pulley, 8" upper pulley. Result, motor warms up to ~190* at idle, low speed, but cools to about 160-170 at 50MPH Fan very quiet. Pre-ignition when at full throttle. 10.3% underdrive

3) 7.25" pulley lower, 6.75" upper. Result, a little fan noise (more than I'd like), but stays at 160* all the time. No pre-ignition. 7.4% OD

It all makes a difference.

1971 GTO
462, 7K3 heads
Summit 2802 cam
iron intake, 800 Q-Jet
headers, stock exhaust
T400/10" converter
3.90 rear
3750 w/o driver
19" factory seven blade flex fan, Olds shroud 4-row factory radiator
No air

[Mr_GTO]

Going through my parts this weekend I found two original cast impeller pumps...one was from a '77 and the other a '71 I think. Going to bring them to Corvettes Carlisle and have them both rebuilt.

[MandevilleBird]

Which would you use? Flowkooler on left. Modine on right. 8 Veins vs. 6 veins...

[GT182]

Well, it's my turn in the barrel. Pulled my waterpump yesterday and the plates aren't good. Tho no holes I can see they are rusted in the places that aren't good. Plus the gap is not what it should be. So I ordered 2 new stainless steel plates from PY yesteday and hopefully they'll be here in a say or so.

I've got the 6 blade Modine pump like MandevilleBird has. At least it's still good and there's no leaks from it.

It's been suggested that I go to a 160 high flow t-stat so I'll give that a try too. Recored radiator and the new hoses have no problems, so it's getting this pump sorted out that should solve the overheating that popped a couple of weeks ago.

[Old Goat 67]

Gary,

When the new plates get there, check them for clearance very carefully with a new gasket in place. Post up a good clear pic when you do.

When I did it, I found no clearance at first and needed to press the impeller onto the shaft more, so I did not need to tweak the plates at all. Sometimes the pump is assembled with the impeller in the wrong location on the shaft for optimum water flow.

Charles

[GT182]

Sorry but no picture. Got the mew SS divider plates in this afternoon and everthing back together. My old plates had at least a 1/2" gap between the rear plate and the impeller. For the life of me I can't understand why, after the recore up to the outing to Pete's picnic it didn't over heat... even on the hottest days last summer. Check the new reap plate and it too was 1/2" off. Got it tweeked to 1/16", or very close, and all installed again. Longest part of the process is the "tweeking". LOL Disassembly and reassembly only took an hour each. And that's with pulling the radiator.

I even did some repainting of the engine yesterday and this morning before the parts came. Too dark right now for a photo but I'll post one tomorrow. I FEEL GOOD! I did it all on my own. Hey, this is my first time in all these years I've had to redo a Pontiac water pump. And that's for 2 66 GTOs, a 63 Grand Prix, a 66 Tempest, and a 79 Formula FB. Not bad for an amateur. LOL

[GT182]

After taking it all apart again, I got the heli coil in and all back together again. I stripped out the hole that goes in the timing cover where the lower hose hooks up. Now it's all tight and no leaks. Even looks to be cooling as it should again. Won't be out with it until tomorrow for our Fox Run Cruise Night. That will be the test to see if I screwed up or not.

[MandevilleBird]

Installed the new aluminum rad...runs 10 to 15 degrees HOTTER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!

[gtoformula]

Did you change anything else or are the hotter temps a direct old radiator/new radiator comparison? My aluminum radiator was a bit less wide than the factory copper radiator. I took a trouble light around the radiator on the engine size and watched for light on the bumper side. There was from a 1/2" to as much as 1" gap between the radiator and the core support. The thickest foam (with adhesive on one side) I could find was at my local Lowe's. I ran that down both sides and the bottom of the core support around the radiator and that sealed up just about everything. Now I can put my hand in front of the grills while the car is idling and feel the air flow moving strongly. If you have a gap around your radiator the air will take the least path of resistance ... just like fluids or electricity. Doesn't cost much or take much time to do this. It might help ... hope it does if you try.

[MandevilleBird]

No change other than the rad itself. I thought the new rad would be the trick. There are gaps as you described...not sure if there were with the old rad. FRUSTRATED!!!

[MandevilleBird]

I now have a waterpump pulley from a later model Pontiac. Its about 5-1/2" in diameter, as opposed to my stock 8" pulley. Problem: Its 7/8" deeper. Does anyone make a spacer to adapt this pulley to an 8 bolt set up?

[MandevilleBird]

Made a spacer. Lines up perfectly:

[GT182]

MB, after going thru all that, why didn't you install a fan clutch? You sure would have been better off with one instead of the spacer.

[MandevilleBird]

The spaceer I cut to 7/8" is between the pump and the pulley. I posted the photo to show alignment. ... I also have a clutch and fan. As long as the current set up with flexfan works, I'm leaving it alone. Previously it ran a bit hotter with the clutch and fan.

[GtoSS]

I AM NOW A BELIEVER,
I have a recently restored 1968 GTO convertible. Ever since the rebuilt 400 fired to life it ran HOT! Would creep to 220 degrees or more at idle and about 210 while driving. I had all the right parts, new 4 core rad, new fan cluth, shroud, new t-stat, reman water pump, etc. Is a fairly mild 9 to 1 400. I read this thread about a year ago and never gave it anymore thought. This past week I made decision that something had to be done as that is way to hot for my taste. I pulled the 8 bolt pump and I was thinking the best as it had cast impeller with the taller vanes. Checked clearance with divider plate and was 3/16 of an inch!! I then used hammer, dolly and anvil to tweak the clearance to .06". This afternoon I bolted it all up and put in coolant. I then started the car and was in dis-belief. I did not think it was going to get warm enough to open the 160 degree t-stat so i could entirely fill the cooling system. T-stat did finally open and I added more coolant and then put rad cap on. The car now runs at 175 degrees at idle, no matter how long it runs. I took out on the road and gets close to 190 degrees with a heavy load but then comes back to 175-180 when cruising at 3000 rpm's. THANK YOU all for the great information!!