The Stovebolt Site Forums The Shop Area Engine Shop Water pump, overheating questions

Finally getting the '51 back on the road after king pin job, and everything was going fine until I took it for a test drive around the neighborhood. Noticed the thermostat temp rising, and was waiting for it to fall when it hit 180*, but it didn't drop. I got back to the house as it was creeping toward 220*, shut it down and let it cool. I have an extra thermostat and a new water pump that I bought years ago due to the pump that came on the truck looks like it's the oldest part on the engine. Anyway, I pulled the thermostat, and it was pretty gummed up looking with rusty looking sediment. (The truck has been nearly undriven since the timing gear stripped a few summers ago. Had it replaced last summer, but didn't want to drive it until I changed out the king pins and put some new tires on it, which I've recently done.) I installed the new thermostat, took it for a 4-5 mile ride to the gas station to fill it up with fresh fuel (after pouring some octane booster in it), keeping an eye on the thermostat. When it hit 180, I was watching for it do open up and drop. It must have opened, because it never got above 180, and to get to the gas station I have to get out on the state highway for about 2 miles. I drove it back home and all was well, so I decided it would be a good time to flush the radiator and engine and put in new antifreeze. After draining it, I flushed it with the hose for about 5 minutes while it ran, then closed the petcock and filled it back up (while running, of course). I poured some cascade dishwashing powder in with it to break up any junk or rust, which i learned about on this forum. I then took it for another ride around the neighborhood and as I went down the hill and it warmed up, I started noticing that the gauge was rising and passing 180 again! I drove back up the hill to the house as it was getting close to the 220 high point. Pulled into the house just as it was starting to whine a little. Shut it down and checked under the hood. There was no water coming from the overflow tube. Nothing was leaking anywhere, including the water pump. I didn't mention, but the radiator is a "new" aluminum Champion that the PO put in before I got it 8 or so years ago.

So, I'm getting ready to go out and first open up and check the new thermostat, drain the radiator and see what's up there(still getting rusty looking water out of it after the first few flushes, hence the cascade in the last refill, before flushing it out again), then probably just go ahead and install the new water pump to be safe.

Has anyone ever installed a new thermo then had it not open after flushing it like that? Also, every water pump that's ever gone bad on me has had the tell tale weep hole leak at the bottom, but this one doesn't seem to be leaking. I will say that I had a good shop do the timing gear change, and I don't know if they pulled the water pump to get that job done, but I don't think so. Anyway, I'm on my way back out to start pulling and checking and replacing, so I wanted to ask you all what your thoughts are on this problem. The way I see it is, maybe the thermostat got clogged with something that broke loose, or maybe the pump was out/going out all along. But this wouldn't make any sense, since I drove it about 6-7 miles to the gas station after the thermo change witout it getting too hot before I flushed it out again. Thanks for any ideas or comments. Lee

Sounds like you ran into a similar problem that I have
You have a small airlock under the thermostat which doesn’t let it warm up as nice
Eventually it will get hot and open
But it’s much nicer for everything if you drill a small bypass hole through the new thermostat before installing
Then all these issues go away
-s

Ahhh. I wonder why the last one I put in didn't do this? Got em' both from classic parts. But I'll do that. I've got the thermostat pulled out, brought it in and checked it in a pan of water on the stove with the help of my wife's candy making thermometer. It opened up right before 180*. Now I've got the radiator out to pull the old pump and put in the new one. If I'd have gotten back on here earlier, I would have just tried drilling the hole and saved the water pump. But I've already got two bolts out and the radiator, and horn out of the way. I'm not going to put it all back together now, especially since I know the thermostat is good. But thanks for that info. I know I've heard a lot of talk about that bypass hole before. Didn't even think of it till you said it. Now I've got to post again to ask about the fan bolts. They're not left-handed threads, are they? I'm having a hell of a time getting one loose, so I came back in to check with 'the guys' to make sure I don't ruin them by forcing them the wrong way. Be back in a bit to see if anybody knows.

On my stock trucks 50-53 I don’t recall any left hand bolts anywhere on the vehicle
I’ve had fans on and off and those for sure are normal thread on my trucks.
-s

Alright, then, I posted in general truck about those bolts, and before I came back in, I got the pump bolts out with an open end wrench, then put the pump on my vise and pounded my wrench a few times and it broke loose. It was TIGHT! But not as tight as my heater hose inlet. But it came out too. Is h-e-c-k a cuss word? I had h-e-l-l censored not long ago, and I asked the moderator, what if I talk about heaven and hell? the asterisk police got that too. Funny.

Stovebolt software automatically removes objectionable words. Moderators have nothing to do with that process. Doing as you have done in the above post, ie; putting dashes between letters fools the software but is still objectionable to members. Please do not do it in future posts. Stovebolt.com is considered a family friendly website and we want to keep it that way. Thank you.

Ok, now I've gotten the pump back in and the heater hose and generator bracket on and torqued. Ready to put the pulley and fan on before installing the radiator, but I've got a problem. Maybe it's suppose to be this way, but I'm not sure. The pump I bought from Classic Parts years ago, specifically for newer engines put into older 3100's, has a shorter shaft on it, which is fine with me, although it will bring the fan away from the radiator. Problem is that in order to get the fan to not hit the harmonic balancer on the crank shaft (it sticks out around the pulley and comes another 1/2" or so forward of it). I can solve this problem with the steel spacer they sent with the pump, but it ends up leaving the shaft about a sixteenth inch short of even being flush with the fan's center hole, much less making contact by passing through the fan to keep it centered. I understand the 4 bolts will hold it in place, but it seems to me that when something is riding a shaft, the shaft should be through the fan metal for centering. Here are a few pics. The old pump is spinning freely without any bearing issues. I'm wondering if I should just get another gasket and put the old one back on, or chance this short shafted new one. Why does the new one have a short shaft? With a spacer that doesn't allow the shaft to protrude through the fan, it seems like somebody messed up here. Or is this not the pump I need?

Will do. I'm a family friendly guy. Although I don't believe h-e-c-k is crude or non-family friendly. And I'm a Christian, so hell is a much talked about place in my circles. But I do understand that there are people who abuse it's use, so I'm not opposed to being edited for that. But I'll do my best to go by the rules. Being around Ironworkers daily for 30 years will put some rough edges on ya!

Unless somebody has repositioned the radiator to the front of the mounting cradle, a long shaft pump generally puts the fan into the radiator. Any late model water pump can become a "short shaft" by pressing the fan hub back and cutting the shaft to the proper length. If a long shaft pump fits your 51 truck, somebody must have moved the radiator forward. A simpler fix that keeps the fan in the right position vertically is Dave's adapter plate that allows a 216-style pump to be used on the 55-up engines.
Jerry

I've got a '56 235 engine with a GM water pump that needs rebuilt. It's running ok, but it's not spinning as easy as I'd like. I just pulled it off to put on a new one I bought from CP a few years ago, but it's not going to work out. This is the pump model that they use when putting a later model 235 in an earlier truck (mine's a '51 3100). If there's anyone who knows a good rebuilder for these, let me know. Really disappointed the CP doesn't work, even though they say it's made for just this application. The shaft is too short to make contact with the fan blade's center hole when the included spacer is used. The spacer has to be used so the fan will clear the balancer, but the new shaft is not long enough for the pulley, spacer and fan to all ride on it. It's about an eighth inch short of being full bearing on the spacer, also. Bummer. And since I bought it years ago, I don't think they'll take it back. So, if there's anyone who does this kind of work, let me know, please. Thanks

By 'forward', do you mean toward the front of the truck or toward the engine? Actually, it has been jumped from inside the radiator bracket and is now bolted onto the engine side face of that u-channel bracket. It's been that way since I bought it. They put a new Champion aluminum radiator and installed the 235 with the pump that's on it, too. The old pump's shaft is 1 1/2" longer than the new one, but the old pump's pulley is 3 1/2" deep. The new pulley is 2" deep. That would come out even, but the 3/8" spacer, although it puts the pulley in the right place, ends up leaving the shaft 3/32" below the face of the spacer (not flush with its outside face). Then there's the 3/16" thick fan blade that has no bearing at all on the shaft. This, plus the slop in the notch spaces in the spacer for thru-bolting makes it even worse. The new classic parts pump's shaft is too short. The old one fits and works just fine. I just think somebody errored in not taking into account for the crank shaft ahead of the lower pulley, misjudged the thickness of the 3/8" spacer, or the easy answer would have been make the shaft a quarter inch longer so the fan could spin on the shaft, not just the spacer with over sized slots. Is Dave's spacer plate 3/8" deep? If so, it won't work here.
I actually just got n the general questons forum and asked if anybody knew a good pump rebuilder. The old one is OEM GM. The CP part, who knows? If it's a refurbished original, they goofed on the shaft length.

How about machining an extension for the short pump shaft and bolting it on? Drill and tap the shaft for a 1/4-28 thread Allen bolt and attach a 1/2" or 5/8" long extension onto the pump shaft. Any machinist worthy of the name can do that- - - -he doesn't have to be a "water pump rebuilder". Send me the short shaft pump and I can do it.

Dave's spacer is a 1/8" thick plate that replaces the back plate of a 216 pump. It covers the hole in the front of the block for the 55-62 low mount water pump and positions the pump correctly vertically in relation to the radiator in the 54 and earlier trucks. 55 2nd. series and newer engines put the water pump too low on the radiator for the fan to cool efficiently.
Jerry

Well, Dave's plate, if I'm hearing right, would raise the pump and shaft up, then? That would probably allow the fan blades to be above the top of the harmonic balancer, although I didn't measure to see how far up it needs to come. With the pulley on but the spacer left off, the fan and pulley fit like they should. But the blades hit the balancer on their back edges when they're turned. Got a link to his plates?

I'm still going to have the old one rebuilt somewhere. But, the idea of having a high rpm fan depending on a 1/4" bolt instead of the full strength of a solid bar of stainless steel doesn't sound like a good idea. No offense, but I'll pass on that. Not to mention having a bolt sticking out of the fan shaft blade. How could that be trued?

I give up- - - -I've offered to help, and you're making excuses. The bolt wouldhold AN EXTENSION TO THE SNOUT OF THE SHAFT TO CENTER THE FAN. The four bolts would still hold the fan onto the hub. Good luck with whatever you choose to do!

Contact Stovebolkt member Pre-68 Dave for a link to the adapter that he's been selling for years. It works.
Jerry

Sounds like your radiator was repositioned forward to accommodate the longer shafted water pump that came on the ‘56 235. My ‘59 235 was that way in my ‘52 3100 when I first purchased it.

If this is the case, you options would be:

• (1) Use the CP pump and reposition the radiator back to the original position. Pros it works and many have gone this route. Cons, it positions the water pump too low for maximum efficient cooling.
• (2) Buy a water pump repositioning adaptor plate (available thru a fellow ‘bolter, Pre ‘68 Dave), and buy a new pump for a '51 216/235. Then, reposition the radiator in its original installed position. Pros, it positions the pump in the original position for efficent cooling. Cons, it's more work and more money.
• (3) leave the radiator in it's installed position and buy a new pump for a '56 235 (original style with the longer shaft) . Pros, much less work and money. Cons, it still maintains the lower pump position lowering fan cooling efficiency.

I opted to buy the adaptor plate and new original pump, to retain as much originally and cooling efficiency as I could.

I posted two pictures of my radiator position, a before and after so you could see what I am talking about.

Check these guys out. They rebuild Alternators, generators, starters and I am pretty sure water pumps. They rebuild and ship all over the U.S. Last time I was there getting an alternator to replace my generator they told me they rebuild and ship about 40-60 alternators a week. Very helpful group of guys. they have been in business a long time.

https://www.hamiltonsalternatorsandstarters.com/

You can buy Pre ‘68 Dave’s adaptor plate by sending him a PM. Here’s his profile [LINK].

Phil- thanks for the pics and advice. Actually, my radiator has already been moved back to the rear of the bracket, and has used this long shafted pump ever since I bought it. I bought the cp pump due to it's description on classic parts of fitting later (55 on) 235's in older trucks. The problem isn't the space between the fan and radiator, though. The problem is without the added spacer (3/8") the fan won't clear the harmonic balancer below it, but with the added spacer, the shaft is about 1/4" too short. It isn't long enough to make it all the way through the spacer, thus the fan's center hole is not making contact with the shaft at all. Also, with the spacer removed, the blade and the pulley are in their correct positions on the shaft, but the fan hits the balancer. So it looks to me like CP added a spacer to correct the fan hitting the balancer, but didn't think to add the extra length to the shaft to accommodate it. Sort of a lazy fix, or a mistake on shaft design. I'll post some pics of what I'm talking about when I get out there this morning and work on it some more. But since it's present set up has worked for this long (almost 10 years since I acquired it), I'd rather just keep the pump I"ve got and eat the cp pump. I'll call them up and see if they'll take it back, but classic parts has always had a reputation of debating customers on problems with the "we're right, you're wrong" mentality, so that probably won't get any results. But thanks.

Dave- thanks for the recommendation. I'll check them out.

For right now, I'm just going to go get new thermostat and pump gaskets and put it back together. When I find a pump rebuilder, I'll pull it off and have it redone. Just really disappointed in cp's supposed 'this will fit what you need' ad, which is a mistake. Thanks guys.

There is another possibility. Many of the later 235’s installed into the AD trucks ran into the issue of the water pump being to long. Some just moved the radiator forward, like in my case but others calculated the interference, and pressed the fan hub further onto the pump shaft, then cut off the excess. Since your radiator is in the original position, this may be your case.

actually it's not in the original position. It's on the engine side of the radiator frame, like Phak1's second pic above. The pump has a long shaft, but it has worked well for years this way.

I have merged the GTT thread with this one since the same things are being discussed in both threads.

The rear of the radiator support is how the factory mounted the radiator, like in my second picture. This would normally place the fan blades of a late model 235 into the radiator (as Hot Rod Lincoln has previously pointed out). There is something missing from this equation that we are not seeing.

If the new pump fits the engine block, that confirms it a late model 235. I have the water pump I replaced from my ‘59 235 and when I get home, I will measure the distance from the pump casing to the end of the pump shaft to see if the fan hub has been pressed back.

I think the confusion must be that the aluminum radiator must have a much greater offset than original, to allow for the long shaft pump.

I was thinking the same thing, Dave. Haven't measured the depth of it yet, and I don't know what the depth of the original was. I'll take some measurements and put the old one back on and set the radiator back in to give a better idea of what I've had going on these past 7 1/2 years since I bought it. I got my stack of receipts out and found that I'd bought the new pump in 2019, and it's listed on classic parts as a 'short shaft', and that it's made specifically for this purpose. Just can't understand why they would build one with a shaft not long enough to use the spacer they provide. Like I said, if it weren't for the harmonic balancer just below it, it would work great without the spacer. But the spacer requires more length to the shaft, which didn't get included. Unless the one I have didn't use the right shaft.

Is the entire fan blade pointed/aimed/orientated into the cooling ribs/mesh-area on the radiator?

Just measured a stock pump for a ‘59 235, which should match yours.
They are as follows:

• From the casing to the shaft end: 2-9/32"
• From the pump casing to the fave of the fan hub: 1-31/32”
• From the end of shaft to the fan hub face (where the fan sits): 1/4"

Just got back on here, and I think I may know what's going on. 1st of all, after I got my new thermo and pump gaskets, I decided that the old pump was spinning ok, the new pump wasn't going to get it, and the thermostat tested good and I drilled a 1/16" hole in it just in case, so I put it all back together so I could at least get it back in the drive way and off the curb where I was draining it. The radiator seems to drain just fine, so after filling it up, I started it and let it run for about 5 or 10 minutes to see if all was well. The belt is good and tight, the pump was spinning with no leaks. It wasn't warming up real quick, so I closed the hood to take it for a ride around the block to watch the thermostat open up, but when I got in the cab, it was over 180 again, and slowly creeping up. I shut it off, let it cool, then took it around the block, and it was getting hot again, so I parked it in the driveway to think on it for awhile.
Went back to the shop manual and re-read the troubleshoot on the cooling system, and there it was. Last thing on the list is to check the manifold heat valve in case it's stuck. Dug a little more and found out what happens when it gets stuck in the carb heating position, and thought that might be it. I went out and checked the heat riser spring and shaft, and nothings moving. I would say it's definitely stuck. Sprayed some PB Blaster on both ends at the manifold, but so far no movement. Kind of late today, so I'll get out there and pull the carb tomorrow and see if I can get it to move. Anybody done this before? Per some questions on replies above, I took some pics of the way the fan has always been positioned since I got it. It's always worked fine this way, but I guess it could be better. The radiator is actually in the frame, not on the front of it like I was thinking. (the wings that bolt onto the radiator frame are attached to the engine side of the outer U leg, not the engine side of the inner channel leg. my mistake) And it is setting low on the radiator, but it's not below it. But like I said, it's always run fine except for replacing the thermostat once.

Why would you want to pull the carburetor? The heat riser is in the exhaust manifold.