Bad/Weak water pump?????

[Treblig]

I had posted a long time ago about my motor running hotter on the highway. RRR told me that my lower hose might be collapsing. I finally got around to changing the lower hose with one that has a spring inside. I took it out on the highway and nothing changed, it still runs around 200 degrees at 55 MPH. If I drive 70 it gets even hotter but in town (below 40 MPH) it stay around 180/185.
When I replaced the hose today I filled the radiator with water and anti-freeze and let it run with the cap off until I saw the water flowing inside the radiator. Well...it ran for a very long time and the temp went up to 180 and wouldn't go any higher. The cap was still off but I noticed that there was hardly any water moving looking through the open radiator cap hole. Every other car I've worked on usually has lots of water moving with the cap off. Anyway, after driving on the highway I came to the conclusion that the water pump must be weak or bad because it has very little flow and it doesn't get hot when sitting still.
My questions is.....When I looked up high flow water pumps for my '69 318 Barracuda they talk about AC or non AC, it there a difference.
I do have AC but what's the difference??? Any help with the low flow is appreciated!!


Thanks,

Treblig

 

[krazykuda]

I've heard of new pumps where the shaft was not staked properly to the impeller blades and would slip and not spin the impeller....

 

[TrailBeast]

The symptoms match a bad thermostat also.
They also tell me coolant flow is the problem, and it could very well be the water pump but I sure would swap that thermostat out for a tested working one first.
Standard water pumps have 7 impeller vanes and AC pumps have 8.
I opted for 8 since my car generally runs at lower RPM's I figured the extra vane would help the flow at lower speeds.

I also have seen those pumps where the impeller came loose from the pump shaft.
(They kind of still work, but act like you say yours is acting)

 

[Treblig]

I've heard of new pumps where the shaft was not staked properly to the impeller blades and would slip and not spin the impeller....

I bought the car over 3 years ago and it came with the pump already installed so I don't know the history. But what you're saying makes sense.

treblig

 

[Treblig]

The symptoms match a bad thermostat also.
They also tell me coolant flow is the problem, and it could very well be the water pump but I sure would swap that thermostat out for a tested working one first.
Standard water pumps have 7 impeller vanes and AC pumps have 8.
I opted for 8 since my car generally runs at lower RPM's I figured the extra vane would help the flow at lower speeds.

I also have seen those pumps where the impeller came loose from the pump shaft.
(They kind of still work, but act like you say yours is acting)

OK good. I thought there was an extra boss or threaded hole or something. If it's just the number of vanes then I'll get an 8 vane. I guess i could simply remove the thermostat completely and if I get lots of flow then I'll know for sure it's the thermostat, if there's still "low flow" (without the thermostat) then I'll know it's the water pump....RIGHT???

treblig

 

[mguner]

Sounds more like aerodynamics to me..... Is the rubber seal between the core support and hood still intact? You should be getting a visible flow at T-stat opening temp of considerable volume as well. They may be on to a thermostat issue as well. Never had a water pump issue other than seals or bearing failure.

 

[TrailBeast]

OK good. I thought there was an extra boss or threaded hole or something. If it's just the number of vanes then I'll get an 8 vane. I guess i could simply remove the thermostat completely and if I get lots of flow then I'll know for sure it's the thermostat, if there's still "low flow" (without the thermostat) then I'll know it's the water pump....RIGHT???

treblig

I was going to suggest that, but you sure have a lot of stuff in the way to do twice if you just take it out.
If you do take it out drive it on the hiway before making the decision, because it could still be the radiator or crap in the block causing it.

 

[Treblig]

Sounds more like aerodynamics to me..... Is the rubber seal between the core support and hood still intact? You should be getting a visible flow at T-stat opening temp of considerable volume as well. They may be on to a thermostat issue as well. Never had a water pump issue other than seals or bearing failure.

I had considered air flow at high speeds but since I had little to no flow sitting still with the cap off I think that it eliminates high speed aerodynamics?? Although I don't have the rubber seal but it wouldn't help the water flow. There is almost no flow at all with the cap off just very little movement of the water, like someone very, very gently stirring a cup of coffee. I never seen so little flow before. The only water pump issues I've ever had were, bad bearings, loose pulley (worn bearing), or water pump leak.

treblig

 

[Johnny Dart]

Standard water pumps have 7 impeller vanes and AC pumps have 8.
I opted for 8 since my car generally runs at lower RPM's I figured the extra vane would help the flow at lower speeds.

Actually, cars with AC used 6 vanes, non ac cars used 8 vanes.
The water pump pulley on AC cars are smaller, which spin the pump faster.
Using a 8 vane pump, with an AC pulley can push the water to fast, which causes cavitation.

 

[Treblig]

I was going to suggest that, but you sure have a lot of stuff in the way to do twice if you just take it out.
If you do take it out drive it on the hiway before making the decision, because it could still be the radiator or crap in the block causing it.

There is almost nothing in the way of the thermostat housing. The very first pic I posted has a pretty good view, it looks very easy to get to. Would crap in the block make the water pump have low flow?? The motor had a complete overhaul by the previous owner (came with receipts) I guess I could buy a new 160 degree thermostat (I live in a very, very hot and humid climate) and swap it out that way if I still get low flow I can still assume it's the pump and I won't have remove the thermostat housing again (just the pump).

treblig

 

[Dicer]

Well yes, it could be the thermostat and yes pump impeller freewheeling (rarely). How was the coolant when you drain the radiator and changed the hose, any settlement, maybe rust, dirt? Can you look closely into the top of the radiator and see if you may have crust around your radiator flow tubes? Has anyone mention fan clutch? Drive your car down the highway get it where you feel its getting hot, pull off the road, shut the car down, jump out, open your hood, try to spin the fan, if it freewheels you have a bad fan clutch, a simple test. Normally the fan clutch being hot would have a great resistance to spin. Hope this helps. I have to ask looking at one of your pictures, I notice the by-pass in a large U shape, looking at my car it is mainly L shaped...something maybe kinked?

 

[greg r]

I guess I could buy a new 160 degree thermostat (I live in a very, very hot and humid climate) and swap it out that way if I still get low flow I can still assume it's the pump and I won't have remove the thermostat housing again (just the pump).

treblig

The thermostat sets the floor of the cooling system, not the ceiling which is your problem. I would try another, not remove it. There can be more harm than good with no thermostat to balance flow through the block. Check the radiator fins. Clean them out with compressed air. Check the thermostat in a pan of hot water with a thermometer. See where it begins to open. Simple things 1st.

 

[TrailBeast]

Sounds more like aerodynamics to me..... Is the rubber seal between the core support and hood still intact?

I wondered if I had it backwards, and I coulda swore it was 7 and 8, but you are right.
Strange how that happens.

 

[TrailBeast]

This is the order I would go after that problem with.

Possible air blockage through the radiator (swelled tubes and such)
Thermostat
Water pump (with a block, radiator and heater core flush)
Shoot it

 

[TrailBeast]

The thermostat sets the floor of the cooling system, not the ceiling which is your problem. I would try another, not remove it. There can be more harm than good with no thermostat to balance flow through the block. Check the radiator fins. Clean them out with compressed air. Simple things 1st.

Nobody said leave it out, but just test without.
Doing the thermostat AND water pump with a flush would be the best start, or at the very least pull it for an inspection and still flush it out.
Have you seen some of the pumps with the vanes rotted clear off?
Nasty.

 

[Treblig]

Well yes, it could be the thermostat and yes pump impeller freewheeling (rarely). How was the coolant when you drain the radiator and changed the hose, any settlement, maybe rust, dirt? Can you look closely into the top of the radiator and see if you may have crust around your radiator flow tubes? Has anyone mention fan clutch? Drive your car down the highway get it where you feel its getting hot, pull off the road, shut the car down, jump out, open your hood, try to spin the fan, if it freewheels you have a bad fan clutch, a simple test. Normally the fan clutch being hot would have a great resistance to spin. Hope this helps. I have to ask looking at one of your pictures, I notice the by-pass in a large U shape, looking at my car it is mainly L shaped...something maybe kinked?

The radiator fluid was a little dirty but not bad considering that it had been in there for about two and a half years. I put new water and anti-freeze in there just in case. But to answer your question a little better, the fluid wasn't full of crap and particles...just a little dirty (not crystal clear). I did check the radiator tubes after I emptied the radiator and they looked pretty good. As far as the clutch is concerned, yes it could be failing at high speed but that still wouldn't explain the no/low flow sitting still with the thermostat open?? But I will do that high speed check next time I'm out. That U shaped hose was on there when I bought the car, it does not look correct but it's been working well with the bent hose. We don't hardly use heaters where I live.


Thanks,
treblig

 

[Treblig]

This is the order I would go after that problem with.

Possible air blockage through the radiator (swelled tubes and such)
Thermostat
Water pump (with a block, radiator and heater core flush)
Shoot it

OK, taking it one by one. First, 7 vane pump because I have a small pulley.
Second, possible blockage through radiator....that's possible but since the upper hose empties directly into the top radiator tank I should see lots of turbulence in the water whether the tubes are clogged or not, RIGHT?? Besides, when I looked at the tubes they looked clean and clear.
Third, you're saying flush the system and replace water pump?
Fourth, Shoot it!! Now that's a GREAT IDEA!!!

Treblig

 

[Johnny Dart]

Treblig,
The difference between an AC pump and non AC pump.

AC pumps have 6 vanes.
Non AC pumps have 8 vanes.
AC water pump pulley is smaller than a non AC water pump pulley, which spins the pump faster.
Hope this helps.

 

[greg r]

Nobody said leave it out, but just test without

Anytime you run the engine: around the block, around the country, in a test lab, or your shop; there needs to be some kind of coolant flow control whether a stat, or an orifice plate to make sure flow gets to ALL parts of the block and head and not short circuit back to the pump.

 

[TrailBeast]

OK, taking it one by one. First, 7 vane pump because I have a small pulley.
Second, possible blockage through radiator....that's possible but since the upper hose empties directly into the top radiator tank I should see lots of turbulence in the water whether the tubes are clogged or not, RIGHT?? Besides, when I looked at the tubes they looked clean and clear.
Third, you're saying flush the system and replace water pump?
Fourth, Shoot it!! Now that's a GREAT IDEA!!!

Treblig

Thanks Johnny.

Treblig, what I was concerned about was not what was floating around the water, but what wasn't.
Rust and crap settles in the block passages and can cause hot spots, and since the water pump pretty much has to come off anyway might as well blow out the block and backflush the radiator.

If tubes are plugged you won't see flow because the plugged tubes stops the water from getting to the pump, and also stops water from going out because there is no place for it to go.
Basically the circulation system "stalls" if you will in the whole system.

 

[TrailBeast]

Anytime you run the engine: around the block, around the country, in a test lab, or your shop; there needs to be some kind of coolant flow control whether a stat, or an orifice plate to make sure flow gets to ALL parts of the block and head and not short circuit back to the pump.

If that was the case then every one ever run without a thermostat overheats and that's def not the case.

 

[red67gts]

I like to use Tide HE detergent to flush with. It has helped me with doziers, tractors and cars and is cheap and easy. I have also had impellers slipping on shaft which has caused me lots of problems trying to find cause. I had installed a new water pump on an 8" water pump with a Chevy 292 cu in running on propane and it would ice up and die. I knew I had a new pump so I thought that part was eliminated. I lost lots of sleep and got up one morning at 5 am and took the new pump off and found impeller slipping. Parts house got their eyes burnt

 

[greg r]

then every one ever run without a thermostat overheats

No, that's not where this goes. It's locallized hot areas, particularly exhaust valve area or heads over siamesed cylinders, and also might have castings and restrictions the water would sooner not go around. The engine won't always over heat since there's enough cooler areas to keep things from spiking or boiling over, but you can't know what over heated areas there are unless a tear down shows the wear or have some kind of thermal recording.

 

[Dicer]

I did write a nice post about this problem elsewhere if you like to research my name. I just have not figure out to link things as of yet. And I did upload a few pages from a Chrysler school shop manual that may help you out. I would just try what would be less costly and time consuming first....

 

[SGBARRACUDA]

Have the radiator rodded out and cleaned! What your describing, running hotter at speed and cooler at idle indicates the heat exchange process is not taking place! Your engine produces more heat as the RPM rises. Start with that then trouble shoot from there.