Hey all, I recently purchased a ’71 Cutlass convertible with a 455 with A/C but disconnected, that seems to have some cooling issues.

The water temp sensor wasn’t connected, so I wanted to install a set of mechanical gauges. Upon draining the radiator for the gauge installation, I noticed the coolant was very dirty. I then decided to flush the engine with a Prestone flush kit.
I had some concerns about the radiator (four core) so I had it checked out by a local radiator shop.
I also installed a 180 stat. The upper and lower hoses are in very good shape, and the lower hose does not collapse. I am keeping the coolant level about 2-3 inches below the radiator neck, I have a new 15lb cap and have no boil-over issues.

The temp readings fluctuate from 190 to 250 when I’m driving 25 to 35 mph. When I drive 40 or higher the temp stabilizes around 190 to 210. When the temp is fluctuating under 35 mph, if I put the car in neutral and rev the engine, the temp stabilizes back to 190-210.

Am I correct in thinking this is an indication of a faulty water pump?

Since I’m pretty sure that I’m going to replace the pump, and I have several part stores nearby (AutoZone, Carquest, O’reillys, and NAPA) is there a certain part number at any of the stores I should look for to ensure I get a good water pump?

 

Might check your fan clutch first.

 

The fan clutch seems to have been recently replaced. I have noticed the 'roar' of air when it engages. I also have a good condition shroud in place.
The A/C coil was pulled out when the compressor and brackets were removed, so there is nothing in front of the radiator but front end grill.
I've watched the coolant flow through the radiator neck, and it seems more on the weak side, but I really don't have anything to compare it to.

 

The water pump is highly unlikely to be the problem, since once it goes bad, it can't magically heal itself. Most water pumps fail by having the bearings go bad, followed by the seals going bad and the dumping of coolant on the ground.

Also, how fast is the temp going up and down? The thermal mass of the engine and coolant makes it physically impossible to have rapid changes in coolant temperature. If the temp is changing rapidly, either you have air pockets in the cooling jacket or a bad temp sender or gauge.

 

This is the same problem that LiquidPower has with his engine, see a thread called "blown head gasket". We have not been able to determine what the problem is. He noticed a swing in temp when he engages the heater valve with the heater core byassed.

Joe - what is the cause of air pockets? Are there large variances in coolant temperature from front to back in the water jacket under normal conditions?

 

I think I got it fixed.
I replaced the water pump and installed a High Performance 180 stat from Mr Gasket. I don't know if it is a High Flow one, but the opening looks alot bigger than the one I pulled out.
I went for a ride after I had finished up, I went the same route I had done in the last several days, only I never went over 35mph this time. The temp held at 190 the entire time.

I don't know for sure which one did the trick, but I'm just happy it's fixed.

The old pump had a cast disk/impeller in it. The 5 'paddles' in the pump were only 3/8 of an inch wide, and maybe 1/2 an inch long. I wish I could have gotten some pics before I took it in. I don't see how it could move any water at all when compared to the new pump.
The new pump is a remanufactured one, with a lifetime warranty, I couldn't wait till next Tuesday for a brand new one. I'm rebuilding the engine over the winter, so it only has to last till November.

 

I didn't have any major swings when I messed with the heater, so I can't help there. The swings I had were happening while just driving along under 35 mph.