Water pump

[Pieter Kanitz]

Hello Corvette Experts!

I've got a waterpump question, its about a standard waterpump on a 327 cu. I like to know how strong the spring valve is that is placed in the waterpump. It passes fluid (when the pressure is too high) through 2 small holes in the front of the pump (under the pulley).
I like to know this in order to put a radiator cap on the radiator wich has less LB's so that the water will escape throug the overflow pipe instead of dripping out of the pump onto the crankshaft pulley, and when spinning making a terrible mess. (the system has no expansion tank)

Thanks in advance

Pieter

[Joe L.]

Re: Water pump

Pieter-----

There is no "spring valve" on a Corvette (or, any other Chevrolet) waterpump. What you are referring to is the water pump SEAL ASSEMBLY. This is a multi-part assembly which includes, among other parts, a spring, a carbon seal, and a ceramic seat. The carbon seal is pressed against the ceramic seat by action of the spring. The ceramic seat rotates with the shaft/impeller assembly while the carbon seal remains stationary. The interface between the carbon seal and ceramic seat is what prevent water from leaking out of the pump.

The holes that you describe are weep holes. A SEAL ASSEMBLY of the sort described above will have a certain amount of leakage (or, "weepage") associated with it. When new, the weepage is usually minimal. As the pump components, including the bearing/shaft assembly and the seal assembly age and wear, there may be more weepage.

If either the carbon seal, ceramic seat, or rubber bellows component of the seal assembly fails, then there will be a large amount of fluid loss through the weep holes.

Installing a lower pressure rating radiator cap will not significantly, if at all, reduce weepage at the water pump weep hole(s). If you want to do that, your best bet is to get the pump rebuilt or install a new or rebuilt pump. If there is enough weepage at the hole(s) to cause a "terrible mess", then I'd say the pump is definitely in need of rebuilding or replacement.

[Pieter Kanitz]

Re: Water pump

Thanks,

I know it isnt exactly a spring valve but i didn't know how to call it since my english word vocabulary is not big enough. But thanks for explaining I alltough I thought that it was some sort of over pressure valve, why else would one put 2 holes in the casting? Everything must be completely dry and clean since my engine is in a clean room state. I rebuilded the pump with parts from long island. But a few drips from the designed dripholes dripping onto the pulley just making a mess.
Does it really have nothing to do with the fact that I started the engine for first time with a completely full radiator and a strong raditor cap installed. I would say the fluid goes the easiest way!
Could you point out to what height level the radiator (a copper c1 one) should be filled for normal road use. (eg 1 inch under filler cap)
Do you also know how much lbs a normal cap on a radiatro as described is fitted with?

Regards pieter

[Joe L.]

Re: Water pump

Pieter-----

Well, now you have a new term for your English vocabulary. It's water pump seal assembly. Actually, this type of seal is called a MECHANICAL SEAL. It is used in all sorts of pump assemblies, not just automotive waterpumps.

The hole or holes found at the base of the snout are weep holes. There is always a certain amount of weepage from this sort of seal and the hole provides a path for the weepage to escape the pump instead of otherwise accumulating on the dry side of the seal. Also, there may be some pressure equalizing purpose for the holes.

Sometimes, new or rebuilt waterpumps will weep a bit at first. This is because the carbon-ceramic seal surfaces need to "bed in" and this might require a little bit of time. There's also the possibility that the seal in the pump is not right. If there's enough weepage to create the mess you describe, I would tend to think this way.

The level of the radiator should be approximately 1" below the filler cap in a system without coolant recovery (like ALL Corvettes through the 1972 model year). However, the only result of having the system too full should be overflow at the filler neck overflow port----not "overflow" at the weep holes of the water pump. A higher than normal pressure cap should not cause the problem, either. Corvette pressure caps ranged from 7 PSI to 15 PSI over the 55-70 period. However, small block waterpump seal assemblies did not change significantly over the same period. So, the same seal that worked with a 7 PSI cap was also used with a 15 PSI cap.

Most C1 Corvettes used a 7 PSI cap. 58-59 with FI and some later C1's used a 13 lb cap. Regardless of which cap is used, I don't think that it should have any significant effect on leakage at the waterpump weep holes.

I've included a picture below of a waterpump seal assembly. This is a standard GM type seal for 55-70 waterpumps.

[Joe L.]

Another Photo

Here's a top view of the seal assembly. The piece on the left contains the seal frame, spring, bellows, and carbon seat. The part on the right is the ceramic seat with integral sealing washer.