TR4/4A TR3/4A Water Pump Housings?

[karls59tr]

I took a water pump from a 4A and mounted it to the pump housing on the 3. The impeller on the pump spins freely when off the housing but when I mounted it to the housing it was extremely stiff to turn the pulley.( It's not rubbing on the outside of the pump in the area where you sometimes have to grind off the housing where it rubs on aftermarket pumps). I removed the pump and added another gasket thinking that the butt end of the impeller was somehow hitting the back of the pump housing.(later looking inside the housing cavity I don't thin k that would be an issue anyway.) The pump pulley is still stiff to turn. I'm going to mount the 4A pump housing to see if that makes a difference. Should the pulley spin just as freely off the housing as it does on?How freely should the pulley spin when everything is set up right?

 

[DanB]

I believe the pumps should be interchangeable, although slightly different. No grease nipple in the later model. But you are right, it should spin freely. Did you have another housing to try?

 

[Darrell_Walker]

It should turn easily, but it won't spin like a wheel would. It should be the same mounted to the housing or not. Perhaps one of the mounting bolts/nuts are rubbing on the pulley?

 

[JerryVV]

That's my thought too. Bolt rubbing

 

[karls59tr]

Wasnt rubbing against the bolts. I took the water pump housing off the 4A and mounted the 4A pump back on to it's original housing and it spins much more freely there. tomorrow I 'll bolt them as a unit on to the 3 and see what happens. Made an odd discovery in that the bypass opening in the 4A housing only has 3/8" opening where the two 3 housings I have both have 5/8"openings! The 3/8 opening in the 4A housing looks like part of the casting and not plugged and drilled out like some have done. I wonder if Triumph decided to reduce the bypass opening by the time they started building 4A's? Were 4A's meant to be run with a " bellows" thermostat like the 3 or did they switch to the regular type thermostat? Victoria British has thermostats for the whole run of TR's for about $4 but shows the "bellows" type thermostat in their diagram and they sell for $100 or sometimes $50 on Ebay so VB must mean the regular ones.

 

[TR3driver]

I wonder if Triumph decided to reduce the bypass opening by the time they started building 4A's? Were 4A's meant to be run with a " bellows" thermostat like the 3 or did they switch to the regular type thermostat?

I forget the change point offhand, but there was a point when the factory started using regular wax pellet thermostats, without the sleeve, in place of the bellows (aneroid) thermostat with the sleeve. ISTR it was earlier than the start of 4A, though, like maybe when the TR4 went to a 7 psi cap in place of the 4 psi used on the TR3.

The non-sleeved thermostats were also an approved supercession for the earlier ones with the sleeves.

 

[karls59tr]

Why would the 4A pump housing have a smaller opening at the bypass than the 3? Is the smaller opening bypass housing meant to be used with the pellet thermostat? I have an aneroid thermostat on order. Is the aneroid thermostat meant to go with the the larger hole bypass housing? Would there be a problem running the aneroid thermostat with the the smaller bypass housing?

 

[JerryVV]

My 1966 4A came with the sleeved thermostat (160) which just gave up last year. Not a bad 45 year run. Replaces with a standard non-sleeved one and all works just fine. Bypass is not blocked. Runs at 180 now. Best improvement that I made however is a Goodparts radiator shroud. In cooler weather with the broken open thermostat I could not get the engine over about 100 degrees at 70mph. I even blocke half of the radiator with a piece of cardboard and it still ran at only 120. Getting air through a good radiator really works!

 

[karls59tr]

How tight should the nyloc pulley bolt be. Could over tightening cause the pulley to spin less freely?

 

[Geo Hahn]

How tight should the nyloc pulley bolt be. Could over tightening cause the pulley to spin less freely?

Not unless the rear edge of the pulley is making contact with the pump body.

 

[TR4nut]

Not unless the rear edge of the pulley is making contact with the pump body.

Which I've seen happen with at least one pump I've had - but you would notice that issue on and off the car.