Cooling and bottom hose

[Grumpy21]

Just completed a front end refresh including timing chain water pump and thermostat.

Mostly gone as well as expected with two niggles

I can feel very slight play in the new water pump which probably means it needs replacing!

But more of a question is the temperature of the bottom hose which is not hot at all, barely warm.

Engine runs nicely and with an IR digital thermometer the top hose and rad are around 80 degrees whereas the bottom is around 35

Never checked the bottom hose previously but is the cooling system really that’s good?

[philthehill]

The bottom of the radiator is supposed to be cold.
Hot water passes from the block/head through the thermostat into the top of the radiator. As it cools in the radiator it sinks to the bottom of the radiator were it is picked up by the water pump and pushed around the engine again and then when hot out through the top hose to the radiator and so the cycle continues and continues and continues.
To sum up there is nothing wrong with your cooling system - all is normal.
But change the water pump.

[svenedin]

Very slight play if you pull on the fan belt pulley? Sounds normal. There is slight play like that in a rebuilt dynamo as well. It's end shake and there has to be some.

Top hose should be thermostat opening temperature or close to it so that is normal. Bottom hose temperature much cooler so that is correct too.

Stephen

[Grumpy21]

Thanks both. I thought it was working ok but must be very efficient.

Water pump play is axial not longitudinal. Is rocks side to side, like a worn wheel bearing.

Cheers.

[svenedin]

Thanks both. I thought it was working ok but must be very efficient.

Water pump play is axial not longitudinal. Is rocks side to side, like a worn wheel bearing.

Cheers.

In that case it does sound like the water pump needs replacing. Minispares sell a water pump that they claim is superior to the other modern pumps. Personally, I have been meaning to get my old cast iron water pump professionally overhauled. They last a very long time.

https://www.minispares.com/gwp134evo-su ... ith-bypass

Stephen

[philthehill]

A note on new water pumps. The clearance between impeller and pump body is not always right from new.
The correct clearance should be 0.020" to 0.030". Excessive clearance will reduce the pumps capacity to pump correctly.
With the last pump I fitted the clearance was excessive and I had to press the impeller further onto the shaft to get the clearance correct.
See BMC/BL workshop manual Pt No: AKD530 Section DDD1 for details
Also with a new pump make sure that the depth of impeller is correct for the block being used or the impeller could foul the block.