Pulled my water pump off today to check it out and try to come up with a plan to clean out the coolant passages in the block. There is quite a lot of flaky scaley rusted bits inside, not completely sure of the beat way to clean this out so as to minimize the chances of the radiator getting blocked up withing the first few hundred kms after re-assembly.

Was thinking compressed air down the thermostat opening to try and push the loose bits out through the water pump opening, then after installing the water pump back on (with the outlet blocked) fill it up with vinegar and let sit for 48 hours before flushing it all through with a garden hose.

Any better ideas?

A product like CLR will do a similar job. I'd make sure it holds water first though!

_________________

If you have lots if loose scale around the bottom of the cylinder linings then going in though the welch plugs maybe an option. A magnet works well.

Take out the rear coolant drain and run a hose through the system. Usually the reverse direction of flow. Backflush the heater core as well.

You can also use a piece of panty hoe across the top radiator hose inlet to stop crud getting into the rad. Just keep checking it and cleaning it out until there is no more crap appearing.

I like to run plain rainwater through the system for a few days - dropping and replacing each day.

How does the pump impeller look? Is it a cast iron or pressed-metal version?

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

I would remove the radiator hoses, refit water pump, plug water pump inlet. Then fill to top of head with 1:3 molasses and water mix. Leave 2 or 3 weeks, remove water pump and welch plugs then hose out. Fit new water pump and welch plugs.
I have an S motor on the floor getting this treatment.

I've done this before so I know it works.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

And is the water pump body cast iron or alloy?

_________________

winabbey - I was expecting the pump impeller to look trashed, but was pleasantly surprised by how good it looked. It is a cast type impeller.

timmy201 - I didn't pay much attention, but from memory it had a reasonable weight to it so I am going to say cast iron. Will double check next time I am in the garage!

I had thought of doing so, but was worried about washing it out afterwards. Does washing it out with the garden hose afterward actually get all the softened crud out?

Already did the heater core out of the car, filled it with vinegar for 24 hours and flushed it afterwards, was very happy with the result, did the same with the radiator with similar results.

I did see about using a makeshift filter for the top hose, I will have to do that so I don't kill the radiator!

Also, another question: I measured my belt (well, the belt off the car, not the one around my waist) and it is about 810mm, I see there are three common sizes of 813, 825 and 850mm, the 'cooper s mk1' should be suited to the 850mm belt (larger water pump pulley), what should the diameter of the cooper s water pump pulley be?

The cast iron pumps are the original ones. Definitely worth keeping

_________________

I would guess it is the original, the car only has 50,000 miles on it and has been off the road for 40+ years.

Some good water pump info here - viewtopic.php?f=2&t=95338

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

The Cooper S had a larger generator pulley than standard I think (to reduce generator rpm at high engine rpm. Not sure about the water pump pully, I thought that was the same.


Sent from my iPhone using Tapatalk

_________________

68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

I use this as an example for why I am led to believe the cooper s had a larger water pump pulley:
http://www.classicmotoring.net.au/cmos/index.php?main_page=product_info&cPath=37_156&products_id=37