This is an extension of my input into the Coolant Question Thread. If you have read the aforementioned thread, you will know that I am pulling my hair out trying to get coolant through my heater.

I have already changed the heater valve for a new unit and checked good flow through the matrix.

Through a lot of fiddling, I have had some small success, but the problem is nowhere near solved.

Today I removed the water pump to check clearance of the impeller on the housing. and I did find a large clump of junk blocking the spigot for the heater connection. So that is where SOME of the problem is solved.

Now for my confusion. In the process of cleaning the pump housing, in particular the heater spigot flange area, I found that there are no water ports or passages in the pump housing for water to enter the spigot! The spigot also has a take off pipe(small diameter) that leads to the carbie for the choke. The other pipe on the choke discharges to the thermostat housing.

Haynes tells me that water flows "from the water pump to the heater and returns to the water manifold". This seems to be true due to the choke pipes mentioned above. If there are no ports or passgaes, HOW DOES THIS HAPPEN? I am not a degree qualified engineer, nor am I a mechanical dunce. The construction of the housing suggests that if i drilled a port straight through, the opening would be on the suction side of the pump, thereby putting lie to the Haynes description.

Maybe if the Haynes had a diagram of the cooling system I might nut this out. Does ANYONE have such a diagram?

Should I drill or is it supposed to cast this way?

AAAAAHHHHHHHHHH!!:bang:

On my car the tube to the heater comes from the main pipe outlet at the back of the waterpump (that runs alongside the engine underneath the exhaust manifold) and the return is into the housing of the thermostat - but this pipe also splits off into the top inlet of the header tank.....

Looks like you've hit the jackpot Dogdda The original water pump housing for 1300's should have a through port to the heater - 1500 cars don't have this as the equivalent hose connects onto the bypass metal pipe via a new small take-off that 1300 cars don't have. I think the reason for this is that the 1500 auto-choke connects off the new bypass pipe as well then back onto the inlet manifold. 1300's (without auto-choke) have a hose between inlet manifold and a take-off on top of thermostat housing - there is no take-off on thermostat housing top for 1500 cars

Anyway, looks like pump housing has been replaced with a later 1500 type at some point - most aftermarket ones use the same casting just not drilled through as you suspect - so go ahead a make a through hole (10mm at most?) and watch out for swarf so best to block inside pump before hand.

Ics19 is spot on!

Doggda, the Haynes BoL is not correct (again). The coolant pump only pumps coolant into the block and head, there are no other outlets. The feed to the heater comes from the head. If you drill that blind boss, as you said it should pop out on the suction side of the rotor. You should drill it 10 to 12 mm.

Congratulations on sorting out the problem!

Cheers R

Thanks so much folks. I had the pump apart on the bench so didn't have to beware of swarf. I drilled to the same diameter as the spigot (approx 12mm). Tomorrow I will put it all back together and see what happens, though I am confident we have sussed it out.

Thanx again to Ics19 and racheljf. Love Ya Work!

SUCCESS!!!

Today I put everything back together and after fixing a large leak caused by a warped flange on the pump suction pipe (originally fixed with a ****load of Silastic by somebody), I now have a watertight, fully functioning coolant system - including heater!

Though now I look back through the forums, I think littlephil had a similar drama - D'oh! shoulda checked there first - thanx agin folks.