Just wondering if anyone had any ideas on a problem i have been having. I have recently bought a 1987 1.7 340 and noticed it had a cracked expansion tank. I had another 1.7 which had the same problem, so i got a new tank and fitted it in the same way, then the problems started.
I let the engine run to clear the air, then took it for a drive. I then noticed there was no return flow to the tank, cleared that, went for another drive on return no water in tank at all. I took cap off all coolant returned, radiator then dripping badly (didn't do it before). The pressure caused one of the hoses to bulge!. I have taken radiator out it seems to be okay.
The system seems to have constant air locks even though it is self bleed, i am wondering if cap is faulty. One minute it has no return flow, then no water in tank, i will replace radiator as it is out, but it has me confused!.
Would be grateful for any ideas, have tried radweld (didn't really want to but new rad expensive!) didn't work. Thanks

When you fitted the new tank did you drill the hole out for the constant flow pipe? If not then this would explain your problem.

I did wonder if that was the problem so i checked and both connections were open, it does return into the tank-sometimes!

To me that would sound like either a blockage or a fault with the pump.

Try removing the cap and get a running hose pipe to hand. Tank the return pipe off and start the engine. Put the hose pipe into header tank to flush the system out.

Thanks for that i will give that a try, i think whilst i wait for new radiator i will take return pipe and t joint under carb off and see if anything there. I have a feeling previous owner had a problem with it, and when i flushed the system through i have moved either sludge or rust out of radiator and into the system. I think the build up of pressure has knackered the radiator!

Could be let us know how you get on.