THERMOSTAT FILLER

[billwill]

Stu,
We're talking mostly about the Coolex neck, which is what I have . ANd now that I've got it to stop leaking, I'm finding that the coolant that goes into the overflow bottle isn't getting drawn back into the engine as it cools (and yes, the tube goes to the bottom of the bottle). Kind of annoying.

Mine does that too, I guess it means that somewhere there is a leak which prefers to let air into the coolant system, rather than suck back the coolant from the overflow tank. Since there is no sign of a leak in the other direction, i.e. coolant out, I think it might be the seal in the waterpump.

What is very important and might be your problem is that the top seal of the radiator cap must be near perfect, so you may need to fit a new rubber washer there and maybe use emery cloth on a flat tool to 'flatten' the top surface of the radiator cap mount (the revised thermostat housing).

[alan.barker]

Maybe check the distance between the 2 Seal Landings and compare the Rad Cap distance
Alan

[SENC]

I have the coolex, and did not have the quality issue Veg reported - mine looked good and sealed fine with no extra heroics necessary.

Since I already had a functioning recoup bottle on the radiator itself, I left that one functional rather than running a longer tube to the coolex. I have a 7lb cap on the radiator filler and a 13lb cap on the coolex filler to make sure the right one is in play. If you have a lower or similarly rated cap still on the radiator as the coolex, that could be your return air leak.

[The Veg]

Both my caps are new, a non-valve cap on the radiator and I want to say 13 or 14 lb on the Coolex, which has already been subjected to a dressing of the sealing surfaces but who knows, maybe not enough. But no evidence of water getting out at this point that I have seen.

[billwill]

Both my caps are new, a non-valve cap on the radiator and I want to say 13 or 14 lb on the Coolex, which has already been subjected to a dressing of the sealing surfaces but who knows, maybe not enough. But no evidence of water getting out at this point that I have seen.

Non-valve cap on the Rad, but have you sealed off whichever overflow pipe is not in use?

[stugilmour]

Best way I found to check for the small leaks was to pressurize the system with a coolant tester hand pump and let the car sit for several hours. Then hunt for drips. Any small leak and, as Bill mentioned, air enters the system instead of the coolant from the bottle. The testing kits typically include an attachment to test the cap as well. As mentioned I never did get the Elan to work reliability.

https://www.stant.com/files/3514/0979/5 ... apters.pdf

HTH

[SENC]

Veg - I'd check the 2ndary vacuum valve on your cap, just to make sure it isn't stuck and preventing the vacuum from pulling coolant back. Then maybe try the 10lb cap spec'd for a +2 (or even a 7lb) - I don't know whether the return valves on these caps have similar strength differences as the overflow springs, but on the assumption they do it may be that the other bits of the cooling system allow air back in before the return valve of a 13lb cap pulls in fluid.

[billwill]

o it may be that the other bits of the cooling system allow air back in before the return valve of a 13lb cap pulls in fluid.

That's why I said check that the UNUSED overflow pipe is blocked. The top seal of that filler cap should then prevent air entering via that route.

[Donels]

I had an in line filler made to replicate the function of the NLA Clive Boy neck, see picture, then found you can buy the same thing on eBay very cheaply.

[The Veg]

o it may be that the other bits of the cooling system allow air back in before the return valve of a 13lb cap pulls in fluid.

That's why I said check that the UNUSED overflow pipe is blocked. The top seal of that filler cap should then prevent air entering via that route.

The un-used one is on the same neck as the non-valve cap, on the rad.

[h20hamelan]

[quote="Donels"]I had an in line filler made to replicate the function of the NLA Clive Boy neck, see picture, then found you can buy the same thing on eBay very cheaply.

I sort of doubt the ebay ones have any sort of quality

[alan.barker]

Quality is the problem on the cast Thermostat Filler
I can't see ebay Top Hose filler being worse and it's cheaper
Alan

[billwill]

o it may be that the other bits of the cooling system allow air back in before the return valve of a 13lb cap pulls in fluid.

That's why I said check that the UNUSED overflow pipe is blocked. The top seal of that filler cap should then prevent air entering via that route.

The un-used one is on the same neck as the non-valve cap, on the rad.

Precisely why it needs to be blocked off. If the Rad Cap does not have the lower portion, i.e. is just one flat disk with a rubber seal then the overflow entry/pipe will expose the coolant directly to atmospheric pressure.

[The Veg]

If that was true then coolant would be spewing from it whenever pressure exists in the system and that is not the case. That cap has the inner and outer seals, just no valve to allow the inner seal to be released

[SENC]

I think I was tracking with Bill, that you were using a blanking cap, which would not seal until at the cap. Are you saying you have a cap that seals at the lower flange, but does not have a pressure spring? I wasn't aware of those - do they not have the return valve, as well?