bluzrocker

what is a closed cap? seems like the 15lb cap is not tight when fully rotated...am I missing something?
pls educate me on that cap...have a recovery tank and thats where the over flow is plumed..and 15lb cap on both rad and recovery tank am I missing something?

JohnZ

What do you mean by "external overflow"? The stock BB setup uses a thinwall rubber hose from the overflow nipple below the cap on the radiator filler neck that just hangs straight down next to the frame, so excess coolant just dribbles on the pavement. 66's didn't have any sort of external coolant recovery tank - that didn't start until the C3 era.

The correct cap is an RC-15 (15# pressure rating).

Mike Ward

No Corvette came from the factory with two radiator caps. No C2 Corvette came equipped with a recovery tank. (?)

bluzrocker

I added the aluminum over flow tank because I kept loosing fluid and got caught several times with the rad low..this car did not have one originally..I just want to keep the rad full as possible and not have anti freeze on carpet on garage floor...the radiator thats in now is a new aluminum Harrison w/ out the side tanks built in as per most BB radiators..just a plain rad w/ the 1/4' rubber line to discharge to the ground

JohnZ

I'm still confused - got pics of your radiator and added overflow tank setup so we can see what's going on?

bluzrocker

I am aware that BB did not come w/ this expansion tank I purchased this from paragon and added it to keep over flow off the garage floor and continually adding coolant to keep radiator full as possible...if members here think it wont work I can remove it and replace one 3/4' heater hose and return it to original configuration...with just the 1/4" rubber line to discharge to the ground...any suggestions or comments?

TX

Nowhere Man

Your creating a problem that should not be there. Remove that tank and plumb it like the factory. Read JohnZ article on cooling and drive it

Mike Ward

There's your problem. The rad should have 2-3" of air space to allow for expansion. Never full to the brim.

Nowhere Man

So the line on the tank that says fill here cold is there for reason

bluzrocker

thanks for the tip I have been filling to the top, and that makes sense.. now if I have any more trouble I'll eliminate the expansion tank...as it is plumbed TEE'ed into the 3/4" water line from the water pump to the heater..
to all who spent time thinking and replying I do appreciate the help..I did look over the rad and did not see a line to fill max but now there is 3' of air gap to top of rad fill

bluzrocker

Want to thank you for pointing that out , iv'e been shooting my self in the foot the entire time. and want you to know I listen and learn all the time from guys like you ...tx again

Bluzrocker

JohnZ

If you keep "topping it off", it'll keep puking, 'cuz there's no space in the system for expansion; don't top it off, and it won't puke any more. When it stops puking, it's found its "happy level" (which will be 2"-3" below the filler neck on the radiator).

We still don't know what you're using for a radiator - got a photo? There's no such thing as a Harrison aluminum BB radiator (except for the one used on the '65 396 and the L-88, which required special radiator supports).

bluzrocker

My mistake it's a Dewitt BB aluminum direct replacement..was thinking of the Harrison dash place in Florida...sorry Part #1139066M And yes I know (thanks to members tips) about over filling and was making the problem myself by doing that.. the expansion tank is from Zip/paragon Part# 2232 and it's plumbed into the 3/4" heater hose w/ a tee and a 15LB. cap...is this going to work ?

JohnZ

No, it won't - you have one system fighting another one. Remove the expansion tank and tee and let the radiator do its job.

bluzrocker

Thanks for the advice...looks like I out smarted myself ....do appreciate the advice and solutions will be a easy fix....remove and replace one 3/4" H20 hose and BB will be happy...ok removed the expansion tank replaced the hose and returned to original configuration more room @ battery ...too....and thanks to all who responded

Nitrous 74

I have a similar issue with the 66 I recently purchased.
What should I do here? Run an "open" 0PSI cap on the radiator, leave pressure caps on both or remove the expansion tank? Cooling seems to be working fine as is with the two caps.

Vet65te

Same answer as JohnZ gave in post #14 above, if the non-stock type radiator you're running has a pressure cap, which it appears to have, then you don't need the expansion tank.
Nice looking 66, have you posted some pics of it?
Mike T - Prescott AZ

DansYellow66

A regular radiator cap vents excess coolent off but won't allow it to return when the engine cools off. You are just using the expansion tank as a catch can and would eventually have to empty it - although with a regular radiator cap on the expansion tank they are just fighting each other so who knows?

A newer coolant recovery cooling system uses a different type of radiator cap that not only vents out, but allows coolant to return to the radiator as it cools and contracts. The overflow recovery tank is not tightly sealed with a radiator cap and vents air as coolant flows in and then back to the radiator.

Nitrous 74

Thanks Mike T, I'll post some pics to my profile. It is pretty nice, but like every car I've ever purchased there are always a few things that need sorting out. Right in the middle of a borgeson steering conversion, finishing the unfinished A/C install by the previous owner then basically un-tarting up the engine compartment. Going for a more stock look, but not worried about being 100% correct because it's not numbers matching.

If I can run without the expansion tank then I'd love to be able to use the expansion tank as the a recovery tank (plug off the bottom connection and use 0psi or gutted cap), I wonder if I could somehow make the inlet into a pickup.

I don't quite understand all the comments on two systems fighting? Wouldn't this still be one system? If the radiator cap opens, then it simply connects the already connected expansion tank in an additional way. The real cap that keeps the system closed would then be the expansion tank cap, so really the radiator cap is irrelevant.

I must admit I do like the high fill point on the system that the expansion tank provides, and a little extra coolant capacity I have found can sometimes go a long way to keeping an engine cool.

Badelky

I have a 66' L-72 which was always running hot in the So-Cal summer weather, so I did in fact add an expansion tank with a 18lb cap, used a 15lb cap on the radiator, high flow water pump, L-88 style water neck and NO thermostat with 50/50 Mercedes coolant.

This Summer in 98+ degree weather the car never got above 180.

It's been 2 Summers and the car has never come close to overheating once in any condition.