Rodder

iTrader: (2)

A standard radiator cap has a 2nd valve inside the main valve that will open under a vacuum to allow return from the overflow tank. Here's what it looks like on a Stant 10330:




If you are using a radiator cap with return valve and aren't getting any coolant return from the overflow tank, it's because either the return valve is plugged (stopleak?), or your cooling system is leaking and won't hold any vacuum.

70 LS1

iTrader: (1)

Well I fixed everything.

First I fixed the belt which initially caused all the problems.
Second was to fix the fans. When I first did the conversion 7 years ago, the wiring to the LS temp sensor was faulty and was reading below zero. This made my fans run in fast all the time. I fixed the wiring and now the fans operate as they should, cycling in slow and fast.
Third was to refill the block. When I overheated and lost coolant, I got air into the heads/block. This was causing the temp sensors to read high. I filled and purged the cooling system and started it up this evening.

The temp slowly rose and I could watch the level in the radiator go down when the thermostat opened. I massaged the hoses as suggested and uncapped the steam line from under the throttle body. Once everything was flowing smoothly, I re-capped the steam line, capped the radiator and let it run some more. The temp gage kept rising and around 225 the slow speed fans kicked on. They shut off around 210. I let it run for about 20 more minutes watching the temp cycle.

It would appear my gage is around 10 degrees off (based on the factory fan settings), which is what I expect based on the sender I used.

Thanks to all for your help.

bczee

iTrader: (12)

Well glad to see and hear you back on the road again..

Pop N Wood

iTrader: (1)

Thanks Rodder. The picture of the cap explains it better than I could have.

Also notice there are two rubber seals on that cap, the main one that seals the radiator itself and the second outer one that seals the overflow nipple. This directs the vacuum to the auxiliary tank allowing coolant to be sucked back into the radiator. Get air in the system or like Rodder said have a small leak somewhere and it won't work like it is suppose to.

Ever wonder why radiator auxiliarly tanks have hot and cold level markers on them? Hot and cold doesn't make much sense unless coolant is going in and out.

jojomanx

So whats the deal? Any suggestions? Bad temp gage? Air/steam trapped in the heads? I'm really stumped by the rising water level and gage.[/QUOTE]


Air in the system will look like your pump is not running. Did you replace the belt?