I've installed a flush/fill fitting in the 5/8 hose line going to the tb. This seemed like the highest spot in the cooling system and so the best place to put a little fill point. When the car is sitting and cold most any air in the system should eventually work it's way up to the fill fitting. I thought by doing this I could get every last bit of air out. Put this in yesterday filled it up thru the rad and topped it off thru the new fill point. Drove the car around and everything seemed fine. Made a mental note to remove the new fill point cap and check the level next morning. Checked it this am and no water showing in new fill spot. OK, just need to top it off a little. 1 qt later I'm wondering what the heck is going on. Check the over flow res and it's way up from yesterday. Keep adding more water and am watching the reservoir level go up. It has to be flowing back thru the new Stant flip lever cap I put on a month ago. Go get the old cap (never throw out old parts), which says AC on it so I figure it's the original cap, put it on, and continue filling thru the high fill spot. Reservoir quits rising and the water tops off. I wish I still had the receipt for the cap cause I sure would take it back. I had thought that all rad necks were the same. If so then the cap has to be bad.

Has anybody else had problems with aftermarket rad caps not working properly? Could this be one of those cooling system head scratchers that people have a hard time figuring out? Hope my install of the high fill point and experience with the aftermarket rad cap can help someone out.

 

Possibly you didn't get all the air out of the system. You could monitor it for a while and see if the air eventually burps out.

 

I'm not a L98 owner but, I've learned here from Pete K to lift the Vette by the front cross member the highest possible and that will allow the trap air to find its way out.

 

The reason I put the fill fitting in was so I didn't have to jack the front of the Vette up to make sure there no air in the system. It also makes a quick place to check for air ( as long as there is no pressure in the system). If I hadn't done this I would never have found out the new rad cap I bought was no good.

Moon

 

Have never seen a lever vent cap for a closed cooling system. The cap may be ok for a early style cooling system that has a puke tube @ the radiator fill & does not have a coolant recovery container.

The label on the cap should indicate what type of cooling system it was designed for.

 

Churchkey, you got me thinking so I went and checked the lever cap. Didn't say a word about overflow or no overflow. Looked at 5 different brands of caps on Summit's site and the word overflow wasn't mentioned in any of the cap descriptions. When I bought the cap I didn't even think about it.

Which brings me to the question; how does the rad cap let coolant from the overflow tank back into the cooling system as the car cools down? Is there a little one way flap built into the cap?

Ran the car after putting the old cap back on and topping off the coolant. Went out 4 hrs later and coolant was still right up in the new fill fitting. I just thought of the term I couldn't remember before. Remote fill. That's what the fill fitting really is. Lot of places where a remote fill is used. Race cars being one.

Moon

 

Non recovery systems use a cap that holds pressure however it vents to the atmosphere and allows air into the system as the fluid cools and has less volume.

Non recovery systems will be an inch or so low on coolant if the system is checked when the engine is cold.

Closed system caps are not vented and pull coolant back to the system from the recovery tank as the system cools.

Closed system caps are normally imprinted with the words "for closed systems" on the top of the cap. Suggest checking the old AC cap for the closed system identification. My AC cap has it.

If the lever cap does not have the closed system identification it is for a non recovery system.

Good luck.

BTW: Check the Summit "details" link on the rad cap you select. Read the "notes" at the end of the description. If ir does not state that the cap is for a closed system its for a standard old style cooling system.

Here's a description of one of the caps:

Radiator Cap Shape Round
Gauge Included No
Cap Material Steel
Cap Finish Natural
Quantity Sold individually.
Notes This is a recovery style radiator cap.

 

never new that I thought a cap
was a cap just different lbs

 

As a stock system cools, the coolant in the system "contracts" creating a vacuum and coolant is pulled back into the system from the reservoir. The reservoir cap is vented to allow the fluid level to increase and decrease.

 

I've always used a Stant lever cap. That way I can release any pressure in the system before removing the cap. The stock cap has no lever. So, you have to wait till it is stone cold before you can remove the cap.

 

How about some pics of your work???

 

Here's some pics

[img=http://img254.imageshack.us/img254/4889/remotefill1.th.jpg]
[img=http://img694.imageshack.us/img694/3993/remotefill3.th.jpg]


not much to it. But it does seem to be the high point of the coolant system which, I think, is the best place to have the fill.

Moon

Please excuse the dirty engine. That will be taken care of this winter.

 

Thats where I installed my flush and fill kit. Works great. Just make sure to burp the system to get all the air out. You'll be suprised how much more coolant will go in when you get ALL the air out.

 

That makes another place to have a coolant leak. I like burping it the old fashion way by holding the throttle open while topping off the radiator.

 

GM really should have put a remote fill in at the factory. Anytime the highest point in the coolant system is higher than the rad cap a remote fill should be at that point.

Moon