: Coolant Reservoir Overflow Line



Rustbucket350
03-21-12, 01:36 PM
The overflow line (closest to the cap) on my 96 Eldorado is missing from the coolant reservoir. I'm assuming its supposed to connect to something to keep the system pressurized, but I can't seem to find any pictures of it anywhere. If someone could take a picture for me or let me know where its supposed to go that would be awesome.

maeng9981
03-21-12, 02:08 PM
The hose right next to the cap is supposed to be connected to nothing. There should be a length of hose going down to the ground, releasing any overflown coolant to the ground. During the normal operation, there should be no coolant flow through overflow hose.

http://i.imgur.com/iKRxE.jpg

Submariner409
03-21-12, 03:13 PM
The overflow line (closest to the cap) on my 96 Eldorado is missing from the coolant reservoir. I'm assuming its supposed to connect to something to keep the system pressurized, but I can't seem to find any pictures of it anywhere. If someone could take a picture for me or let me know where its supposed to go that would be awesome.

Yep - the overflow hose is just that - excess coolant is drained to the ground in the event of either an overfilled reservoir or an overheat condition (excessive system pressure). The cap itself serves two functions: The spring loaded inner seal plate allows system pressure to build normally to 16 or 18 psi, thus raising the boiling point of the coolant significantly, and system pressure also prevents water pump cavitation ("vapor lock", if you will); there's also a vacuum relief valve built into that inner pressure/spring plate - it allows outside air into the system upon cooldown past the last system cold start condition in order to prevent coolant hose collapse from excess vacuum being pulled in the system due to (cold status) temperature drop. The purge lne is a constant bleed from the cooling system highpoint to keep air bubbles out of the system, thus acting as more insurance against water pump cavitation.

..............at least your car has provision for a coolant overflow line; ours merely vents any excess coolant over the top of the reservoir.......

Proper coolant level, cold, is about halfway up in the reservoir. Never check/fill coolant when warm.