'99 Coolant over flow tank vent line help ? ?

[fashions]

help,
what is the purpose of the vent hose off the top of the coolant over flow tank going into the intake manifold? ( 1999 sl2 dohc )

in an boil over , overheat condition, or over filling the tank, wouldn't coolant get into combustion giving the impression of a bad head gasket to the non saturn tech?

water / combustion chamber....

• was aware of water in the head / block;
• learned of water in "wet" intake manifold at #4 cyl ;
• now learned of hose from overflow tank into the top back of the intake
  manifold against the firewall. ??

[Greg1]

It's not a vent hose. It is just one of the misc. coolant hoses and coolant goes thru the intake not into it.

[fashions]

Originally Posted by Greg1

It's not a vent hose. It is just one of the misc. coolant hoses and coolant goes thru the intake not into it.

thanks greg1,

this hose runs from the top of the overflow tank- into the top back of the intake manifold. it is not the supply line next to the water filled intake port of cyl #4.

when cleaning out the intake manifold, i observed it went into the long runner of the manifold that all the cyl runners collect in.

will get a pict posted tommarrow

[eljefino]

It's a de-aeration hose. Should not have coolant in it but is under the same pressure (up to 15 psi) as the rest of the system, and needs to be intact.

This burps air bubbles out of the top of the engine around back and the air finally eventually escapes through the surge tank cap.

[oseberg]

I think I get it. This vent hose isn't to vent air or fumes from coolant tank, but rather to remove air that might get trapped for some reason in the coolant passages through the intake manifold.

So if you overfill your coolant tank, the excess just leaks out through the cap and all over the place making a mess?

[eljefino]

Exactly. There is nothing under the surge tank that can be damaged by coolant so it will just drip down to pavement.

[fashions]

Originally Posted by eljefino

It's a de-aeration hose. Should not have coolant in it but is under the same pressure (up to 15 psi) as the rest of the system, and needs to be intact.

This burps air bubbles out of the top of the engine around back and the air finally eventually escapes through the surge tank cap.

wouldn't this line from the manifold have a vacuum in it from the intake?

you bring up a good point [ elgefino ] about the water system pressure had not been thinking of that. both the tank and the manifold are open connections with no check valves of any kind.

[ahkistler]

4.5 years later: Anyone know the part number for this hose?

[Greg1]

That line can be replaced with hose sold by the foot at the parts store.

[wolfman]

Originally Posted by Greg1

That line can be replaced with hose sold by the foot at the parts store.

Yep. Rubber fuel line works just fine.

[HikinFool]

I have been reading and researching all of these overheating topics and am still having issues with overheating and excess "backwash". I have a 1997 Saturn SL2, and have replaced thermostat, all hoses (including top and bottom hoses from Overflow tank, the de-aeration tube, radiator, and flushed the entire system. Seems to have helped the overheating issue (only gets really hot 3/4+) after sitting in traffic for extended periods of time. My issue is, once it gets hot and I park, then check coolant level after cool, I need to add coolant. My main concern is that the overflow tank ALWAYS emits excess steam (when cap is on, and when I remove cap, there is a tremendous amount of coolant that is erupting from the tank). I have tried "burping" the system as I have usually done with other vehicles, but have read here that it is not needed with this system.
PLEASE HELP!!!
Thanks!

[billr]

Have you pressure-checked the cap, and cooling system while cold? If the system will hold proper pressure (about 15 to 18 psi), then my best guess s a bad head gasket or cracked block/head. You can rent/borrow a block leak test kit from your FLAPS, usually only paying for the chemical consumed.

You could also try pressurizing the cylinders like in a leak-down test, but that gets tricky as you need to apply as much air pressure as possible (compression is 200 psi, combustion peaks are probably over 1000 psi) and the engine will want to rotate and then open a valve. The only sure way to do this is to remove the cams... You may get *lucky* though, maybe with just 10-50 psi in the cylinder(s) you will start seeing bubbles in the coolant.

PS: Have you measured coolant temp with an immersion (meat/candy) thermometer?

[HikinFool]

Thank you for the reply. Yes, I have pressure and leak tested the system, as well as the cap. I actually just now returned from FLAPS with test kit, and head gasket appears intact!!! All of the other information you provided regarding cylinder testing is WAY above my skill set at this point in time. I may just have to take it to shop, this thing has taxed me beyond belief. Thank you!

[HikinFool]

Also, I have read that this system does NOT need to be burped, is that correct? Coolant temp at overflow is 200 degrees with temp needle between 1/4 and 1/2.

[billr]

It does not need to be burped. but that is because there is a built-in burp line. That is that small (about 5/5" OD) hose going into the top of the coolant reservoir, just below the cap. When the engine is running, you should see a steady flow of coolant coming in there, at the top of the reservoir neck.

[RobertGary1]

Back before cars had there aeration lines it took forever to get all the air out.

[Waiex191]

Are you over filling the system? I'd carry antifreeze and do nothing unless the coolant level light came on. It may find its happy level that way.

[HikinFool]

Thank you all again for the suggestions! I am weeding through all of your ideas (if I have not already). That aeration hose WAS plugged a few weeks ago, but I have since replaced that, and DO see a steady flow of coolant/air entering tank while running. I have considered that I may have overfilled system with coolant, however, I drained and refilled system and was careful to NOT put too much coolant in....My gauges indicate low/hot coolant temp while driving, even though temp gauge is sitting at 1/2. Any other ideas?

[fetchitfido]

Originally Posted by HikinFool

My gauges indicate low/hot coolant temp while driving, even though temp gauge is sitting at 1/2. Any other ideas?

The coolant temp light flash's for low coolant, on steady for over-temp. Either add more coolant or replace the tank (the sensor is baked into the tank) if it's flashing.

As it's a '96+ you should invest in an OBD-II reader that can get live data. I believe they start as low as $20 for the dongle plus a free app on your phone.

[billr]

That "low coolant" sensor got to be pretty flaky on my '94. I bypassed it with a small (100 ohm?) resistor long ago.