: STS Coolant Burping Air out of Coolant Question



racal55
11-10-06, 01:00 PM
Hi guys,

I put a new water pump in a '99 STS a few weeks ago and I can not seem to get the sound of rushing water (air in the system) to go away. I have spent days googling online. I have read all of the "coolant" system posts I could find on this site and still haven't figured this problem. out.

The temp gauge is fine - I get good heat - everything seems fine I just can't seem to get the sound of the water circulating to go away.

Am I doing this right? - I'm taking the cap off the surge tank (new cap btw) and letting the car run - after it warms up I then slowly rev the engine up and back down again (to around 2000 rpm). I do get a few bubbles out of the system however I can still feel bubbles in the radiator line. Eventually the coolant in the surge tank will rise and start to overflow and I'll get tons and tons of air burping while it's doing that - then all of the sudden the coolant in the surge tank will start to drop and I think it might even suck the surge tank dry. (Is this re-introducing air into the system???) After this I'll slowly add coolant until it's to the full mark - put the cap on and take it for a ride... Same thing every time!? Rushing water sounds in the heater core.

When I get to the point where the surge tank level drops do I need to be right on top of it adding coolant so it can't suck air?

I'm sorry if this has been answered before and thanks for your help!

nigelb
11-10-06, 01:12 PM
you shouldn't be checking the coolant when the motor is hot, the filler cap helps pressurize the system, which allows the coolant to run at temperatures greater than its boiling point.
what is happening is that when the thermostat opens the coolant in the block meets with air that is at atmospheric pressure and it wants to boil, hence the surge of coolant. you could get seriously burnt.
you should check the coolant when it has cooled to the outside temperature.
the system may take a while to thoroughly bleed out, it's best to check and top up the coolant first thing in the morning or at any other time when the motor has stood for a few hours.
after changing my coolant it took 4 or 5 days befor the level stabilized.

racal55
11-10-06, 01:47 PM
I did what you said the 1st time - then I drove it for 2 weeks - the sound of the air in the coolant system did not go away. I spoke with a Cadillac mechanic and he said the system needed to be bled without the cap on the surge tank...

Ranger
11-10-06, 02:07 PM
The system is self purging. Have you checked the purge line to be sure it is clear and flowing?

racal55
11-10-06, 02:13 PM
That is the line running to the bottom of the surge tank? yes - I get a steady stream of coolant out of it.... How long should it take to self-purge this system? I'm concerned because there sounds like there is a lot of air in there...

Where does the air go if it's a closed system? Does the level in the surge tank decrease as air builds up in the surge tank? I ran it for 2 weeks with no change in the surge tank level...

Ranger
11-10-06, 02:55 PM
No, the purge line runs to the top of the surge tank, above the coolant level. Excess air will be vented overboard via the overflow line when the system exceeds 16 psi. Remove the purge line at the tank and it should spit coolant at idle. Flow will get stronger as RPM is increased. If there is no flow, the line is clogged and the system cannot purge air. It should only take a few revs to 4K to purge the system. Once the air is purged, coolant level should remain constant.

If the purge line is ok, then I would be concerned that your are introducing "air" (exhuast gasses) into the system via a bad head gasket, but if that were the case, I'd expect to see overheating issues.

racal55
11-10-06, 03:06 PM
Ahh ok - I was under the assumption the purge line was at the bottom of the tank... Ok - I'll check that tonight - one more quick question - where is the overflow line?

Thanks Much Ranger!

Ranger
11-10-06, 03:45 PM
The overflow line is right under the cap. Only about a foot long and just dumps overboard.

racal55
11-10-06, 04:02 PM
Thanks Ranger - I'll check this out tonight... funny I don't remember seeing an overflow line on this thing....

Thanks again!

nigelb
11-10-06, 04:33 PM
the 98 on cars have a different surge tank that does not have the overflow pipe.
also the filling and bleeding proceedure for the later cars does not include the part about raising the engine speed to 3000rpm 5 times as per the earlier models, the FSM for my '97 car details this but the FSM for the '00 does not.
the tanks are on different sides of the car.
the system is supposed to be self bleeding via the surge inlet and outlet pipes.
the FSM states that the engine should be switched off when the lower radiator hose becomes hot then allowed to cool before checking the coolant level.
when i changed my coolant i did notice that the radiator hose that runs across the front of the car took a while to get completely hot but i never heard the sound of water rushing.

racal55
11-10-06, 06:15 PM
Ok - I have the surge tank without the overflow tube. I pulled the top tube off at the surge tank - when I run the car where is the coolant supposed to come from - the car side - or the surge tank side? I was getting nothing at all until I cleaned a the small opening in the surge tank side with a wire - now I get coolant streaming out of there at idle... Does this sound right?

nigelb
11-10-06, 07:10 PM
I can honestly say that i have never run my car with the small top hose removed. it's midnite here, i'm interested in the flow so i'll look at mine in the morning and let you know where the coolant comes from.
the small top hose helps with the bleeding process and if the outlet on the tank was blocked then that might be the cause of your trapped air.
i do not think that the surge tank actually forms part of the pumped coolant system as such, i think that the small top pipe is basically a bleed tube that allows air and maybe excess water pressure an alternative route.
the surge tank is meant to be removed and flushed out at the same time as the coolant is changed.
i did mine 2 years ago when i got the car and i redid it recently, there is quite a lot of crud that gets in the tank, most probably from the coolant pellets that you have to use.

racal55
11-10-06, 07:19 PM
Thanks much !!

Ranger
11-10-06, 08:54 PM
Now that Nigel mentions it, I guess the screw on caps have a vent built in. The old style caps have the overflow tube. The purge line flow is FROM the engine TO the surge tank. If you remove the line at the tank, you should get flow from the line, not from the tank. This should be done with the engine cold for obvious reasons.

nigelb
11-11-06, 08:15 AM
this morning i started the engine and let the idle speed fall back to normal from the cold start before taking the pipe off the surge tank.
the coolant came out of the pipe from the engine but at a fairly low speed.

if you have coolant coming out of the surge tank from the small pipe fitting then you probably have too much coolant in the tank.
the tank is a two part design, the top is black, the bottom is kinda see through.
the coolant should be to the top of the see through part, if your tank is a bit dirty it can be hard to see, in the past i have shone a torch through the filler neck to highlight the fluid.

racal55
11-11-06, 01:47 PM
Ok - the purge line WAS clogged - I was getting no coolant out of it from the motor. I ran some shop air into it until I got bubbles into the surge tank and tried it again. Now I'm getting flow from the purge line as you guys stated. I took it for 2 drives today - about 3 hours apart - I'm still getting some "water running sounds - and gurgling sounds " when I accelerate and when I run the engine at about 2k RPM - for about 15 seconds then they go away. but I at least feel better knowing the purge line WAS clogged and now it's not. I'll run it for a few days and check the coolant when it's cold (it was down already the 2nd time I drove it today so I know it purged some air out). I'll drive it a few days and check the coolant cold and let you guys know how it comes out. Thank you VERY much for all your help!

Chris

dkozloski
11-11-06, 02:57 PM
Ok - the purge line WAS clogged - I was getting no coolant out of it from the motor. I ran some shop air into it until I got bubbles into the surge tank and tried it again. Now I'm getting flow from the purge line as you guys stated. I took it for 2 drives today - about 3 hours apart - I'm still getting some "water running sounds - and gurgling sounds " when I accelerate and when I run the engine at about 2k RPM - for about 15 seconds then they go away. but I at least feel better knowing the purge line WAS clogged and now it's not. I'll run it for a few days and check the coolant when it's cold (it was down already the 2nd time I drove it today so I know it purged some air out). I'll drive it a few days and check the coolant cold and let you guys know how it comes out. Thank you VERY much for all your help!

Chris
A piece of cord from a string trimmer is a good tool for unclogging lines. If you have a hard clog, a piece of speedometer cable in an electric drill should do the job.

Ranger
11-11-06, 04:49 PM
Run the RPM up to about 4K a few times. That should purge the air.

racal55
11-12-06, 03:24 PM
You guys are the greatest! That worked perfectly - no more sound of water! Thank you for all of your help!!!!!!!!!

nigelb
11-12-06, 04:09 PM
i'm pleased that you found that the info helped solve your problem.
thanks for letting us know that the problem is solved.

Ranger
11-12-06, 04:56 PM
:thumbsup:

racal55
11-15-06, 04:59 PM
Guess what? The sound of water is coming back! It's not a gurgling like before - it sounds more like a flowing noise from 1600 to about 2200 rpm... I'll be checking the purge line tonight to see if it's clogged again... Ugh - I'll keep you guys posted.

nigelb
11-16-06, 04:06 AM
where are you when you hear the noise?
are you sitting in the car or are you outside with the hood open?
if you are in the car then you are hearing the coolant in the heater core which may have a partial blockage, disconnect the hoses under the hood and flush with a hosepipe.

racal55
11-16-06, 08:27 AM
Yep - I'm inside the car - the sound runs from driver side to passenger side - most pronounced upon an accelerating from a stop through a left turn. This might last 5 - 10 seconds and the the sound goes away. Also sitting the the driveway if I rev the car up slowly I hear the sound from about 1500 rpm through 2200 rpm - then it goes away... Once the sound goes away I only seem to hear it again after the car has idled for 10 seconds or so. I'm not loosing any coolant - the purge line is flowing and the car is not overheating and the heater works fine. I think you might be right - it sort of sounds like the coolant is having to "work it's way around" something in the heater core... I'm going out of town with the car tomorrow so I won't have time to try to flush the heater core until maybe Sunday... I'll be putting 600 miles on it this weekend so I'll just keep an eye on the situation.

I've seen quite a few threads with this same sound however not one has posted a solution - bummer. I'll let you know how it goes.

Thanks very much - I appreciate your time and comments!

Ranger
11-16-06, 07:27 PM
I agree with Nigel. Flush the core. That should take care of it.

racal55
12-04-06, 12:37 PM
Thanks again for the help guys! It's soooo cold out here now I'm going to wait for warmer weather before I tackle flushing the heater core... Everything seems to be working fine except for this noise - I'm going to let it ride..

I'd post back when I do get around to flushing this thing!

ilovemysportycadilla
04-18-07, 04:46 PM
Hey guys, I am having the same problem. Which hoses do you disconnect to flush the heater core? I hear the noise while in the car, and it sounds like its under the dash.

Ranger
04-18-07, 08:33 PM
The two 3/4" hoses that come out of the firewall.