still under pressure?

Hi I have a 2000 Venture. I drove it to work and about a minute I had cool air coming out then back to hot. Happened the last couple days. Only for a few seconds to about a minute. It takes me about 30 minutes to get to work. I went out after work and went to open the radiator cap and it pushed some antifreeze back up in the over flow. I shut it as fast as I heard that noise. Is that normal having pressure in the system after sitting almost 9 hours and it's 19 F. degrees out??? :confused: I was going to open it to see if it was still full where I put antifreeze 3 days ago. Thinking about changing thermostat and temp. sensor this Saturday. I did flush the system and also flushed just the heater core about 4 days after I flushed the system. I put the green Prestone in it.
Thanks, Dan

GuttaFixit, Doe your venture have a coolant reservoir tank with a cap on it? This is where you need to be adding coolant if equipped. Probably normal to have some residual pressure in a sealed system also make sure you bleed the system of trapped air.

Yes it has an over flow tank. I have a lot of antifreeze in it. After I opened the bleeder screws I still had to add antifreeze in the radiator. For some reason it wasn't taking it from the over flow tank. I had to drain some out. It's still over the cold full mark. I've gone out in the mornings 2 days in a row (I think) and opened the radiator cap and nothing. No pressure. I can look down the radiator to see where the antifreeze is. I'll add some if it needs it. Just wondering about the pressure because when I got out of work 1 day it still had all kinds of pressure. It pushed the antifreeze back up in the over flow tank when I tried to open the radiator cap. I changed the thermostat yesterday. So I'll mess with it the next couple days. Bleeding the lines and all.
Dan

Dan I see what you mean about the left over pressure, could be something but I've seen that before in several vehicles with nothing wrong? Let us know. good luck.

GuttaFixit, Doe your venture have a coolant reservoir tank with a cap on it? This is where you need to be adding coolant if equipped. Probably normal to have some residual pressure in a sealed system also make sure you bleed the system of trapped air.

what he means is do you have the GM tyle overflow tank w/ built-in pressue cap?

http://info.rockauto.com/getimage/getimage.php?imagekey=251913&imageurl=http%3A//images.wrenchead.com/smartpages/partinfo_resize/DUS/RC27.jpg

http://www.2carpros.com/images/articles/engine/cooling/radiator_cap/radiator_cap.jpg

or just the standard cap on top of the radiator? (overflow tank not pressurized)

http://jeromeo.hubpages.com/hub/Why-its-important-to-change-your-Radiator-Cap

that last link i posted is a good reason to change out the standard radiator cap

if you have the first type that i've posted, i think it's normal (others with this type of coolant system should chime in to confirm):2cents:

I have a radiator cap and then have an over flow tank. I took a pic of the motor. This weekend I will go and buy a new radiator cap though after reading your post and that web site. Thank you
I over heated on the way home today. Had to pull over on the interstate and opened the both bleeder screws. The one on the thermostat housing pissed out air for about 30 to 45 seconds solid. I couldn't believe it. THEN my socket and extension fell off and the bleeder screw went with it. While it's still pissing out air. I looked and looked and finally found the screw under the van. Just glad there was no antifreeze coming out while I lost the screw.
Thanks Dan

I think you still have air trapped in the system. I would elevate the front end, either on ramps, hill, jack etc. Remove the cap off the radiator. Put your heat control on full heat. Start the car and let it warm up. Monitor coolant level in the radiator. Some vehicles can take up to 30 mins to burp the system. Ditto on replacing the radiator cap.

I have a radiator cap and then have an over flow tank. I took a pic of the motor. This weekend I will go and buy a new radiator cap though after reading your post and that web site. Thank you

np, you start at the cheapest option & hope it works, especially his with that website explaining some of those reasons...


I over heated on the way home today. Had to pull over on the interstate and opened the both bleeder screws. The one on the thermostat housing pissed out air for about 30 to 45 seconds solid. I couldn't believe it... Just glad there was no antifreeze coming out while I lost the screw.

Thanks Dan

um, now i'm concerned! not a good thing at all!

those bleeder screws shouldn't have been opened while hot; those are used during a drain-flush-refill process of the cooling system only -- open while cool only & fill fluid until steady stream comes out of 'em-- glad that those didn't break while doing so when you overheated.

agree that you may have to elevate the front of the vehicle to ensure that you "burp" the system from any air pockets, making sure that your heater is on full blast & hot so air won't be trapped in the heater core/ valve/ hoses

how's the condition of your oil? it's not milky? evidence of water mixing to your oil? pull dipstick, check under the oil cap or keep a note of it for the next oil change... heck, if your oil is dark from overheating more than once already, it's probably good to change the oil as well now:eek:

you can rent a pressure tester from a local autozone or similar & pump it up to 13-16 lbs, then verify if the pressure is holding or escaping out somewhere to help spot if there's a leak somewhere

that same pressure tester/rental also have an adaptor to check/ test your rad cap before buying a new one---------------------------

follow aleekat's advice first since you didn't say that you made sure there were no air bubbles trapped in your system after the coolant change/ flush

there's also a neat funnel to make burping the system from air bubbles if you can't do it the backyard-mechanic way:

http://revlimiter.net/blog/wp-content/uploads/2011/03/DSC_1249.jpg

see youtube vids on how this works

I bought a new cap today. It read 16lbs. I told the guy my van has a 15 lb cap on it and he said that will work. The original cap had gunk all over it. After I flushed the system I wiped some of that gunk off. But couldn't get it all. I didn't know that you're not supposed to open the bleeder screws while the motor is hot. GLAD you told me that. I won't do that again.
So I add antifreeze to the radiator then I start the cold engine and then open both bleeder screws and then add antifreeze until it comes out of them? Then close the screws.? Hope I got that right.
I drove it out to my dad's house and parked it on a steep hill opened both screws and the cap. (Didn't know I wasn't supposed to open bleeder screws while hot engine.) I added antifreeze and when I saw it coming out the bleeder screws I closed them. And when the radiator was full I put the new cap on. BUT I did notice the over flow tank had less in it then it did this morning. So I'm hoping it finally sucked some back out of the over flow tank when it needed it.
I drove the van home and only once the temp gauge went up to half way and got a little cold air for about 10 seconds the temp gauge went back down to little over 1/4 mark and stayed there and then had hot air again.
When I got home I looked at the engine to see if I could see any leaks anywhere and didn't. But the new radiator cap was really cold. Is that normal? I did see some action in the over flow tank like it was pushing or sucking it out of that. I've always felt the caps hot after the engine was up to temp.
I changed the oil right after I bought the van and I have checked it 3 or 4 times within 2 weeks to see if I could see any antifreeze in the oil and I haven't "YET" knock on wood. lol The full mark is at the same place when I filled it with oil. I couldn't smell any sweetness of antifreeze on the dip stick either. I had a heater core go on a car I have so I know what it smells like.
THANK YOU again for the info.
THANKS, Dan

I am going to napa and pick 1 of those kits up also.

When I did add the antifreeze today at my father's house I didn't add a lot.

Dan, sound like you have just about whipped it, Good luck.

I tried again last night to get air out and didn't work. I told a friend of mine that's a mechanic all the stuff is going on with the van. He said the head gasket is gone because the piston is pushing air up into the port. So looks like I'm doing a head gasket job. I've been reading a lot of stuff, so I what's in front of me. lol Had some1 email me some stuff also. I'll post some pics and let you know how its going. Thanks for everyone's help.
Dan

I tried again last night to get air out and didn't work. I told a friend of mine that's a mechanic all the stuff is going on with the van. He said the head gasket is gone because the piston is pushing air up into the port. So looks like I'm doing a head gasket job. I've been reading a lot of stuff, so I what's in front of me. lol Had some1 email me some stuff also. I'll post some pics and let you know how its going. Thanks for everyone's help.
Dan

Have you done the test for gases in the coolant??? I am not sure where you can get the testing stuff but I would assume parts stores should have it. I would test before tearing it down and not finding anything wrong. Just a thought.

DO you see any bubles in the overflow reservoir as it runs??

If it is a head gasket, the usual culprit is cyl #1........

Have you done the test for gases in the coolant??? I am not sure where you can get the testing stuff but I would assume parts stores should have it. I would test before tearing it down and not finding anything wrong. Just a thought.

DO you see any bubles in the overflow reservoir as it runs??



After reading a lot of problems with the head gasket problems I am going to replace it.

I don't want to have to worry about when it's going to let go.

I don't remember seeing air bubbles in the over flow tank.


The mechanic I know let me barrow his tool he made.
He told me to:
Open radiator cap.
Screw it in the cylinder and put about 100 psi in it.
If I see bubbles coming out of the radiator then it's that one.
Keep trying till I find it.
He said it's probably cylinder # 1. Just like what Tech said.
I'll get you posted.
Thanks, Dan

Could be a cracked head if you overheated it......