Over heating 1998 3.4

New to the borad..3 days ago Low coolant light came on the went back off, added a little coolant when I got home, next day started running a little hotter, Open radiator to check coolant seem to be full. ran fine until tonight .on way to friends house started running hot again luke warm air coming out of heater. Looked under van when I got to friends and there was coolant coming out around then oil pan in back, could not see where it was coming from.He open radiator and put in some Bars radiator stop leak to get me back home, Filled the radiator back up to full and it stopped the leaking but its still running hot at times Air from Heater is only luke warm.Gage go's up then it will come down, but air never get hot from heater. Any Ideas/ Sorry so long.

Sorry...classic 3.4 blown head gasket syndrome...tons of that stuff on this forum. Search for "head gasket"
Do not spend dollars on radiator and water pump and other non relevant items.
BLown gasket lets exhaust invade the cooling circuit so the heater has exhaust instead of coolant to pump heat...a very poor heat transfer medium.
AN improved gasket FROM GM is supposed to cure that very well known problem.
And..better to rinse radiator and get rid of that stop leak ASAP before it forces you to change the radiator too.

How hard is it to replace the head gasket? Can I bleed some of the air out of the system somehow? Its the only car I have at the moment.

It may only be an intake gasket, much more common problem and is what causes the head gaskets to go due to overheating from coolant loss. If you have sludge on the oil cap or in the pcv valve, milky oil, and if you can smell coolant under the hood, the intake is most likely the problem. Unless you have overheated it many times, or let it get really hot, the head gasket(s) may still be ok. A compression test will verify whether the head gasket has failed due to the intake problem. Fel-Pro makes a new intake set that includes an improved design intake gasket, plus the valve cover gaskets (part number MS98003T) that will permanently fix this known issue. The plastic OEM style gaskets are junk.

How hard is it to replace the head gasket? Can I bleed some of the air out of the system somehow? Its the only car I have at the moment.
With (a) blown head gasket(s), you have exhaust injected in the cooling system and even if it were just air squeezed in during the compression cycle, it will invade the cooling system on a continuous basis as soon as the engine runs. So the story of purging and extracting the air has been tried and tried again in similar circumstances to no avail.
...and while blown intake gasket will let coolant seep out of the engine and /or into the oil pan, it would have no effect on impairing the cooling system and the heater performance when radiator is seen as full..but anyway, on the way to head gaskets, you will have a meeting with the intake gasket first....so always time to make up your mind. Obviously I myself would like to stop right there.

Could it be a thermostat not opening all the way. I have luke warm air?

____

No water in oil, but I can't get anymore then luke warm are even when its running hot, And Its full of Coolant? Thats why I thought may a bad thermostat

No water in oil, but I can't get anymore then luke warm are even when its running hot, And Its full of Coolant? Thats why I thought may a bad thermostat
Redman,

I have seen numerous posts on the Chevy Venture, Pontiac Montana, & this forum with these symptoms, most with the 3.4 liter engine. I would bet $1 (I'm not a bettin' man :) ) you have a leaking head gasket. I assume that if you search all the GM forums, you would find similar results.

If you would like to experiment, you could try bleeding all the air out of the coolant passages (2 bleed nuts) and see if that works (heat comes back) for a day or two. If the symptoms come back (along with the air in the coolant system), that would probably confirm the leaking gasket.

I'm not an expert, but I have seen this type of post repeat several times since I have been here.

Please let us know what happens.

Take Care,

But why am I not getting heat from the heater. Its full of coolant and still the air's luke warm..I have only found 1 bleeder screw?Are there 2?

But why am I not getting heat from the heater. Its full of coolant and still the air's luke warm..I have only found 1 bleeder screw?Are there 2?

Because you get exhaust gases instead of coolant in the heater. As Exhast gases is a very pore heat transfer, you don´t get any heat from the heater.

But why am I not getting heat from the heater. Its full of coolant and still the air's luke warm..I have only found 1 bleeder screw?Are there 2?
Nicke66 mentioned why you may only be getting warm air instead of hot.

As for the bleeder screws, my manual says there is one on the thermostat housing and one above the coolant pump.

The point is: if you continue to get air in the system after it has been removed, you probably have a leak.

Take Care,

How about a hose somewhere on the back of the motor leaking? there quit a bit of coolant coming our from back there and I can't see where?are there hoses aback there?

Found out it's an intake gasket, How hard are they to replace?

Dealer takes one full day. It is very tight working under the hood. Had mine done about 20k ago under warrenty. EGR failed, pain in the but to change. I can only imagine doing the intake. I have 70k now. Horn starting to blow by itself. You just have to love it.

I suggest you read this thread just a few threads away...about "97 transport water in oil" . With the heater problem, intake gasket does not seem to fill the bill. Do not loose the opportunity to check for head gasket because doing the job twice would add insult to the pain. My trick is to position each piston so both valves are closed and apply air pressure through the spark plug hole using some device that ensures a tight fit so you can built up pressure inside the cylinder. A blown head gasket would let air seep through the cooling system and pop bubbles out of the radiator (fill up to the cap and have someone look while another applies pressure).

OK, For some reason this thing has been running fine. Not over heating at all??Do you still think its a Head or Manifold Gasket? You can still smell it once in a while like its leaking but haven't had to ad any water?

If it runs fine, I would not look for more problems: they just have the habit of coming by themselves. Just glad it works fine....

getting ready to take it on a trip and didn't want to have any problems, Have driven it over maybe 20 to 30 miles at a time,So I thought better fix it

..I had though from your March 28 post that the intake gasket had been changed......I just think I'd arrange to keep at safe proximity from home.....