More overheating

[ejazz]

Guys-
I know there is a lot of bad intake and head gaskets with the Venture vans and my brothers is no different. His van ('99 3.4) only occasionally over heats. If I bleed all the air out of it, it will run fine for a while. Then the temp gauge will start bouncing around and the heater doesn't blow any heat. It seems like an air pocket is definetly moving around. My question is this: Has any one else expierenced this and I'm hoping it's just the intake gasket pushing air into the cooling system and not the head gaskets. There is no coolent in the oil and it doesn't seem that it is burning any. Thanks

[gunjes]

I have had the same problem, 99' 3.4L van would sit a idle just fine and then when I took it out on the road. temp gauge would bounce from overheating to normal. heater would be stone cold when overheating and when temp. gauge would fall back to normal limits; heat would come back to system. I then noticed that the resevior was filled to overflowing capacity, when I returned home and popped the hood. I also continued to try and purge any air out of system( as I thought it was a air pocket:due to heater core replacment). I did notice a different amount of vapor from the tailpipe during idleing, but not during road driving( which would indicate a bad head gasket)nothing in oil either. My mind was twisting at this point( I checked the water pump, replaced the raditor cap and checked the termostat; none of this helped). Finally took it to a friend that tested the coolant for exhaust; nothing. He then used a tool that allows you to presurize the coolant system( fits on top of the raditor) and pumped it up and watched the gauge, it slowly dropped indicating a leak. It has to be the lower intake manifold gaskets , which are notorious for failure. There is no visible leaking on motor or under van. Since i had just replaced the heater core and wanted to make sure that it was not leaking, I had not put everything back together( so it is not leaking either). This what I have summized and hope this will help you

[ejazz]

I have the same situation going on that you describe, but I just spent 7 hours changing the intake gaskets, thermostat, and radiator cap. The way it is acting doesn't seem like a head gasket. At idle it will run fine (temp) with decent heat coming out of the vents but once going down the road the temp gauge skyrockets into hot and no heat comes out. You can pull over for a second and crack the bleeder open by the water pump, release some air/steam, and the temp will drop into the normal but still no heat in the cab. After doing this you can drive again and the temp gauge will go from cold to middle of the range with no more overheating but still no heat in the cab. With my experience with blown head gaskets, wouldn't it heat up and stay that way? It almost seems like their is no circulation at higher speeds? Maybe impellor slipping on waterpump? I don't understand why with the temp gauge in the middle of the range I don't have heat. There must be an air pocket in the heater core? Are these 3.4's just that hard to bleed the air out of? When I first changed the intake and bled the system, the van ran fine with excellent heat for the first 20 miles, then this stuff started happening again. I'm stumped and this Venture is down the road when this is fixed!

[gunjes]

Yea, I have that same thing, but i haven't done the lower intake gaskets yet. Wow, this is really disheartening to learn that the lower intakes may not be the problem. I also thought of the water pump impeller and removed the water pump to check it for errosion and slippage( it was intacted with no slippage). But please check yours as this may be a problem to your vehicle. gasket was only two dollars. AS far as the heater core with an air pocket in it , I also thought of that. So I waited till the engine was cool and then took off the rubber house from the water pump bypass line( still connected to return line off heater core) attached a funnel and cracked the bleeder valves. Then tried to fill the heater core this way. trying to out smart the thermostat and the enginners. Could put a little in at a time but would eventually fill up. Reconnected everything and began the whole air bleeding saga again. Nothing, just the same temp gauge conditions and hot air/steam from the bleeder valves also. I have done this whole air bleed stuff four days and countless hours. I even tried using my air compressor( set the regulator a 15psi) and presurized the system through the coolant overflow line, with the coolant system filled as much as it could hold. cracked the bleeders slowly and waited for coolant. Thought I had it fixed and nothing just the same thing again. I know this might seem a bit confusing and I apoligize in advance, but I am also looking for a resolution to this problem.

[ejazz]

Guys,
I pulled the heads off my brothers '99 this weekend and dropped them off at the machine shop to get checked. The owner of the shop said he sees 3.4's now and then, and usually the heads are cracked. Hopefully mine aren't! I'll let you know what happens after I get them back on.

[jwheels]

Hello ejazz,
I am new to the site. I wish I had been a couple of days early. Change the rubber O-rings in the coolant pipes. There are four. Did you notice if your hoses were collasping with the engine running. If they are over four years old change them. Once everything is back together, do a pressure test on the coolant system. You should be able to rent the tool from the auto part store. I hope you get it running!
jwheels

[gunjes]

yea, my friend also told me about the poor quality of the heads and advised me to remove them and have them( I believe) magna honded, or something to that nature. Any idea on replacment prices?

[jwheels]

See if the machine shop will give you a price on rebuilding your heads. They should let you know if they can be restored.

[ejazz]

Guys,
I picked up the heads this weekend and got the van back together with great results. The rear head gasket (closest to the firewall) had a slight seepage leak that would only leak when hot. We had it back together in about 5 hours. I replaced all the o-rings on the coolent pipes, the plugs, and the oxygen sensor while I could get to it. The machine shop checked the heads for cracks and put new valve seals in. The total for the labor and a head set from Clevite with all the gaskets, o-rings, and seals was $280. Not bad. After getting familiar with the van from trying the intake gasket first, it's really not that hard to do. I have done this on several other vans and it's basically the same procedure except GM designs some of the dumbest brackets and parts I've ever seen. You have to take off five brackets to get to the one bolt you want and they have so many nooks and crannys that you can't reach into. I'm missing three sockets after the project! Get a good flexible magnet! I hope this info helps and feel free to ask if you need help.

[gunjes]

I'm really glad it worked out for you. These "o-rings", where are they? Thanks in advance

[ejazz]

The o-rings are on the coolent pipes where they slide into the intake manifold. There is also one on the bypass pipe where it goes into the top of the water pump.

[djphix]

ejazz,

I'm trying to get to my head gaskets, but I can't get the passenger side front motor mount off. I've found 4 bolts that appear to hold it in place (one short one that mounts into the head up top, one short one that fastens into the block, two long ones that are down by the a/c compressor that mount into the block). Can you tell me which one I might be missing?

Like you, I already replaced my upper and lower intake manifold gaskets to no avail. Originally, my problem occurred once on a cold Friday. It warmed up for the weekend and the van drove normally. The next cool down brought the problem back for good. I was getting coolant in the oil pan, but I haven't since replacing the intake gaskets (the van's only seen about 50 miles since then). The head gaskets seem to be a logical solution now.

I'm just glad I have alternate transportation. The first shop I took it to quoted me $1800 to do the head gaskets.

Thanks,
phix

[Ihatemyventure2]

I have the same damn problem can't get that torque strut bracket on the passenger side off!

[djphix]

Originally Posted by Ihatemyventure2

I have the same damn problem can't get that torque strut bracket on the passenger side off!

I decided to sacrifice the front left bolt in the head. It has a shoulder that extends beyond the hex that acts almost as a dowel pin through the torque strut bracket. I drilled a hole (about 10mm) down the middle of the shoulder. Once that was done, it was pretty easy to wiggle the left torque strut bracket off. I'm figuring I'll buy another bolt when I go to buy the gasket. I'd imagine you could get a similar result by heating the bracket, but I'm not sure it's wise considering the state of the fuel lines.

After you get the torque strut bracket off, DRENCH the studs holding the exhaust manifold on with liquid wrench. The two left (front) studs both broke off in the head on me.

[Ihatemyventure2]

Originally Posted by djphix

I decided to sacrifice the front left bolt in the head. It has a shoulder that extends beyond the hex that acts almost as a dowel pin through the torque strut bracket. I drilled a hole (about 10mm) down the middle of the shoulder. Once that was done, it was pretty easy to wiggle the left torque strut bracket off. I'm figuring I'll buy another bolt when I go to buy the gasket. I'd imagine you could get a similar result by heating the bracket, but I'm not sure it's wise considering the state of the fuel lines.

After you get the torque strut bracket off, DRENCH the studs holding the exhaust manifold on with liquid wrench. The two left (front) studs both broke off in the head on me.

Thanks for the info! I was wondering if that thing was holding it on there. Your right it almost loooks like a dowel pin, and I didn't realize it was even part of a head bolt. By the way if it is a part of the head bolt I wouldn't worry about it to much because you are suppose to replace all the head bolts when you do the gaskets because the threads are stretched.

Quick question! For sure for sure how many bolts were holding the strut bracket in place other then the one that looks like a dowel? GM dealer said only two, which was all I could find!