Won't Burp!

[Superdave]

Ok.. so i seem to have this problem with every V6 Jbody/engine combination i've had.. the damn things just won't burp out all the air!


my 3500 overheats in like 5 minutes of running, the only changes to the cooling system are the lack of hard lines to the heater core (they're pinched shut and welded). I'm using the original '91 V6 radiator and a '93 V6 coolant reservor. It just seems like a never ending cycle of Start, run, coolant boils out of the top of the tank, tank goes empty, more water goes in, temp goes down.. temp goes back up and repeat....


I know a professional radiator flush with a pressureized system should take care of this but there are no shops close enough with the right equipment to do it.. i don't want to have to stop halfway through town and let the car cool off.. lol

for now i'm running 100% water untill i'm completely sure the LIM is OK. It's also helping to flush out tons of other gunk in the radiator


So my question, does anyone have any tricks or suggestions to get this thing to stay cool?


Thanks,
Dave

[CNCguy]

Doesn't the thermostat force the coolant through the heater core until warm up? IIRC the thermostat is long and has a section the covers the coolant bypass until it starts to warm up some. If so, perhaps the coolant never gets a chance to circulate and the hot coolant never reaches the thermostat to make it to open. Maybe you could drill a small (.093) diameter hole in the thermostat to enable a small amout of flow and also get rid of any trapped air.

Whatever it is... just get it fixed. I have been anxiously waiting to hear how it runs.

[93ztwo4]

i am having the same problems with my 3500 but i just dont have those lines anymore i plugged them up.

[IsaacHayes]

Yeah I would make sure the coolant can flow between the heater core or at least stick a rubber hose so it flows like normal. That would probably be one possibility to fix before you go looking for other things.

I've always gotten mine burped but it takes a lot of idling and getting the car hot and revving to get the bubbles out. Yours spilling out sounds like it's got other issues and I'd say it's cause you dont have flow where you should through the heater core.

[PCGUY112887]

Just curious, why are you so worried about the LIM?

[treeZ24]

on the 3400's you take off the hose from the waterpump housing pipe to the LIM bypass, then fill the rad overflow, its the highest point.

[Superdave]

Just curious, why are you so worried about the LIM?

It's a 60degreeV6..

I've had too many LIM gaskets fail in other cars, even a few SBC's so for added insurance i run water for the first hundred miles or so. I'm taking no chances with this engine, if it blows the car is getting pushed into the Mississippi river.

[IsaacHayes]

I got dibs on the car, or heck the top end of the motor and UDP! lol

[Superdave]

well, after an hour today it's still not burped. For a while the cooling fan wasnt coming on but it is now...

i fired up freescan and the CTS for the ECU (rear head) is reading 88-100c the fan is set to turn on at 100c (212F) but at the same time the sensor in the front head is reading 260+ F

The sensor in the rear head is the stock 3500 one, front is from a LS1 but they have the same p/n...

I unhooked the line that runs from the water neck to the bottle, ran 2 long hoses from the bottle and the line into a bucket.. then used my garden hose to pressurize the system. It burped out a bunch of air but the little shit is still overheating!


So i guess next is to pull the thermostat and drill a hole.. I bet that's where the air pocket is, right behind it.

[93ztwo4]

^ i am also using a 3500 sencer but only oe of them and my fan will not come on. i think maybe th problem might be the thermostat

[Superdave]

^ i am also using a 3500 sencer but only oe of them and my fan will not come on. i think maybe th problem might be the thermostat

so you have the gauge and computer running on the same sensor?

from what i've read that won't work.. is your gauge reading ok?

[IsaacHayes]

I still think you should of allowed coolant to flow through the heater core pipes, even if you don't have a heater core. You changed the operation of the stock cooling system and that has to have some affect on things..... I would of at least connected the two with some rubber hose and 2 clamps. Hell less work than welding them shut :P

I would think that perhaps thats why one head is hotter, and coolant is being forced out of the over flow bottle. I know on old classic cars you could shut off the heater core flow with no affects (to stay cooler inside the car in summer) but I'm not sure how they routed the cooling vs the 3500.

[Superdave]

I still think you should of allowed coolant to flow through the heater core pipes, even if you don't have a heater core. You changed the operation of the stock cooling system and that has to have some affect on things..... I would of at least connected the two with some rubber hose and 2 clamps. Hell less work than welding them shut :P

I would think that perhaps thats why one head is hotter, and coolant is being forced out of the over flow bottle. I know on old classic cars you could shut off the heater core flow with no affects (to stay cooler inside the car in summer) but I'm not sure how they routed the cooling vs the 3500.

Now that i did this drawing i can see where the problem is. You are correct, it appears that i need the coolant flow through the heater core lines to get the air out from behind the thermostat. I'll see if i can come up with something this weekend...

http://www.3500z.com/Misc/cooling-system.jpg

[CNCguy]

Now that i did this drawing i can see where the problem is. You are correct, it appears that i need the coolant flow through the heater core lines to get the air out from behind the thermostat. I'll see if i can come up with something this weekend...

http://www.3500z.com/Misc/cooling-system.jpg

Dave... You could get a different thermostat that doesn't block the coolant bypass. That would allow the coolant to circulate through the block and back to the water pump until the engine is warmed up. The new thermostat just needs to be the correct diameter and proper temp. As you can see in the pics, the stock t-stat has a section on the back that blocks the coolant bypass to force the coolant through the heater core. Just match up a t-stat without that section. And as I said before, a tiny hole will help with getting trapped air out.

[93ztwo4]

so you have the gauge and computer running on the same sensor?

from what i've read that won't work.. is your gauge reading ok?

i dont have the gauge hooked up i have an autometer temp. but that shouldnt affect anything.