Steve_Jones said:You keep saying "burp it". I just want to make sure you are using the bleeder screw and not burping it through the thermostat itself like an old school muscle car. I am also assuming it's the 3.6?
Yes, 3.6. I wait for it to cool enough that there is no pressure under the cap. Remove the cap, open the bleed screw until it dribbles, refill radiator and close. Rinse and repeat.
I am using the bleed screw on the thermostat housing, though. Any chance they have another somewhere?
I'm pretty sure that's the only one, just wanted to check you knew it was there. If it's dribbling as you refill, I'd say 98% of the air is out from that alone, and that's not your problem. Maybe crack it open, start the van, refill as it's running, see if that helps. I'm grasping at straws though, but might be worth doing.
E36 M3 like this is annoying isn't it? It should be fixed, but it's not.
Had the same problem on my subaru, actually did head gaskets because every suby needs to have them replaced. Well after that and a new radiator I pulled the motor and put another one in. During the teardown of the "bad" motor when I pulled the water pump the impeller FELL OFF the shaft. It was a stamped steel blade and the crimp to the shaft let go.
Okay, so another dozen burps since the last post. Passenger side up in the air to get air moving towards the bleed screw. I got it to where I was only adding the same amount it was burping into the overflow and still it would heat up enough for the computer to turn the radiator fan on and the radiator hoses were still ambient, ambient as in cooler than my hand.
I really did not want to modify the cooling system, but I was not getting the warm fuzzies about not being stranded at an autoparts store on a road trip, since bleeding was not fixing the problem. I went down the path of looking at all the ways that this system is different from every other system that I have worked on and I decided I did not like this system.
All of the older thermostats I have used are metal on metal, with a little hole. These do not hold pressure by design. The Caravan thermostat seals with a rubber gasket and has no vent hole. There is no path from the hot side of the closed thermostat to the cold side, except backwards through the running water pump. My original housing likely did not seal as well as the shiny replacement one that went in at last parts cannon. The bleed vent pulls air from the hot side of the thermostat only, for reference. That means that the thermostat has to open against the spring pressure plus the waterpump pressure and was being held closed by the waterpump pressure. Also of note, since the radiator was full, and the bubbles were on the block side, expansion in the system would force cold coolant in the radiator into the overflow, while air was still in the block.
I pulled the vent screw, and drilled a 1/16" hole under it, making a path from hot to cold. Now water pump pressure does not hold the thermostat closed, and it opens just when it should. Now, the system can take the air bubble that the thermostat was in and blow the bubble into the upper radiator hose, where expansion then pushes the bubble into the overflow instead of pushing the coolant into the overflow. Now the system is bleeding air out all by itself, just like every other bottom up cooling system since long before I was born.
I am not sure what obscure emissions driven requirement I just violated with a 1/16" hole, but now a collection of new parts won't leave me still stranded on the side of the road. We can also go back to putting low grade gas into the van rathern than putting premium into the 2007 Tahoe.
Except that one of the brand new parts I put in (waterpump, tensioner, or idler pulley) has a noisy bearing. I am not sure, if I were a kid now, that I would enjoy working on cars as much as when I was first learning. This whole thing of buying name brand parts and still getting junk out of the box would suck even worse if it were the only thing I had ever known. Stethoscope on order...
matthewmcl said:Steve_Jones said:You keep saying "burp it". I just want to make sure you are using the bleeder screw and not burping it through the thermostat itself like an old school muscle car. I am also assuming it's the 3.6?
Yes, 3.6. I wait for it to cool enough that there is no pressure under the cap. Remove the cap, open the bleed screw until it dribbles, refill radiator and close. Rinse and repeat.
I am using the bleed screw on the thermostat housing, though. Any chance they have another somewhere?
Open the bleeder with the engine off but hot and under pressure. That is the only way to get the air out.
In reply to Pete. (l33t FS) :
I had tried that once, but did not want to blow steam, so I switched to colder when I shouldn't have. As you say, though, that would have worked much better than what I was doing. Ah well, if the little hole causes a problem, I still have the original un-drilled housing to swap back in.
Edit: Thinking about it, I bled it hot tonight, just to check to see it was different, and I did not get any exta coolant (beyond the normal amount going into the overflow). I think I have had it pretty well bled for at least a couple days now, but I was still running into the problem of not being able to open the thermostat. After drilling the little hole, I had warmth in the hoses almost immediately. At the same time, I do not understand why, even if I shut it down and restarted "hot" that everything did not work. Perhaps the last hot start was done when I still had a bubble and every time since, I never had it quite warm enough. It could also be that the last truly hot start had a failing cap. So many details to isolate, but at least it is working, now.
If it works, it works!
A 1/16" hole shouldn't hurt a damn thing. A lot of engines have something like that designed in specifically to allow air out of high spots.
I am glad you were able to get it fixed!
On another note, Honda thermostats have a small hole like that in them and a little shaker that prevents air being trapped in the hole.
After a thermostat replacement, my Jetta is fun to bleed the air from. I am drilling a hole in the next thermostat the Jetta gets.
I drill a 1/16" hole in all of the thermostats I install. To heck with all those engineers. 
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