[TomasJohansson]

Hey guys,

I just replaced all the coolant in my Z6 and after a big hassle to get the pipe back in to the water pump and filling up not as much coolant as the service manual states, the vehicle will quickly get too hot during idle. Thermoswitch on radiator and fan seems to be functional, I've shorted the switch and the fan kicks in, but not when the temperature rises. However, the radiator will not get hot at all, it seems that no coolant gets around to the cylinder. 

I did flush the system with three runs of fresh, cold water. I was not able to fill with the specified 2750 cc however, more like 1900, 2000 cc. Would this be an indication of any issue?

I think I have bled the system from air, by opening up the "other" screw on the water pump. I did get a solid burst of the new coolant liquid, after some hissing noises. Are there any other things I can do to remove any air pockets?

If I squeeze the rubber inlet pipe right next to the pump, I can hear and feel liquid in there. I cannot not feel or hear anything on the rubber pipes that goes to the thermostat and back on the other side from the cylinder.

If I remove the radiator cap, and start the engine, I can see the coolant level rising up that pipe. I would hope that this would be an indication that the water pump itself is ok and that I have coolant pressure? Is running with the cap off beneficial to bleed out air?

If I have the radiator cap on while idling, I cannot see that any coolant enters the expansion reservoir. Would this be an indication that the cap is kaputt?

Finally, I did yank out the thermostat. I was kinda waiting for a burst of coolant when I opened up the thermostat cap, but that area was not as wet as I thought. Nor was the thermostat when I pulled it out. I put it in hot water, and got some "result" from it, but I am not qualified to determine if it is ok or not. Unless I get some other ideas from you guys, I will get a new one.

Let's see if I have any additional clues for you: I have found that the expansion reservoir is almost always empty when I check the levels, but I do not have any issues with apparent leaks. The hose between the radiator cap pipe and the reservoir is not clogged. After I had filled up as much new coolant as I could, I filled up the reservoir to the "low" level, and after some other experimenting during idle and stopped, that level have dropped significantly.

Sorry for a long post, but thats how we swedish people are :-). Any suggestions would be greatly appreciated!

/Tomas

[REDRIDER]

sounds like air pockets in the engine. somehow you have to get that air bleed out. sometimes lifting the front of vehicles high in the air helps and makes the radiator the highest point. I am not familiar with these cooling systems in particular though. That is what I would try first and run it with the cap off until the thermostat opens and you get warm water running through the radiator then top it and cap it. of course if the engine is air bound you wont get the thermostat to open as it needs coolant to be touching it to heat the element to open. This is probably why you got some results when you filled it through the thermostat when you removed it.

[TomasJohansson]

Thanks. I've replaced the thermostat, but that does not do it, it still overheats and I get not warm liquid flowing to the radiator.

All that happens is that the level in the expansion reservoir is dropping a bit, so I can top that up, but the amount is not much. I am waiting for the cylinder to cool down now, and will run without a the thermostat to see what happens.

Looks like I am going to tear apart the water pump tomorrow....

/Tomas

[NMKawierider]

You need to know that if by chance the mechanical seal has been run without coolant ..as in the water pump has a trapped air pocket in it, that seal will toast itself in very little run-time. So if coolant starts coming out the weep you will know why.

Seems I remember reading somewhere about a process of purging air out of a CFM engine that involved the removal of some bolt or plug at the top of a cylinder...or somewhere close to the thermostat while filling. Can't remember what engine it was...I didn't do that with my 800 when I changed it but I did jack the front up as high as I could while filling slowly.

[TomasJohansson]

Thanks, you were on to something there. I've managed to get it working! I removed the brand new thermostat, and put my finger in there. It was not dry as a desert, but it didn't have any signs of the new coolant. So I topped up the reservoir again, and squeezed on the water inlet tube while the thermostat housing was open. And sure enough, after a few gurgling squeezes, the new coolant started to drip out from the cylinder head. Put the thermostat back on, topped up the reservoir, fired her up, and a minute later, I had warm coolant in the radiator.

I'll keep my eyes open for any signs of a toasted seal.

/Tomas

[REDRIDER]

Thanks. I've replaced the thermostat, but that does not do it, it still overheats and I get not warm liquid flowing to the radiator.

All that happens is that the level in the expansion reservoir is dropping a bit, so I can top that up, but the amount is not much. I am waiting for the cylinder to cool down now, and will run without a the thermostat to see what happens.

Looks like I am going to tear apart the water pump tomorrow....

/Tomas

Did you try jacking up the front as high as you can?

[TomasJohansson]

Hi,
I do not have that kind of jacking capabilities, I can barely get the wheels off the ground. I could put it in a ditch with the front up high however, I'll try that and see if I can get any additional air out. I did get a flow to the radiator by manually squeezing the inlet pipe with the thermostat housing removed.

/tomas

[REDRIDER]

any luck?

[TomasJohansson]

Oh, sorry :-). Yes. I had to remove the new thermostat and squeeze on the rubber inlet pipe, the one that feeds the water pump from the radiator. This pushed the coolant up to the thermostat housing, and when I then put the thermostat back in its housing, it was in contact with the liquid. Fired her up and as far as I can tell, the thermostat then opened up as it should, and I got coolant flowing in the system again. When the thermostat was in an air bubble, I had no flow and the engine came close to over heating.

Next time, I will have the front end high up in the air when I fill up the new coolant.

Thanks everyone!

/tomas

[LaserGuy]

Sometimes it can also sneak up on you. When I bought my machine, the dealer charged me for PDI, but NEVER did it, and just pocketed the money. One of the deficiencies was a empty overflow tank, so I filled it up to the line, and had no problems at all for 400 klm of running, then all of a sudden it over heated. At first I thought it was the temp switch on the rad, but tested it and ruled that out, removed the thermostat several times took off the rad cap, and squeezed the rubber hose, Air bubbles came out of the rad, and finally I had circulation again and topped the tank back up. Ran it until the temp gauge came up to the start of the 4th section, the fan came on and it went back down. All has been fine for the last 200 klm. There must have been air in the system someplace that did not affect the temp for 400 klm and then it seemed to bubble into the wrong place and cause headaches. Now I keep a very close eye on it, and obviously I stay the hell away from the dealer that sold me this machine..

[REDRIDER]

Sometimes it can also sneak up on you. When I bought my machine, the dealer charged me for PDI, but NEVER did it, and just pocketed the money. One of the deficiencies was a empty overflow tank, so I filled it up to the line, and had no problems at all for 400 klm of running, then all of a sudden it over heated. At first I thought it was the temp switch on the rad, but tested it and ruled that out, removed the thermostat several times took off the rad cap, and squeezed the rubber hose, Air bubbles came out of the rad, and finally I had circulation again and topped the tank back up. Ran it until the temp gauge came up to the start of the 4th section, the fan came on and it went back down. All has been fine for the last 200 klm. There must have been air in the system someplace that did not affect the temp for 400 klm and then it seemed to bubble into the wrong place and cause headaches. Now I keep a very close eye on it, and obviously I stay the hell away from the dealer that sold me this machine..

yup likely got behind the thermostat and didn't allow it to open. The element on the thermostat only reacts with fluid to open, hot air doesn't cut it.