Overheated. Replaced thermostat - how to bleed (GXP)

[rwebb616]

Hi,

I was tooling down the highway when I got a check gauges indication in the HUD - look down and temp is at about 240 or so... slow down and pull off the road and shut it down. DIC now displays "A/C Disabled" and "Engine Hot - Idle Engine". I open the hood and can't really tell what's going on - doesn't look like coolant anywhere - water still in the tank from what I can see. 3/4 mile from the next exit and nervous as hell being in front of my car along side the highway. Lower the hood and get back in and let it set for about 5 minutes. Turn the key back on and the temp has dropped a bit. Fire it back up and head for the exit. Got off and within sight distance is an auto parts store. Decide to go for it. Temp now is back at 240. I pull into the parking lot and I have an indication on the DIC saying "Engine Hot - Shutdown Engine" and so I do - temp now just into the red bar at the far right. I call and talk to my mechanic and he suspects thermostat stuck so I buy a thermostat with plans to replace after work.

I replace the thermostat, fill the tank, and fire it up with the cap off - cold air at the vents put it on high. Let it run up to 240 - still cold air at the vents. Shut it down and let it cool back down to 200. Started it again... all the while checking the tank - level not going down much (it did one time and I missed it - could have sucked some air) again no warm air - got up to 240 again. At last check the tank level still had not moved. Total I had dumped about a half gallon of 50/50 coolant in there. This time I decided to shut it down and leave in the parking lot for the night.

My question is this - could this still be an air pocket or am I possibly looking at a head gasket? It got all the way to the right (not pegged) once and from what I could tell did not enter limp mode unless it did it right as I was shutting it down. Fans only ran for maybe a minute or so after shutting it down before they turned off. It did throw a code but appears to have cleared. I didn't have a scan tool to pull the code.

Looking for advice.. How long does it take to bleed? I understand that the N* auto bleeds and there is no bleeder screw anywhere.

Thanks
Rich

[sethjamesrimrodt]

Is your water pump turning? It's on the drivers side front valve cover.

[rwebb616]

I'm not by the car right now.. is that belt driven somewhere? I thought the main serpentine was on the passenger side? Thats where I suspected the water pump was. I'm not hearing any squealing from a belt or anything. I'll have to look for that when I get back at it. Right now the car is probably buried in about 1.5 feet of snow as it got to spend last night in the parking lot!

If it IS the water pump is that a hard fix?

[dpnewfie]

The waterpump has a belt of its own. You may have lost that belt or the idler pulley.

[rwebb616]

Okay thanks - I'll check that when I get back to it sometime today.

-Rich

[dpnewfie]

If it is what I suggested than it is easy to replce. The waterpump on the other hand is a completely different story.

[rwebb616]

If it's the water pump wouldn't I have a leak or something there?

Rich

[dpnewfie]

Most likely. That's why I suspect the belt or idler pulley.

[rwebb616]

You da man! That's exactly what it is. The belt is freyed into about 5 strands. I didn't notice it because of that metal belt guard shield covering it. Now onto how difficult is it to fix that? Have you changed one or can someone chime in?

-Rich

[dpnewfie]

Quite easy actually. Remove the bolts/nuts holding the pulley guard in place. Then remove the two bolts holding the idler pulley in place. Removing the idler assembly is the easiest way to do it. However, you can get the belt off without doing this; it just takes a little twisting and yelling. lol

Oh, and I had a idler pulley go out on me. These are cheap and might be a good idea to replace yours now that you have to remove it anyway. Just my two cents there of course.

[rwebb616]

Got it changed and all is well! Thanks for the suggestion - didn't even know the water pump wasn't part of the main serpentine belt.

-Rich

[dpnewfie]

Good stuff, Rich!

[rwebb616]

Great... just found out that my thermostat replacement job wasn't good enough... it's leaking. I tore it all apart tonight and thought I was being extremely careful to get things to seal. Put it all back together and added some coolant and put my hand around the bottom of the thermo housing and it's dripping... not even under pressure.

Any ideas? What seems weird to me is that the thermostat doesn't seem to fit the cavity correctly either... I have to depress the spring about an eighth of an inch for it to go all the way in - is that right? All it came with is a little rubber o-ring that seems to fit the channel but was nowhere near as thick as the one I took off. I asked the parts guy about it and he said they get that way after being in there for a while.

The kicker is that I probably didn't even have anything wrong with my thermostat and I went and changed that first. Didn't even know about that belt on the other side.

What to do...
-Rich

[sethjamesrimrodt]

I'm still saying water pump, they leak out of a weep hole when the bearings go bad and they will shred a belt. Mine shredded a belt, had a bad tensioner bearing, and a bad water pump within a month.

[rwebb616]

What about the thermostat not seeming to fit the cavity? Should I have to depress the spring when installing it? Or should it go far enough in that it sits flush?

My car has 71,000 on it now and I think it's the original pump - probably not a bad idea to replace it anyway since I am going to have it just about all the way apart anyway. I just need to find a parts store somewhere local that I can rent the tool from to take it out.

-Rich

[sethjamesrimrodt]

Mine sat flush I'm almost sure of it. My water pump went out with less miles then that. It was still spinning freely but the seals were out of it.

I had to buy the tool from NAPA it wasn't too much money. Even with the tool it's a pain in the ass if you ask me.

[CMNTMXR57]

Most thermostats with the rubber O-ring will sit flush. Then the top portion of the housing that fits over it, seals with the rubber O-ring. So if it isn't sitting flush, somthing isn't right. Sounds like it's too long and hitting something on the inside of the housing.

With the pulley being plastic, I was actually more concerned with breaking it when I applied the forces needed to pop it loose.

[rwebb616]

Okay I'm an idiot.... I didn't realize that there was a slot in the o-ring to go around the thermostat.. works much better. I'm replacing the pump as well now but not a bad idea for sure at 71,000.

Is it necessary to do an extreme cleanup job on the place that the water pump oring comes out? I dried it all off with paper towel but do I need to do much more with that?

-Rich

[CMNTMXR57]

I usually get the dremel out with the wire wheel and clean up all those surfaces. Just be sure to block off the hole it's in with a towel/paper rag/etc so that none of the junk you buzz off gets into the hole.

[rwebb616]

Thanks for the suggestion - and it is a good suggestion, however it's all back together now. I just cleaned it best I could with the paper towel and bought a new o-ring for the housing and it doesn't appear to be leaking (although it is seemingly low on coolant the last three times I checked - just attributed that to air pockets)

-Rich