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LowSL2
01-19-2007, 07:51 AM
For the last couple of days I've noticed the temperature gauge doing some wierd things. Usually right after I start driving the car when the engine is cold. I'll see the temp gauge go up pretty quickly to the Hot side. Then as I start driving it'll go back to the Cold side. Then as I drive it would be fine.

But tonight after work it was 40ºF out, I let the engine idle for 5 minutes before I started driving. I usually wait until I feel hot air coming from the heater. But I didn't feel like waiting any longer so I got on my way. I got right onto the freeway and noticed the gauge doing it's wierd little thing again. But no heat coming from the vents. Then the gauge went all the way to Hot and I got the Check Gages light. So I got off the gas and the gauge wen't back down. All during this time theres still no hot air from the vents.

During my 20 minute drive home heat would come and go from the vents. Which is totally wierd.

So I get off at my exit and come to a stop light. The gauge keeps going up to Hot. So I turn the heater to full blast. Still no heat. I accelerate through the intersection and all of a sudden I get some heat and the gauge goes to Cold.

So I blast through all the lights and go to a gas station. I pop the hood and to my amazement, the engine is cool, the radiator is cold as well as all the hoses and lines. So I pop the cap to check to see if there's coolant in the radiator and coolant flies everywhere.

So I filled it back up with water. Started the engine and it had hot air coming from the vents. I didn't feel like doing any more diagnosis this late at night so I just put the cap back on, closed the hood and came home.

So... anyone have any clue as to what's going on? My first assumption would be that there's air in the cooling system. Then I started thinking that maybe the thermostat was bad. Or the water pump. I'm thinking of just replacing everything and flushing the radiator since it all seems to have 150K on it.

Thoughts? Ideas? Rants? Thanks

--Jeff Silva
DifferentRacing.com
1992 Dodge Spirit R/T
1992 Saturn SL2
1991 Saturn SL2 Drag car 11.8 @ 116

Tony Hanna
01-19-2007, 11:17 AM
From my experience you're first assumption would be right. My old Daytona was an absolute pain when it came to getting all the air out of the cooling system. I'd have to idle it with the cap off for almost an hour adding coolant as the air made it's way out. Even with a bleed hole drilled in the thermostat it was bad. As long as there was any air in the system, the temp gauge and heater would act exactly like you described. Once all the air was out it was fine though. The radiator would be full to the top of the neck anytime I took the cap off and the heater and temp gauge would act normal. It had me to the point where I hated having to drain the cooling system for any reason knowing I'd have to go through that when I filled it back up. For some reason the Sundance I have now is the exact opposite. It's never taken more than a few minutes to get the air out.
The important thing to consider is how the air got in there in the first place. If this becomes a reoccuring problem, I'd definately run it by a radiator shop. They can pressure test the system to check for leaks. Also, they have a tester that can tell if you have a blown headgasket or cracked head leaking compression to the cooling system. Hopefully that isn't the case, but I've seen it happen.

BIGBRUDDA
01-19-2007, 12:12 PM
Check for vacuum leaks in the heater control system. Split or melted 1/8 in tubing under the hood,or the connector pulled loose from the heater control in the dash.;)
Check the heater by-pass(4 way) valve for correct operation(bypass when the slider is all the way to the left). It's located under the battery tray. And does get "stuck".The metal arm should swing 90deg.
Also test the diaphragm-check valve that supplies vacuum to the heater sys. It's located on the Brake booster fitting. It should be about the size of a pill bottle, and only pass pressure or vacuum one way .It's designed to act as a reseviour to smooth out abrubt vacuum fluctuations. High boost, and age will rupture these.
The sudden initial temperature rise can be due to an old(sticky) thermostat.If you install a new one drill the vent hole out to 1/8 in. This allows for more bleed thru while the stat is closed, resulting in a more gradual rise.:thumb:

Frank
01-19-2007, 12:54 PM
I dont think the R/T's or any vehicle 90 and up have that heater bypass valve. I think you need to do a pressure check on the coolant. You are definently getting low hence eratic behavior and the results you see. The question is why is it getting low. How often are you replenishing your fluid?


Frank

turbovanman²
01-19-2007, 01:54 PM
10:1 you have a head gasket issue, its pressurizing the cooling system giving you air pockets and intermittant heat. That or the head could be cracked letting air get pulled in.

LowSL2
01-19-2007, 05:49 PM
The head gasket was replaced less than 1200 miles ago. But I'm not ruling that out. I think the place that did the work for the previous owner didn't fill the cooling system correctly. I'll have to play around with it some more I guess.

--Jeff Silva
DifferentRacing.com
1992 Dodge Spirit R/T
1992 Saturn SL2
1991 Saturn SL2 Drag car 11.8 @ 116
Edit/Delete Message

LowSL2
01-20-2007, 06:41 AM
Even more wierdness...

Did the wierd little thing with the gauge again tonight. But this time I had my OTC 4000e scanner hooked up and I was monitoring the coolant temp sensor. When the gauge would start to spike I noticed that coolant temp would go from 177 to 192. Then it went back down. At the same time I noticed a white cloud behind me. I thought it was coming from the exhaust. So I pulled over and popped the hood and there was coolant everywhere. It looks like it originated from the radiator cap/recovery tank area. But what was real wierd is the cooling fan was on and the engine was cool to the touch.

And another thing I noticed on the scan tool. It shows Charge Air at 32º constantly. Is that the sensor in the intake manifold?

I'm going to go ram my head into the wall some more...

--Jeff Silva
DifferentRacing.com
1992 Dodge Spirit R/T
1992 Saturn SL2
1991 Saturn SL2 Drag car 11.8 @ 116

turbovanman²
01-20-2007, 02:29 PM
Head gasket or cracked head, :(

LowSL2
01-20-2007, 04:47 PM
Will I be ablet o diagnose this with a pressure tester?

turbovanman²
01-20-2007, 06:22 PM
Will I be ablet o diagnose this with a pressure tester?


Possibly, if the head gasket is bad enough, you can pressurize it and let it sit overnight, pull the plugs and look down them. If you see coolant, you've found your issue.

What you can do is remove the thermostat, if you still have issues, then the gasket is your problem.

The reason your temp is flucutating is the leaking gasket is letting the coolant system get pressurized and creating air pockets. Since air doesn't conduct heat very well, you get the moving temp guage and also the coolant blowing out of the rad.

Tony Hanna
01-21-2007, 01:37 AM
Another way I've done it is to air up the cylinders 1 at a time on the compression stroke and watch for bubbles in the radiator. The compression tester I have is made with a fitting to let you attach the hose off of it to an air hose. Once you hit the bad cylinder it's pretty obvious. You get a constant stream of medium size bubbles coming up in the filler neck until you release the pressure.

LowSL2
01-21-2007, 02:25 AM
I'll be doing some diagnosis tomorrow. On a side note, it ran great today. I just let the engine heat up until the cooling fan came on before I drove it. No problems at all. However the blow off valve sounds like it's leaking at WOT....

Turbo3Iroc
01-21-2007, 03:07 AM
If the head is cracked you will see coolant in the valley. Usually between the center core plug and #3 spark plug. I have seen one on the #2 side though. Hope this helps.

Do you get bubbles in the overflow tank?

turbovanman²
01-21-2007, 06:52 PM
I'll be doing some diagnosis tomorrow. On a side note, it ran great today. I just let the engine heat up until the cooling fan came on before I drove it. No problems at all. However the blow off valve sounds like it's leaking at WOT.... The stockers are common for leaking.


If the head is cracked you will see coolant in the valley. Usually between the center core plug and #3 spark plug. I have seen one on the #2 side though. Hope this helps.

Do you get bubbles in the overflow tank?

I have a cracked head thats leaking coolant into the chamber around the valve seats.


Another way I've done it is to air up the cylinders 1 at a time on the compression stroke and watch for bubbles in the radiator. The compression tester I have is made with a fitting to let you attach the hose off of it to an air hose. Once you hit the bad cylinder it's pretty obvious. You get a constant stream of medium size bubbles coming up in the filler neck until you release the pressure.


Be very careful you have all your hands and fingers away from anything that moves when you pressurize the cylinders. :nod:

Tony Hanna
01-21-2007, 11:56 PM
The stockers are common for leaking.



I have a cracked head thats leaking coolant into the chamber around the valve seats.




Be very careful you have all your hands and fingers away from anything that moves when you pressurize the cylinders. :nod:

Yeah, I should have mentioned that. :thumb:
The pressure will try to to turn the engine. I think I just threw it in gear and set the e-brake after I got each piston to tdc.

LowSL2
01-22-2007, 03:13 AM
Borrowed a friends cooling system tester. There was a huge leak at the water outlet neck where it meets the thermostat housing and the radiator cap wouldn't hold pressure. We replaced the hoses, flushed/back flushed the rad and engine. And double checked for leaks around the head. No problems so far. Just the stupid temp gauge is freaking out like it had too much caffeine. The PCM is reading coolant temp just fine. So I think the sender for the guage is toast. Or there's still air bubbles in the system.

The only other issue right now is the Charge Air Temp sensor. I replaced it today and the PCM still sees 32ºF. I traced the wires from the sensor back to the PCM connector and both wires have continunity. Is this normal or do I have a wiring problem?

LowSL2
01-22-2007, 03:23 AM
I took a video of the gauge with my phone. Should play with Quicktime or Realplayer. Right click, save as.
http://home.comcast.net/~lowsl2/rt/shakes.3g2

turbovanman²
01-22-2007, 03:34 AM
What happens if you ground the CAT sensor signal wire?

I would change the guage coolant sensor, there cheap.

LowSL2
01-22-2007, 03:58 AM
What happens if you ground the CAT sensor signal wire?

Which pin would that be? The black/red wire? I can do that. Would I see a change in the reading on the scan tool? It already throws a code when I unplug the sensor.

Turbo3Iroc
01-22-2007, 04:09 AM
Quote:
Originally Posted by Turbo3Iroc
If the head is cracked you will see coolant in the valley. Usually between the center core plug and #3 spark plug. I have seen one on the #2 side though. Hope this helps



I have a cracked head thats leaking coolant into the chamber around the valve seats.



Do you have the history of what caused this one to crack? I would suspect that this head was over heated vs. the more common casting issues.

turbovanman²
01-22-2007, 04:31 AM
Which pin would that be? The black/red wire? I can do that. Would I see a change in the reading on the scan tool? It already throws a code when I unplug the sensor.

Look at the coolant sensor, whichever wire colour they both share is the ground side so ground the other wire. Yes, the temp should change although I remember someone along time ago chasing this same issue.



Do you have the history of what caused this one to crack? I would suspect that this head was over heated vs. the more common casting issues.

No, I bought it off a running car but of course, me being paranoid had it pressure tested, and sure enough, it bubbles around one valve. Its already been repaired at the usual core plugs. I hope my head rebuilders can fix it.