Engine Weird Cooling Issue

[ImportSlayer347]

I am having a strange issue the last couple of days. As long as I am idling at a stop the temp gauge slowly climbs until it hits 195 then my electric fan kicks on which is how I have it set. However, as I am driving, the temp slowly falls until it drops all the way to 150. It usually stops at 180 as I have a 180 degree thermostat. Then if I stop and let it idle, it climbs back up to 195 and stays. I cannot figure this one out. I have an Auto Meter mechanical water temp gauge. I am running a 50/50 coolant mix (AMSOIL coolant and distilled water). Any thoughts on this weird problem?

 

[ImportSlayer347]

My guess is the thermostat is sticking open.

 

[Grabbin' Asphalt]

that is very possible

 

[ImportSlayer347]

Nope. Thermostat is good. I replaced it anyways since I had it apart. Still doing it. Anyone have any insight?

 

[Grabbin' Asphalt]

well, is it correctly burped, ...on a slight incline etc??? i really thought it would be the stat.

 

[ImportSlayer347]

This is driving me crazy. I thought about flushing the system, but I don't wanna end up wasting all my coolant if it isn't gonna help.

 

[Grabbin' Asphalt]

replace the temp sensor??

 

[ImportSlayer347]

Its a mechanical gauge, I would have to replace the whole gauge. I think its reading properly because when it is displaying 195 my fan kicks on and when its climbing after a cold start i feel the thermostat open when the gauge shows 180.

 

[HISSIN50]

The stat sticking open periodically seemed most likely.

If the capillary tube isn't mounted in the stock gauge sender location, where is it located? If it's in a hose adapter or the t-stat housing, that could lead to incorrect readings.

When it 'acts up' (appears to stay open below the t-stat rating), have you put on a mechanic's glove (or whatever one feels is required to touch a hot surface) and squeezed the upper rad hose to see if you can tell if coolant is flowing?

 

[ImportSlayer347]

The capillary sender is mounted in the stock gauge sender location. Its on the top of the intake manifold in the rear center. I checked to make sure the tubing isn't pinched and it seems ok. I have been unable to check with the touch test because it only drops while I'm driving. Soon as I stop and pull over it starts climbing right away back up to 180-195.

 

[ImportSlayer347]

I ordered another gauge to see if that is the problem.

 

[HISSIN50]

If it climbs from 15X*F to 195* in less than 30 seconds (time needed to pull over and check the hose), a bad reading is not out of the question.

To confirm, the stock gauge sender is in the *front* of the lower intake, driver's side. The rear port doesn't get very good coolant flow and can read erratically.

 

[ImportSlayer347]

The gauge has been in the same spot for 5 years without a problem. I did get pulled over when the gauge was reading 160 and I saw that the electric fan was running which only come on at about 195. Now I am 90% sure the gauge is the problem. I just wish I knew what would cause the gauge to suddenly go bad.

 

[HISSIN50]

It could just be binding up.

 

[ImportSlayer347]

Hey HISSIN50 do you know what the port on the back side of a holley systemax 2 lower intake manifold is for? Thats where my gauge sender has always been. Something tells me it was intended for something else.

 

[HISSIN50]

All I can answer for is the stock intake (I'm not sure why an aftermarket unit would be different. Maybe someone else can speak to your particular intake).

With regard to the stock intake, there's obviously a coolant port back there, but the issue is that the flow [back there] isn't very good. It's not a bad place to put the stock sender (since the stock gauge is kind of inaccurate), which then allows the stock sender location to be used for the aftermarket sender/cap tube.

 

[ImportSlayer347]

Where does that coolant line go to from that back port?

 

[HISSIN50]

I'm not sure if this is what you mean, but there's no coolant line. There's just a plug installed in the port.

 

[ImportSlayer347]

 

[ImportSlayer347]

That's the port that my aftermarket gauge in hooked into. I am not sure what is supposed to be in there.