Engine Help cooling issue

[Old Sarge]

Ok new to this so I hope I’m doing this right
I have a 91 fox with TFS 1 cam 165 heads, and AOD. Put this motor to get her and have been running it around town for about 2 months. Now when driving it the ten gage sits in the middle to slightly below. The issue is when at idle for more than 15 or 20 mins gage goes up and pushes coolant into over flow tank but doesn’t boil. I changed the radiator to a 2 core and replaced the fan clutch. Still the same. Doesn’t have the usual head gasket signs so I block tested and all good. No leaks any ware and hold pressure. Cap too is good. T-stay is a 195 and new. Is it a flow issue? Do I need to upgrade water pump or change t- stat. Or head gasket? Heats up quickly with ac on as well also when it cools fluid returns back to radiator. Been driving this car around for 2 months and it just started this. Any help would be appreciated thanks

 

[General karthief]

First you need to put a real temp gauge in it so you know what your actual temps are.

 

[Blown88GT]

One or both of these remain:
Insufficient air flow through radiator.
Insufficient coolant flow through radiator.

 

[JD1964]

If this car has underdrive pulleys, they could contribute to temp rise during extended idle periods

 

[Old Sarge]

No under drives on it, got a high volume water pump coming, will see what happens
I will have to agree on fluid flow. Even with no t- stat I can squeeze the top hose flat with no effort

 

[Gs1987GT]

Yeah that's not right. Seems like there is no pressure in the system if you can flatten that hose so easily.... maybe try another rad cap?

 

[Old Sarge]

Well thanks for all your help, installed the new water pump from Gmb, not sure what makes it high looks the same as old one even the impellers, and 192 t stat. It cured the over flow problem in the overflow tank. But still gets a little warm if it idles more than 20 mins with ac off. Put a new motor craft cap on and and seems to be ok now with a/c off. A/ c on at idle it takes a good 15 mins to creep up to around ware the “o” is on normal and quickly comes down when in motion. Normal cruising and traffic lights sits solid at between the M and the A. I can live with that for now lol. My 89 ran a bit warm with the AOD in it too so I guess the extra drag on the engine may have something to do with it. Thanks to you all out there for the help, been hitting up this form for years. Now finally decided to join

 

[General karthief]

Enthusiasts have to remember the these newer (computer controlled cars) run at a higher temp than the 60-70's cars. Kinda hard to get used to. Where 210-220 used to be a cause for concern now it's normal.