engine not reaching operating temperature

[rmoe88]

Right before xmas i took my 200 out to have the bottom end rebuilt. I was out of town for some time until recently, and just got to start it up and drive it around. I have some problems though.

If i let the car idle up to temperature it only gets up to ~130* and very slowly. Before the rebuild i had a 165* thermostat in it and it would heat up fairly quickly and stay at a constant ~160*. This time i put in a 195* thermostat. On the road driving i have seen it get up to 160*, but never above that. Its seems to be acting like there isnt a thermostat.

So far i have replaced the first 195* thermostat with a new one, but no change. The car does not leak any fluids. I made sure the thermostat is facing the right way, with the cone looking side facing the radiator. Does anyone have any ideas as to why this would be happening?

Thanks,
Moe.

 

[addo]

What is your source for this information about temperature? How accurate is it?

 

[rmoe88]

2 sources; the stock temp gauge in the dash and a megasquirt efi computer. With the dash gauge im just compairing to what i remember from when i had the 165* thermostat in it. The megasquirt tells me exact numbers, which completely agree with the dash gauge, and is from a second sensor. Im confident in the numbers

 

[x21]

so you have 2 sending units, and a gauge hooked into each?

 

[66 Fastback]

Sounds like you have a very efficient radiator and water pump.
Just Brainstorming.....
Any external oil coolers?
Air in the cooling system?
Bad Grounding on the sensors making them read low?
Is the engine running well? With your EFI do you have some way of looking at the air fuel ratio? One thought I have is that too much fuel could be cooling combustion temps?
Doug

 

[rmoe88]

x21 -- yes

66fastback -- Good brainstorm,
no oil-coolers.
could be bubble in cooling system, any idea how this could cause me to be running cold (or reading that im running cold)?
Ill check the sensors, but i dont think that they both could have went bad at the same time.
Yes the engine is running well. The air-fuel ratio is around 14.7:1 usualy.

 

[66 Fastback]

any idea how this could cause me to be running cold (or reading that im running cold)?

In my old Vette, I once had air in my cooling system after refilling it. The Temperature transducer was not immersed in the coolant and it read low.

However, after sitting there reading cold for a while it quickly increased. I don't know if that is when the the overheating engine heated up the intake manifold or if the thermostat openned and hit it. If I recall it seemed to have run long enough for the thermostat to be open. I think the gauge moved when the entire engine was getting hot due to insufficient coolant in the system because of the trapped air.
Doug