Hi,

I had my 97 4.6L idling for about 20 minutes today inside a warm garage. I had a SNAP gauge hooked up to check on up codes and such. There are no codes.

The ECT reading on the snap on gauge was reading 180F and the infrared reading on the thermo housing was reading 150F. The coolant gauge inside the truck has always been on 1/3 of the way up.

Is this normal?

The fan was running the entire time with the hood up when testing. I did replace the thermostat last year from AutoZone, but I don't remember what temp thermostat it was.

Thanks,
Frank

 

Well, here in Knoxville in winter time, running on interstate mine reads 188.. during the summer, i typically see between 195 and 200-204 running down interstate. That is from my Gyphon programmer. I have had the system flushed twice, 152,000 miles, factory t'stat.

 

According to your readout the coolant temp is just a bit on the cool side.
Normal is about 190 to as high as 210.
I would not worry about it. Depends on what point in time the reading was taken.
Meaning at a time the thermostat was open or closed. That can cause the temp. to swing over a short range.
Only concern is if the temp is too low can cause fuel consumption to rise somewhat.
The ECT sensor is part of the fuel determination logic as the only way the PCM has to know what the termp status is for cold starting and hot running/restarts etc.
You mention the fan. If it is the stock clutch type it will never actually stop turning but always have enough friction in the clutch to keep it moving.
A way to test the clutch is to use a timing light connected to any cylinder's spark plug wire and shine it on the fan blades.
Over time of several minutes you can see it sync up and go out of sync as the heat sensitive clutch works in response ti the radiator temp changes as the thermostat opens and closes.
If the cluch tends to lock to running hard on too much of the time, the coolant can be lower on average or may indicate the thermostat needs replacement or both.
It's a judgement call based on what you see happening.
Good luck.

 

Both refering to thermostat and fan clutch?

Thanks for the info bluegrass. Here is some more inputs.

I realized that the car was running the whole time with the heat on full blast in the defrost mod. The top radiator coolant line was also cool to touch.

My MPG may be lower than normal. It gets 10.0-12.5 MPG. Most of these readings have been taken during the winter early spring here in Ohio.

What about also replacing the ECT sensor?

 

These are general comments related to the cooling and how the PCM can respond.
When new and all is within original specs, it is the designed baseline for performance.
As age and wear progress, the Ect sensor reistance can change, the thermostat can change it's thermal response to the coolant and the fan clutch can change and either cause overcooling or undercooling.
Because the ECT/head temp sensor feeds it's signal to the PCM, any changes in the system is detected by the ECT and can change the fueling table baselines and cause increased fuel consumption form any and all the above changes in parts performance.
Any of these items that go to the edge of limits canl affect performance.
.
Often this is part of the reports of older trucks getting poor fuel mileage or even higher end mileage than the normal average if the tolerences happen to all shifts toward the lean end of the fuel tables.
You would have the test for each part's performance to detect any one out too far.
Most of us don't bother unless there is a very poor mileage indication on a long term basis from what was acceptable.
Throw in a large change in ambient temperatures, changes in gas formulation and aging of OX sensors and you get a variation all over the map at any given time.
Associated with these things are those who look to aftermarket air intakes and filters trying to correct for these aging parts.
I usually doesn't work out to much advantage.
The stock system has more than enough airflow capacity.
Good luck.

 

what temp is the stock thermostat rated for?

195?

 

I believe it's 192.

 

ok, I just bought a 195 today to swap out tomorrow.

I might have put in a 180 last year.

 

Mine was running cool last year... even in 5* temps it warms up to 298-204* now

 

So I swapped out thermostats yesterday.

The old one was rated at 195, but might have started dying.

The new one I got did not fit correctly since the o-ring rode around the thermostat, i'm guessing it is for the 4.2 and not the 4.6L. So I took of the o ring and put the old o-ring above the new thermostat (you can see the old o-ring in the back ground of the first picture.)

The temp now reads 190-195 F.

Anything more I can do?