Hypothetical question - Gen I

[98Cobra]

If your Gen 1's engine temp sensor never came off cold - what would you check, in what order?

[rickgig]

Wires?

[Sixpipes]

Stuck open thermostat would be number one...

[98Cobra]

Stuck open thermostat would be number one...

What other symptoms would that cause? Assume driveability is unaffected. If sitting idling in park, occasionally the idle might become rough, but then smooth back out.

[dboat]

What other symptoms would that cause? Assume driveability is unaffected. If sitting idling in park, occasionally the idle might become rough, but then smooth back out.

wouldnt it run rich since the temp is lower?

[Flats Man]

If the Gen 1 runs too cold, in will never go into the closed loop and fuel economy will suffer. It should run just to the left side on the N on Normal. I just drove Dennis's Rat Rod Gen 1 to Florida and it was doing the same as yours and getting pretty bad gas milage. I changed the thermostat and the temp came up to normal and I got 16 mpg enroute. On a cold day last winter, enough cold air was going through my radiator that my truck went into open loop and my F/A ratio went from 14.7 to 10.5 until I came off the freeway and got into traffic. Then it went back to 14.7. At 10.5, it will idle a little rough. I hope this helps. Basically do what Dennis said and change the thermostat first.:icon_mrgreen:

[L8 APEX]

I have seen the temp sender and the gauge clusters fail. I think you can measure the resistance off the sender and if you unplug it then the gauge should read high I think..

[Wht95Lightning]

With a 180 stat, My truck will not warm up enough to go into closed loop if the ambient temp is below 40 degrees. I have to block off half the radiator (or more).

[98Cobra]

I should say that the gauge showed normal operating temp one day, and the next morning never moved off cold, and hasnt since. So I dont think its the cluster or gauge itself.

What thermostat would you guys recommend? 160 degree?

[98Cobra]

Are there any how-to's you guys know of for changing the thermostat?

[Chris94L]

I'd go ahead and put in a stock 192-195° thermostat. Its a really simple process. Drain coolant below level of thermostat. remove the 2 bolts holding the thermostat housing to the intake. Scrape gasket off of both surfaces. remove and install thermostat into housing making sure it is properly oriented. I like to use a gasket with the sticker on one side to hold it in, then bolt the housing back to the intake, refill to proper coolant level, and thats about it.

[L8 APEX]

I would buy the 10 dollar 180' stat. I think those take a gasket which I like to smear a thin film of ultra black pookie on. Maybe surface the water neck on a belt sander.

[99WhiteBeast]

Did I miss something? When did you get a G1? Did you buy my old truck from Tony? (Adam's dad)

[98Cobra]

Well, I wasnt going to say anything yet, but yes - I am back in the fold, with a Gen I. I would have bought Tony's truck, but it sold before I could move on it. :( Instead I bought the one that was for sale recently in the forums from a Ft. Worth police officer. Its in decent shape, although nowhere as good as your old truck Steve!

Sorry for all the noob questions. What sucks is everything worked great the day I bought it, and the very next morning the gauge acted up. Isnt that how it always goes. :)

[99WhiteBeast]

What sucks is everything worked great the day I bought it, and the very next morning the gauge acted up. Isnt that how it always goes. :)

Yep the nature of the beast with these old trucks but they are a blast to drive. The Fort Worth truck looked very nice too:tu:-congrats and bring it to the meet on Thursday if you can.

[98Cobra]

It will be at the meeting on Thursday. Hopefully I can figure out the Tstat change before then.

[Mark #2]

It will be at the meeting on Thursday. Hopefully I can figure out the Tstat change before then.

I have always found Haynes manuals to be very helpful, get one.
Flat sanding the filler neck, new gasket, and black RTV are great suggestions. I have done these on the K5 with good results.

Spray the drain valve on the radiator with liquid wrench tonight when warm and in the morning before driving.
Also the mounting bolts for the filler neck. This is the highest risk, breaking something on an old truck.

If you think you need help, WWFB garage can be open tomorrow evening, I will be doing some maintenance on the K5, time to pass inspection again.