OK, I am getting frustrated now. Thought I had the problem with the new 180 Hyertech stat straightened out. Drove it for a couple of days and no engine code. Then one morning the engine light comes on and it's the p1281 code again. Again I try burping the system but get no bubbles, etc. I reset the computer. Next day I drive it and no problem (temp outside is in the 50's). Then yesterday morning I leave for work (outside temp now in the 30s) and sure as sh#* the engine light comes on again. Needle is barely getting past the first line on the temp guage. Does the outside temp make that big of a difference here? Is there a problem with the stat itself that it is opening too early when it's cold? I didn't drill the hole in it when I put it in (never had to before on any other stat). I have read some posts that the hypertech stat is crap. Could that be it? If I get one from napa will that be any better? I am wondering now if I should just put a stock one back in. Anyone?

 

When you burp the system, do you leave the truck running with the heat on high and cap off to monitor level? Just let it run a while. Occassionally put the cap on loose to keep from burping out and bring the RPM's up, hold for a few and check again. Can't imagine it just getting to the first mark.

 

It sounds to me like the Hyperstats are just hunks of junk. Shott's flat out broke on him too, the pin actually poped out of the housing.

 

mine has been working fine so far.. come on right around 180 degrees.. like 1/4 the way between the 1st line and the middle.. i would really just go get a new stat and try it out

 

I was letting it run with the heater on each time. I think I am just going to try putting a new stat in to see if that helps [>:]

 

Many of the stock 2nd Gen thermostats are 'standard grade' Robertshaw/Siebe models that have a steel upper frame and brass underarms. The brass underarms tend to crack. This happened to my 1995 back in 1999.

The Hypertech thermostat also seems to have quality control problems.

I have had a Robertshaw 330-180 thermostat quit working in the closed position.

The Stant standard grade 205 I tried had no failures, and a Super-Stant 180 also has been defect free so far.

Having run 180, 195, 205 thermostats - and having run for 2 days with no thermostat/distilled water/oxalic acid Prestone Superflush at around 140 degrees coolant temperature - I can tell you that there is very little power change with different thermostats, little pinging change on 87 octane, and only very small MPG changes during 310 mile test runs.

My advice: don't expect much from the labor and $ you put in thermostat change outs.

At 140 degrees on 99% distilled water there is slight pinging reduction.
At 260 degrees with Evans NPG coolant the idle is a little smoother.

 

My guess is - like shott - you got a P.O.S. thermostat from Hypertech, and it is staying open all the time or it broke like shotts. I used a NAPA Premium 180 ($6.99). It was well built. I didn't drill it either. Have had no problems with air bubbles or anything else. Appears on initial calculations that I gained about .5 mpg after the install.......

I would change it out for a NAPA stat.

 

Stant is one of the older, more reknowned thermostat makers in the coutry. They've been making them *almost* since cars have been around.

 

It does appear that the outside temp is having an impact here. Today it was in the 50's and up and the temp guage got a little higher and no CEL. I picked up a 180 degree stat from NAPA and I will probably just change it out. Should the outside temp have that much of an impact?

 

It might, if it below freezing it takes a little while to get the temp under the hood up, especially with that fan action going on under there. It might help if you run the truck at a fast idle for those cold days (between 1-2 K rpm) for about 5 minutes to get the flow going ya know. Helps it get up to operating temp nicely.