I've been banging my head against the wall for hours. I keep overheating at idle.
All hoses are good, thermostat is positioned with the spring facing the motor (coolant flow hits the spring). The orientation is correct.

I've bleed and bleed, but still think I have an airlock. I'm measuring temps of 208 on UG (and climbing) at the manifold, but the Stat housing is only 135ish. And colder after the stat. I dropped the stat in a pot of water and confirmed proper operation.

My setup is identical to all the ones in the DIY's (water temp sender w/ bleed screw).

I'm stuck. Any advice before I put the old setup back in?

 

Did you drill the hole in the thermostat?

 

I did not. What's the purpose? To bleed air?

 

I am measuring a delta of over 20 between a six inch section of hose.
I can't seem to get the "hot" water up to the stat to allow it to open.

 

I'm gonna try drilling an 1/8th hole in the disc of the stat. Hopefully, this will allow an "trapped" air to pass through. We'll see...

 

If the hole doesn't work then try dropping the stat in a pot on the oven to see if it opens when it's supposed to. It could just be a bad thermostat too. Actually, try the pot thing first so you can still get a warranty replacement.

 

Good thought but, I already cooked the stat - it opens marginally at 170ish then fuly opens at 180ish. Checks out fine. I kinda was hoping it was bad.

I think the 1/8" weeping hole in the disc may do the trick.

 

That was my issue! Excessive pressure behind the Stat. Drilled a 1/8th" hole in the disc, oriented the hole to the 12 o'clock position (facing up)...Boom.

Temps at idle peak at 199.4 then drop (as the stat opens) to 177.8. The cycle continues. Slowly climbs back up to 199.4 then, back down to 177.8. May have a little air still trapped, try bleeding tomorrow morning.

Does this seem like proper behavior for this application? Or should I have a stable consistent idle temp? Regardless, I'm happy.

 

I have the same setup without the hole (which makes bleeding air more difficult) and my temps don't fluctuate nearly that much. I wonder if you don't still have some air. As long as it isn't overheating the air should work it's way to the expansion tank eventually... I bet you see your coolant level drop a tiny bit over the next week.

If I redid the setup I'd put the valve at the highest possible point in the hose and drill a hole in the thermostat as you have done. On mine, the highest point is where the thermostat is because of the upper fan housing.

Also, check this out (posted by another member)... no air bleeding no air fourteen bucks. A note 90 degree fitting just above alternator.

 

I did the inline thermostat mod as well and didn't see the point of the holes. Mine overheated as well. Started with one hole and it got better. I eventually drilled a second hole and all my problems went away. The only thing I can figure is that there has to be enough coolant flow even when closed for the hot coolant to reach and open the thermostat. Beats me, but the two holes worked for me. I had one at 12 o'clock and 6 o'clock and 1/8" as well.