changed thermostat to 160 now overheats

**booyako** · 07-25-2010, 08:05 AM

Hello everyone did I not do somthing correcctly any help would be apreciated. I changed it to 160 and temp goes up past 230 and i shut it down. i thought it was junk so I put the stock thermo back in and it is doing the same and yes i check the coolant. is there a step in changing thermostats i dont know about? my car is 01 z28 thanks for your time please somone Help!

**00ls-1** · 07-25-2010, 08:15 AM

very possible it has an air pocket in it. take the cap off and start the car leave the cap off til the car is warm

**00ls-1** · 07-25-2010, 08:17 AM

the stat wont make a difference unless the fans are programmed to come on at a lower temp

***Ed Blown Vert*** · 07-25-2010, 08:34 AM

The thermostat will only help on the freeway unless you program the fans.

You have air in the system.

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**Firebirdjones** · 07-25-2010, 08:50 AM

Sounds like air stuck in the system. Pretty typical of LS1 4th gens.
I get it every time I flush the coolant and/or change thermostats.

I have to keep shutting the motor off to cool, squeeze hoses to work the air out, start back up, and repeat until it's running normal.
Seems GM didn't put bleed valves in the system like the LT1's had. I never had this problem with our LT1 4th gens.
But it's going to happen with this goofy cooling system design. The thermostat is only halfway up the engine block and going to the lower hose. Bassackwards from conventional stuff.

Might help if you crack a hose open while filling with coolant, I was just never willing to make the mess it will cause.

**00ls-1** · 07-25-2010, 08:52 AM

i put the 160 in my car last weekend and had the car running as i filled the system and no problem at all

**pajeff02** · 07-25-2010, 08:57 AM

Changed ours out to a 180 and it airlocked on the first start up. Bounce the car a bit on the suspension and rock it side-to-side as you add more coolant to the radiator. You can also start it and after you build a little heat in the motor rev on it just a bit to try to work the air out. Your top hose should start getting warm by 170 -- if not, you are likely still airlocked.

**cammed goat** · 07-25-2010, 09:01 AM

When I replaced the water pump on a customer's 02 Suburban, I left the cap off the recovery tank and let the truck run with fresh coolant to let any air out of the system.

**Cutlass** · 07-26-2010, 06:56 PM

thats why I love my AirLift. Hook it up to shop air and it sucks all the air out of the cooling system down to a vacuum of 25in hg. Unhook the shop air, dip the hose in a drain pan of 50/50 coolant, turn the valve and the coolant gets sucked into every last part of the cooling system. You can literally fill the cooling system in 5 minutes and go out and drive it. No messy burping or bleeding cooling systems.
Oh additionally it has a diagnostic feature to it also. If the system doesn't hold vacuum, then you know its gonna leak. I discovered many times I've forgotten an hose clamp or a hose all together. better to find out first before spilling coolant everywhere.

**pajeff02** · 07-26-2010, 06:59 PM

Very cool! I've never heard of this before.

**TerribleTed** · 07-27-2010, 05:29 AM

amazing,,,,I have numrerous times drained and refilled mine with ZERO issues relating to heat..
Must be blessed by the gods -my car that is,,,not me

**DaddySS** · 07-27-2010, 05:29 PM

leave the cap off, fill it to the bottom of the fill neck, start the engine and wait for it to warm up and the thermostat open (wou'll see the coolant start to circulate and the level should lower. Fill it the rest of the way, close the cap, fill the recovery resevoir to full hot, and you're done.

Cutlass: Nice tool by the way.

**pajeff02** · 07-27-2010, 05:36 PM

Some engines can be a real pain to avoid air locking. Years ago, they added the check ball in the thermostat housing to allow air to bleed out as the system was re-filled. One of the best ideas ever, but somehow they can still air lock.

**Firebirdjones** · 07-28-2010, 09:08 AM

Originally Posted by pajeff02

Some engines can be a real pain to avoid air locking. Years ago, they added the check ball in the thermostat housing to allow air to bleed out as the system was re-filled. One of the best ideas ever, but somehow they can still air lock.

Yep, I drill a pair of 3/16" holes in all my thermostats. Old trick.

**zeetwentyeight** · 07-28-2010, 10:00 AM

I have had this same problem.disconnect the line going to your hades and through your TB fill the coolant through the lower radiator hose till a soild stream of coolant comes out of the metal line coming off the heads this should completly bleed the system. There might better methods but this worked very well for me.