temps rise, then fall

[cowboyzr2]

Definitely a cheap place to start...
How does your coolant look? Is it old Dexcool?
First thing I did on all 3 of my Vortecs was drain the Dex out and put back in green

 

[SunlitComet]

they can. it was not getting it exercise. and when you replace it fill the block just enough that the coolant level it touching the bottom of thermostat when installed.lay the thermo in place and wipe of any excess coolant and install housing. that should get it to start working on the first heat cycle. with that back together and with the rad cap off the whole time keep the rad filled with coolant as you squeeze the top rad hose to get rid of as much air as possible. eventually it will fill it self up. cap it start engine and run it to hot. when you shut it down for what will be for more then 1 hr make sure the reservoir is about 1 inch over the full to hot mark. at that point do your regular driving and any last remaining air will bleed thru that tank. just keep an eye on the reservoir tank and you will see it settle out. adjust as needed to make sure you dont suck in any air from not topping off correctly.

---------- Post added at 05:20 AM ---------- Previous post was at 05:17 AM ----------

Definitely a cheap place to start...
How does your coolant look? Is it old Dexcool?
First thing I did on all 3 of my Vortecs was drain the Dex out and put back in green

why are try to spend more on unneeded maintenance. there was and is nothing wrong with dexcool if system is properly maintained.

 

[99tahoeinwv]

Ok thanks for the input guys. Ill try and tackle it this weekend

---------- Post added at 11:49 AM ---------- Previous post was at 10:28 AM ----------

i flushed the radiator last year, if i didnt get the mix right or had too much water in it is it possible that part of it froze and that is causing the delay? just grabbing at straws before i attack it.

 

[SunlitComet]

not if you hit the red line on the temp it is definitely melted by then. look into the thermostat issue. sounds like it it sticking real bad.

 

[99tahoeinwv]

ok, i thought so too that it would have melted. i will jump on thermostat this weekend. one other question, at the front of the thermostat housing is a sensore and i noticed when i did thermostat last year there is a ground wire on the front bolt. is that ground for that sensor? and im assuming if the gauge is moving the sensor is working correct?

 

[SunlitComet]

the sensor on the thermostat housing is for the computers reading of coolant temperature. the sender the feeds the dash gauege in on left cylinder head between exhaust port 1 and 3. it has one wire on it. the grounds wires there are not for the sensor specifically. they are grounds for pcm related stuff.

 

[rolfsent]

My 1997 Yukon was just doing the same thing so I changed the thermostat and that didn't help. I ended up finding coolant under the truck the next day and it was coming from one of the radiator oil cooler lines. So I replaced the radiator and flushed the coolant and the problem has been gone ever since.

 

[99tahoeinwv]

is there any easy way to test the thermostat? stick it in the pot on teh stove maybe?

 

[retorq]

not if you hit the red line on the temp it is definitely melted by then. look into the thermostat issue. sounds like it it sticking real bad.

Not necessarily, if the bottom hose is frozen solid there will be no flow, the temps in the upper engine will skyrocket and probably turn into steam and start cracking stuff while the 'stuff' in the radiator will be below normal.

---------- Post added at 12:17 PM ---------- Previous post was at 12:17 PM ----------

is there any easy way to test the thermostat? stick it in the pot on teh stove maybe?

It's $5, there is no testing, you go get a new one and quit being a cheapskate.

 

[99tahoeinwv]

yeah yeah retorq, i know im gonna hopefully jump on the thermostat tonight. gotta make sure this thing is good to go before grass cutting season starts. thanks for the input