My 01 m6 coupe is running hot. Not like the normal 220 degree running hot because the air damn isnt there or the radiator has stuff on it.

But withing about five minutes of starting the car the temp rises to about 240 and stays there for about two or three minutes then falls to around 200. I have no idea what is wrong or why it would do that. please help.

 

One possibility is air in the cooling system.

 

Thermostat slow to open?

 

This is a good place to start. Make "SURE" there is no air in the system.....do a super burp and if it continues, then check the t-stat to make sure you are getting a opening start at 187 degrees.(put it in a pot of boiling water and see what temp it opens at).

Then, check the hoses, check for debris between the radiator and the
A/C. Check the radiator cap for a 15-16 psi seal. Check the system for a good 50/50% of fresh DexCool and distilled water.

Get back to us.

 

Burp procedure:

Start w/ a cold engine
Remove rad. cap
Idle for 1 minute
Install cap
Cycle RPM from idle to 3000 until coolant reaches 210F
Shut off engine
Remove cap very slowly
Start engine
Idle for 1 minute
Install cap
Cycle RPM from idle to 3000 until coolant reaches 210F
Shut off engine
Remove cap very slowly

Repeat the above as many times as necessary
Top off

 

And if the above doesn't work, loosen the bolts on the "head to head crossover bleed tube".

 

I think this is the best way. Worked for me like a champ. But how did he just get air into the system?

 

Don't think the high speed fan even comes on till the 230's-does not sound like it's too far off the mark. And you don't really have to BURP this system, just make sure it's at the correct level(s) hot and cold. The surge tank it the high point of the system-no classic "BURPING" required.

I'd clean the outside of the radiator-known junk collector.

 

^ 235 actually. Op are you seeing 240 on the digital readout or the dummy gauge?

I would get a air pressure gun and clean out th condesnor and radiator of the gunk and you should see some better temps.

"The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

This is right from the tech manual.


here is the thread about burping the system from the heads. IMO the best and only way to do it.

http://forums.corvetteforum.com/c5-t...erheating.html

 

Stock settings are:

When your AC is on the fans turn on at low speed (fan speed not vehicle speed) at 185. High speed kicks in at 194 degrees.

When your AC is off the fans turn on at low speed at 226 degrees. High speed kicks in at 235.

BTW, I know you said it's not an issue but you really should check for debris between your radiator and condensor... You have no idea how big a difference that can make in your coolant temps...

 

here are the stock fan settings:
#1 on at 226* off at 219*
#2 on at 235* off at 227*


settings with A/C on:
#1 on at 35 MPH or
#1 on at 185* or
#1 on at 219 compressor PSI
#2 NO MPH ON SETTING
#2 on at 235* or
#2 on at 255 compressor PSI

BOTH fans OFF at 90 MPH
( A/C OFF RPM) 4895 -when A/C is disabled fans setting revert back to
NON A/C settings

Sounds like to me your thermo is just getting stuck or is opening very slowly--Reason for the temp spike
IF your radiator intake is clean---And you have "burped" the coolant system to remove all the air-- I would just get a new thermostat--
You will have to re set you fan settings to take advantage of the lower thermo or would won't see much of an inprovement
I always install a 160* themo----It won't run that cold--and despite what you read is not harmfull on the engine and actually can make some HP and make everything last longer under the hood
With a 160 thermo it willrun about 185* most all the time--On a hot day in traffic it may go to 195-200 at the most
Recc. fan settings with 160*

#1 On at 190 off at 182
#2 On at 200 off at 191

leave all the A/C related settings STOCK

 

Thanks for all the advice guys. Im going to burp the system, and have the whole system flushed

 

If it has never been done it would be a good time to do a simple cooling service and replace the hoses and thermostat as well as the water regardless of the problem.
One addition I would like to make. The fans both run when they are on. At low speed they simply run in series through one relay and because the resistance is doubled(two motors running) they run slow. When high speed is triggered the first fan gets directly grounded and an additional relay powers the second fan so both fans get full power individually and run faster (parallel circuit). Relay 3 simply toggles between series and direct ground.
This is not necessary for your problem, but keep in mind later cars do not bleed the rear of the cylinder heads. My '99 does, but I took it one step further and tapped the ports then plumbed everything with AN-4 line to the surge tank. That way the little hard to find seals at the bleed tubes are completely eliminated from the system so one less failure point.

 

Flushed all the old coolant, replaced the old thermostat with a new 187 degree one,
(didnt stock 160 degree) filled with new dex cool and water, burped the system. working like a charm now.