Phil97SVT

We recently installed a 383 and are having some issues with the cooling system...

Motor:
New 2004+ LS6 Block
Eagle crank
Scat Rods
Diamond pistons
2002+ GM MLS Gaskets< Is there is different gasket I should run for the 2004>
AFR 205 heads
G5x3 cam
Stock water pump
90/90 setup
we also replaced the engine coolant temp sensor with a Carquest temp sensor

When we started it up for the first time, we added coolant as we normally do and everything looked fine
Engine coolant temps came up to operating temps normally but once it got to 180-190 where it should have stopped, it kept going up until it sat @ 225-235.

Things we noticed..
The system seemed like it had an excessive amount of air...
Upper radiator hose didn't seem like it was full of coolant
No coolant smell out of the exhaust
Oil pressure 55#
Every reading seems normal
Almost like something is blocking the coolant flow

Problem is the car warms up and won't move off of 230degrees, doesn't go higher or lower.

demonio1023

I been reading the other threads you posted...Have you tried to run it without the thermostat? What processes did you go through, to eliminate each problem or possibility at this point? Give us some more insight so we can help you diagnose it...

Jstyle

Phil when we spoke over the phone I told you I was having the same issue as I am sure ya remember. All of this happened when I got a new thermo you might want to try another thermo I dunno...

Phil97SVT

I've changed:
thermostat
Water pump and thermostat

Todd157k

As stated.. what have you tried/checked?

1. misaligned gaskets/passages?
2. bad t-stat?
3. air trapped in system?
4. something plugging a passage (FOD)
5. bad water pump? cavitation due to air in the system?
6. you're running the motor in the middle of the desert?

is this a trick question and if so, did I win?

Todd157k

ewww. that narrows it down to ugly things like misaligned/incorrect head gaskets or FOD.

DRR

Phil quote - we also replaced the engine coolant temp sensor with a Carquest temp sensor.

When was the new temp sensor installed?
Remove the cap from the surge tank while cold and then start the car and warm it up. With a digital temp probe in the surge tank, confirm new temp sensor is reading the correct temp.

0Randy@DRM

Head gasket is just fine if you have it in right . When we fill cars up we disconnect the bleed hose off the heads. That way the air has a place to get out. I have gotton bad sensors, and t-stats so don't think they are ok.

Randy

Bill Curlee

I looked in a GM 1998 Service Manual and gave Phil the resistance readings verses Temp that was available. There sort of vague. Like -39 deg F ==100,000 ohms and 235 = 70 ohms. That makes it difficult to see if the sensor is accurate. Does anyone else have a better resistance / temp chart??

itsmeek

I would request a cylinder leak down test (not a compression test) in every cylinder with the engine hot, and watching for air bubbles in the coolant reservoir bottle.

Phil97SVT

Whats weird is there are two cars that have the same problem locally...
Phil

Tomulrich

when the engine is hot touch the radiator hoses.....they should be hot.....if not you are vapor locked. Also if you took out the thermostat you need to block off the large 1 1/4 inch bypass inside the pump.

I had the same problem....vapor lock......see if hoses are hot

Tom

Tomulrich

are the hoses hot to touch...uppper and lower. Also if you removed the thremostat you need to block the 1 1/4 bypass in the pump

Tom

LS6 RX7

Interesting...hypertech's thermostats do not work on the 2004 block?!

http://www.corvettegarage.com/produc...-corvette.html

0Randy@DRM

If you do a little grinding on the water pump they work just fine.

Randy

Phil97SVT

04 water pump not block, the 04 water pump uses the new style housing...

TLewis4095

Order a C6 fan & shroud. It will fit & the single large fan moves far more air through the radiator than the C5 duals.

robertp

Today while stopped in traffic because of road construction, I noticed my temp going up to 230 and than back down to 220. It kept doing this and never got hotter than 230 degrees. Outside temp was 86 degrees at the time. Sould I also be suspect of a problem? When I got moving it went back down to about 180.

David A

This is what I was told:
For 2001-2004, the low speed is commanded on when the coolant temperature reaches 226 degrees F. It is turned off when the coolant temperature lowers to 219 degrees F. The High speed is commanded on when the coolant temperature reaches 235 degrees F. It is turned off if the coolant temperature lowers to 226 degrees F. When the A/C is on and the coolant temperature reaches 185 degrees F, the low speed will be turned on when vehicle speeds are less than 35 mph.

LS6 RX7

Most likely there is still air in the system. There is a specific process for removing air in the service manual.

Something like:

1. Leaving the overflow tank cap off, Start engine & bring the Coolant temp to 170*. Add coolant if necessary. NOTE when TStat opens if there is air in the system it will burp and overflow. BE CAREFUL. DO NOT HAVE YOUR HANDS OR FACE near the overflow tank filler neck.
2. Reinstall cap and pressurize system.
3. Rev engine to 3500 RPM for 1 minute
4. Rock the revs between 1000 - 3500 RPM repeadidly for 1 minute.
5 Temps should be up to 220*
6. Shut off engine and let cool slightly
7. After 2-3 minutes SLOWLY and CAREFULLY remove cap to depressurize system.
8. Note fluid level and add again if necessary.

REPEAT until no more fluid is necessary after cooling down.

NOTE adding 2 pints of RED LINE Water Wetter will help in removing air.

ALSO remember to cycle the heater and A/C during the last couple of hot runs.