Hi, I have a 2000 FRC with an LS2 block, LS6 heads and Intake manifold. I'm currently running the stock 2000 water pump and the stock 192 degree thermostat that has the Weep hole in the housing. Can some one tell me what I have to do to run a new style water pump like for a 2005 ls2 corvette? I tried running the car with the 2005 water pump and thermostat that came with the water pump from GM for a 2005 corvette and it will not work as expected. The car runs hot as soon as you start down the road reaching temps in the 230 degree range in less than 5 miles. I put the original water pump and thermostat back on it and everything worked as expected and the car runs at thermostat opening temp.

The 2000 style thermostat won't fit in to the newer style water pumps for the 2005 and up other wise I would have done just that and I suspect the water pump would have worked as expected.

I assume there is a slight difference in the 2001 and above cooling systems that allow for the non weep hole thermostat housing to work. Any ideas?

Thanks

 

There is no reason you cannot run the later water pump with the later thermostat and separate thermostat housing. A possible reason for your experience may be that the new thermostat is bad or air got trapped in the heads.

If you still want to run the later water pump, I would get a new thermostat, test it in boiling water to make sure it opens and after installation burp the system and or use the Factory Service Manual purge method which requires you to idle the engine for one minute, fill the surge tank to 1/2 inch above cold full, install cap, cycle the engine from idle to 3,000 rpm in 30 second intervals until coolant reaches 210 degrees F, shut down and refill to 1/2 inch above cold full. Note that the surge tank cap has to be removed slowly to relieve pressure when hot.

 

Thanks Jim,

I tried all that already, I went out and bought 2 Brand new GM thermostats verified that all 3 GM thermostats worked in boiling water and none of them made a difference when I put them in the car, I tried an aftermarket thermostat as well from CC. I did the burping process 3 times with no changes, but as soon as I put the thermostat with the weep hole back in everything works as expected with no issues.

 

Have you tried running the new water pump without a thermostat? Might be a long shot but maybe your pump is defective such as the impeller is installed backwards and not moving the coolant effectively.

 

No, I didn't try that because I could see that the coolant was moving as expected in the coolant reservoir. If the impeller was on backwards or broken you could tell as no coolant would be moving in the reservoir. But thank you for your idea, anything is possible nowadays!!!!.

I may go back and try that though to see what happens... I would expect the car to run cold initially and then stabilize at whatever temp it could reach depending on outside air temp and how hard I was driving it.

I'm pretty confident it has something to do with the Weep hole in the thermostat housing that GM did on the 97 - 2000 corvettes before they changed it in I think it was 2001 or 2002.

 

Well, it is still a mystery, here are some things to think about. I think up through 2001 the thermostat and housing were integrated. 2002 and later the housing is separate from the thermostat. Here are pictures of two integrated units I have run without issue, first an AC Delco OEM, second an aftermarket.



Note that the OEM has a bleed hole at about 8:00 in the housing AND has circulation holes in the disk that seals the flow.



The aftermarket has a bleed hole in the thermostat disk at about 4:00, no circulation holes in the sealing disk.

Probably should give a careful look at the thermostats you are using as well as the housing(s). Maybe a mix between aftermarket and OEM is stopping the bleed which occurs as you fill the system with coolant.

Another possibility is a block or partial block in the coolant air bleed system from the heads. A car that has had old coolant in it can have sludge which can impair flow through the small coolant air bleed lines and leave air in the heads. 2001 and later LS1s have the rear coolant air bleed ports blocked and not connected which can make the situation worse. Many of us 2001 and later LS1 guys have reconnected the rear ports on the heads to the front coolant air bleed line for better assurance of getting air out. Not sure about LS6 heads or your installation. The LS6 manifold does not have enough room under it to allow the 2000 and earlier air bleed line from the rear ports to go under it without modification.

Instead of the FSM air bleed method of 3000 RPM etc. I use a very positive air bleed method whenever I open the cooling system on my car. The following picture shows the coolant air bleed line from the rear head ports Teeing into the front line after the throttle body. Note the connector about mid right on the way to the radiator. I disconnect there, block the tube going to the radiator and bleed directly to a container on the floor under cooling system pressure. It has taken as much as a quart of coolant flowing out before air bubbles stopped.

 

Jim, thank you for this great insight... I hadn't thought that deeply on the thermostats. I know the basics with the bleed hole but never thought to look at the sealing disk and the difference they have. I have an after market 180 degree that works fine but requires me to use a radiator block once the outside temps drop below 50 degrees or so. I will take a look at that and see what I can put together to work in the 2005 water pump. Thanks again.

 

I forgot to mention that the reason the aftermarket thermostat, which is advertised to be a 180 degree thermostat, is not in service is that it was rough during warm up, overshooting at first and ultimately did not run at a little over 180 degrees. I went back to a new AC Delco, which allows temperature to come up smoothly and operates at advertised temperature, about 190 in day to day driving, 190- 200 after a 20 minute track session on a cool day.

Added info- Dewitts radiator with engine and transmission coolers, air to air transmission cooler in front of the condenser, Improved Racing engine oil thermostat and SS braided hoses to oil cooler, B&M finned aluminum transmission pan with two quarts extra capacity, Sac City Cool It (activates high fan with fob) NEW air dams, 3.73 / WaveTrac rear drive, A4, stock engine. Still my challenge to drive well after nine years of road course tracking.