I have a 2001 LS S-10 Blazer and I watch the coolant gauge run all over the place. When it first warms up it will be fairly stable, but then it will start to heat up to the point of pegging the gauge at 260 degrees and the check gauge light goes on. I quickly turn the heaton full blast and the temp will drop pretty rapidly back to normal. While on the freeway, it will do this too. Although I'll turn the heat on again and it will slowly go back down to normal and stay there steady until I get off the exit and start driving around town. As long as I leave the heat on, it will not approach 260 degrees. I'm going to replace the thermostat this weekend, hoping that's the culprit but any other input on this from someone who is more savvy than I on this would be greatly appreciated. Also, if they have hints or info they can share in changing out a thermostat.

Thanks,
Gary Kohlhepp
Gales Ferry, CT

 

tstat sounds like a good start.

 

If it's high mileage, your problem might have been caused by DexCool. Pop the radiator cap and look at it. See if it has "mud" caked all over it. Check your overflow tank and see if it's muddy looking.

Next, use a pressure tester on the cooling system. If the pressure bleeds down, you have a leak somewhere, possibly a bad head gasket causing the overheat.

If the pressure stays up, replace the T-stat and flush/clean the cooling system well. Do it twice if you have to and refill with plain ol Antifreeze. Get rid of the DexCool! DexCool causes the "mud" that can clog t-stats, radiators and heater cores.

 

To hogspeed,
Please do not spread the FUD that has been pounded into everyone on planet earth about the supposed evils of Dexcool. Dexcool does not cause 'mud' or corrosion of any kind. The myths have been dispelled in another thread. I encourage you to read through it and voice your right to an opinion there. To continue to spread FUD (fear, uncertainty and doubt) in someone else's thread is only to incite another discussion such as the one we have already had.

To the original poster,
Do you typically notice this with the A/C on and/or off? How is the level of coolant in the overflow bottle? When was the last time that the cooling system was serviced?

 

Your opinion is noted.

I don't think my opinion is unqualified or based onlack of experience.

Thanks for your comment.

 

Thanks folks,

The coolant bottle is between min and max. It happens with ac on or off. The last time the system was changed was about 1.5 years ago with a complete flush and replenished with dex. It does look muddy, but my mechanic told me it was normal. If you guy have any hints that I might miss with changing the thermostat, please let me know.

This really is a great forum!

 

Sounds like it might be due for a chemical flush. The "mud" thats caked in the rad is more than likely throughout the system so logic tells us if its building up here, its probably worse in the smaller nooks and crannies. This happens withallcoolants (dex or not) in my experience and is normal but you want to get that garbage out of the lines. To do this basically drain the system, put in a good cleaner and run for 3-6 hours as most direct you to, then drain and fill back up with new antifreeze (dex or regular, shouldnt matter after its cleaned).

 

I was a 'mud' victum. I experienced this before I found out that this was a problem with the dexcool stuff.

The overheating issue is kind of like the "What came first, the chicken vs. egg?"question in regard tomy intake manifold gasketleaking. Did the leak develope because it gothot or did it get hot because of the leak in the gasket which caused air to get into the system and turn the dexcool into mud and prevented proper cooling?

After replacing the gasket, my 1999 was still overheating as described above. I did the flush thing, using the Prestone kit, and you should have seen all of the brown stuff in there. Even after the flush, I was still running hot so I ended up replacing the thermostat that I had replaced just 6 months before.

After the replacement, my gauge rides perfectly just below the 210 line (thermostat rated as 195). Sorry, I replaced the dexcool with the old fashion green stuff. It is in the 90's here and my gauge does not go above 195 mark.

 

Buds,

Last Saturday I replaced the stock airbox in my '96 Blazer with an AirRaid 200-108 CAI. Everything installed perfectly, and I definitely saw a performance increase.

Three days later (last night), something in my cooling system blew -- on an Interstate, no less. As soon as I saw my temp gauge in the red zone, I immediately pulled over and shut the engine off. After I towed it home and let it cool overnight, I poured water into the radiator to see where the leak was. It appears to be my water pump. Nothing came out of the hoses. Also, I just got a radiator/thermostat replacement this summer.

Also, it didn't look like the CAI was touching or rubbing against anything, and I know I didn't bump anything during the installation. It was pretty cut and dry. Is it common for a CAI to cause this issue? Thanks for the help.

Raph

 

No, a cold air intake will not cause a water pump to fail, unless you messed with the serp belt.