Hello. This is my first post on corvetteforum.com. I recently picked up a 1996 Corvette LT4 for $11,500 w/ approx. 97,000 miles. I've inspected the whole car and everything is in working order with the exception of the cooling system.

Dilema: After pickup up my car, I went on a 40mi. trip back home with the A/C on. I was at a stop light and noticed the engine temp went up to 227 degrees. Once I got home, I noticed a "gurgling" sound coming from the upper coolant resevoir.

Could this all possibly be just a aged thermostat with air pockets in the cooling system? Please help with any suggestions. Thanks in advance.

 

That is not a bad temp for a LT4. When my 86 gets to about 225 and I shut it off you can hear coolant gurgling into the resevoir. I have no leaks and it runs at normal temps driving and up to 230 at idle before the fan kicks on and down it goes.

 

Good job picking up the best C4 (excluding the ZR-1) as far as I'm concerned.

227 isn't THAT bad at a stop, it might be bit high. I had the same sort of symptoms when I got mine.

I cleaned the debris from the condenser and radiator, drained the system, installed a fresh 180 thermostat, then filled back up with new 50/50 Dex-Cool.

All that lowered my temps about 10 degrees across the gammut of driving conditions.

There's other things to consider but I'd lay money you're condenser is clogged with road debris as well as the radiator. A coolant change with thermostat can't hurt either.

I think folks are fooling themselves thinking they're getting theirs clean without removing the whole radiator and condenser from the car. Mine looked OK after just sucking the crap away but when I took them out you couldn't even hardly see through them they were so packed with muck.

A Simple Green soaking front and back and light power washing did the trick for me. After that you could see light through them without even holding them up to the Sun.

BTW, if you go and change the T-stat get one with an air bleed, makes filling it back up a no brainer.

 

Was 227 the max temp you saw? If so there is nothing to worry about, that is within the acceptable range, and it means that your fans were able to keep the temps within that range. You really only need to be concerned when you see 235+, and start to get worried and pull over when you see 240+

 

I'd pop for a new rad. cap as well. If your at 227 when you shut it off, the temp's going to climb from there due to the lack of coolant circulation, and if temp ^, then Press.^, probably enough to lift the cap and relive to the resivour (hence the bubbling you hear).

 

As you are new I will say somethings you might/might not have heard.

First and foremost do not wash the front of the motor where the opti-spark distributor is (under the water pump). A water soaking can destroy an opti-spark, even the newer GenII on your 96.

Enigine cooling fans are factory set to come on at 227-228 for the main fan and 236-237 for the auxillary fan. But if you had the A/C on the main fan should have been on all the time.

To purge air out of the cooling system you have to use the bleeder screw. Look on passenger side by the throttle body for the little slotted brass screw head.

Check with flashlight thru passenger side opening in the radiator shroud for debris in there, also from underneath for front of condensor. all the cooling air is sucked up from the bottom like a giant road vac and you might be amazed at the crud sucked in there. Unlike others I don;t pull my radiator, I just made up a long tube adapter on my shop vac and very carefully move it around in there and suck the crud out. At somepoint if I see a problem developing I will pull it, but not yet.

Hope this helps, You Got a Great Vette!!! Congrats!!!

 

The high temps where engineered into the engine for emission test purposes. I've found that the LT4 , like most engines, runs much better when the temp is below 200. I'd suggest going with a 160 degree thermostat (Hypertech sells a good one) and clean the radiator as many have suggested above. DON'T GET THE OPTISPARK WET!!! Also, think about adding a bottle of Water Wetter to the coolant mix. I try to run 60 percent distilled water and 40 percent Dex-Cool.

When you drain the coolant - especially if you drain the block too - you'll find that the LT4 has lots of places where air is captured. You'll have to start the engine and let it get hot enough to open the thermostat two or three times to "burp" all of the air out of the colling system. Each time you'll be adding anywhere from a cup to a quart of coolant-water mix. The bleeder valve on the thermostat housing is helpful, but it won't get all of the air out of the system. Don't forget to clean and refill the overflow reservoir, which is way down in the front of the car below the right headlight. The "hot" and "cold" levels are noted on the dipstick for the reservoir.

Also, the digital temperature on the dash display and the analog temperature guage get their readings from different locations (the water pump and right-side of the block, respectively), so don't be surprised if the readings are very different. This will especially be true before all of the air is out of the block.

 

If the cooling system has to be topped off every few days or so, it could be a small head gasket leak, keep an eye on the coolant levels.

If the cooling system hasn't been maintained recently, I would do a complete flush and fill and install a new radiator cap and stock heat range thermostat.