Gents,

Looking for a little advice on a overheating condition that I have recently been experiencing.

I have had my for a little over 2 years and ever since taking delivery I have not trusted the temp gauge. While observing my temp gauge it pegs out very quickly. Since all this has started I have changed the thermostat twice , sending unit numerous times, water pump once and finally taken the thermostat completely out. I currently have a direct read radiator cap and have brought home a Infrared Gun to shoot the temps. When shooting the temps I have shot at the cap, directly to the sensor and the themostat housing. The readings have always been consitent around the 180-200 range and the cap has said the same thing.

Today I took it out for a little spin and by the time I got home the temp gauge was reading 260 and beyond. Knowing that I do not trust the gauge I opened the hood and verified from the cap and they both matched. I actually observed boil over into the recovery tank also.

Now a little about the car and engine. It has a 350 with 9.5-1 compression with Brodix aluminum heads. The valve train and cam is Lunati set-up 280/280 with 540/540 and with full roller on the top side. I also have a 5 blade flex fan drawing air through a 4 core aluminum radiator. The fan resides about 1" inside the shroud and has the max spacer installed. I do not have AC. The car is missing the lower spoiler to push air into the radiator though. I llive in VA and the weather is currently in the low 80's.

Knowing all that I have stated is it believed that I could possibly have a clogged or bad heater core. There has never been a leak observed during all the time that I have owned the car. When the water pump was changed the Anti-Freeze was also changed to Prestones new 50/50 mix.

If it is the heater core, what all is entailed in the R/I process. I would assume it comes out under the dash?

 

typical overheating factors
Radiator seals-missing or not sealing
lower spoiler
lean carb mixture
retarted timing
bad fan clutch
clogged coolant system.

 

I see no actual signs that it's overheating. If you put black tape over the gauge so that you can't see the reading, does the problem go away?

I can guarantee that it's not the heater core. It is normal for a small amount of coolant to flow to the coolant recovery tank. That's what it's there for.

Most probably you have a farqued temperature sender in the driver's side cylinder head.

 

I have too much money invested in motor too not worry about the temp. I do not have a temp sending unit in BRODIX aluminum heads my unit is installed on the intake next to the thermostat housing. When I first meaured temps with the I/R gun they were consistent with the direct read cap. I would be willing to tape over the gauge if you are willing to pay the price for a set of Aluminum heads.

 

I am def inconcurrence with clogged cooling sys. I run rich on the carb side and do not have a fan clutch so we can eliminate both those. Fan seals questionable, but since I have had it for two years and the temps have been pretty consistent throughout this time frame I would tend to rule out the spoiler and seals since I drive it on occassion in summer in much higher temps and do not see an issue. I believe clog could be the problem as you stated. I will pull off heater hoses going to core and will try to flush that first with low pressure. The radiator is failry new and each time I have looked at I did not see any build up in the cells.

 

Just so you don't go on another wild goose chase, many Corvette owners block off the heater core, or rely on the factory installed shutoff valve. A blocked heater core will not cause your engine temp to increase.

I'm confused about correlation of the rad cap and the IR gun indications. Do they always read the same? If so, what makes you think that there's actually any overheating going on?

 

When I first noticed the Gauge problem was right after I bought the car. From this point is where I swapped out the sending unit x2, thermostat x2 and finally removed t-stat completely. I purchased the direct read cap and brought the I/R gun home from work and verified temp at the 3 listed locations in past message. Since the cap , sending unit and t-stat housing were all reading the same I was satisfied that I was not running hot. Today for some odd reason it smelled warm when I pulled into the driveway. So I proceeded to open hood and verify cap temp, it was sitting @ 260 and climbing after I shut-down. This is when I noticed boiling flow back into the rtn tank also. I have never seen this happen before on this car. I did notice a very very slight bubbling around the valve that lies between heater core and radiator. Can this valve cause a overheat condition?

 

What are the symtoms? On the freeway, you have sufficient airflow across radiator. It it runs hot at freeway speeds suspect radiator size / efficiency. If it runs hot around town and climbs at stoplights, suspect airflow. By the way, a good thermo clutch and AC steel (7 blade I think) has always worked for me. This assumes good pump, etc.

 

That valve's only purpose in life is to shut coolant off and keep it from circulating thru the heater core.

Temperature climbing after shutdown is not uncommon- water pump is no turning, coolant not moving, heat soaks in.

I'm not a fan of removing a T'stat. No restriction in the system, the water has no time to pickup any heat that would be transferred. Just my opinion. I'm sure there are people that will swear that will keep an engine cool.

DO your IR gun readings and your gauge match? I might have missed that in a previous post. And have you made sure your radiator seals are intact? I used that 2" pipe insulation down both sides of the radiator and then a foam swimming pool snake across the top. Works great, even if it is a bit Bubba.

 

Put the thermostat back. Taking it out will cause a bunch of other problems (like not warming the engine to the right temp) even though that's not your problem now. As long as the thermostat is not stuck in the closed position, it won't be causing your problem.

Second get rid of that flex fan junk. They don't work as well as the original set up. Someone had put one of those in mine and I was having all sorts of problems even with a Griffin aluminum radiator. As soon as I went back to a stock fan and clutch, I've never had a problem.

Finally make sure as others have said that all the seals between the fan cowl (you have one of these right?) and the radiator are in place, there should be no where were the fan could pull air other than through the radiator.

 

and Ditto on the swimming pool snake

 

I have seen replies from yourself and one other that talks about putting the 7 blade fan and original fan clutch back on; with my engine it will take away from horsepower? My car has never been on the freeway and all the driving is done in town. With that said Airflow is a factor and not having the lowerspoiler and posibilty of missing seals could be the problem. The odd part of this is that when I drove it around during the hotter summer momths I never experienced this problem. Now that it is Fall and the temp have gone down is when I experienced my first over-heating event. I am on my way to Lowes to get the seal material.

 

Where did you get the temp sending sensor? The generic auto part store units are not calibrated correctly for the gauge. Get one from one of the vendors here - Willcox or Zip. BTDT.

 

How old is the lower radiator hose? If the internal spring has rusted, it could be allowing the hose to partially collapse.
If you just let the car sit and idle for 10 - 15 minutes, does the temp creep up?
Automatic or standard?

 

The hose is the original one that came with the car when I bought it . It cannot hurt me to change the lower hose though. The temp on the car will creep up w/o any problems while sitting in the driveway idling. I can watch the direct read gauge and it will climb failry quickly. So the lower hose and the radiator seals will be the first test. I am also getting ready to install the lower spoiler, it has been missing since I bought it.

 

Well you can't say you didn't get your moneys worth out of the hose.

Unfortunately, unless you can see that lower hose collapsing at an idle, that's not the problem of the temperature creeping up at idle. Usually the draw or suction from the water pump makes it collapse at a higher speed.

 

I have pics of the engine bay if anybody can help me post them

 

http://photos.imageevent.com/durango...g%20Images.pdf

This is a good tutorial put together by a member.

 

http://s355.photobucket.com/albums/r441/bumpervetteman