A some of you may know, I've been chasing an overheating problem on my mostly stock 93 6 speed. I've been through 4 thermostats, 2 radiators, and now 2 water pumps. It's holding, mostly around *205, but will creep up to 212 at lower RPM, but I can cool it off by dropping to a lower gear and holding it above 3000 rpm, which will drop it to 195. I thought I'd post this before I pull the heads and see if anyone has any thoughts. Like I said, it's mostly stock, with the exception of true duals, Flowmaster mufflers and throttle body coolant delete.

 

You only need worry if it goes over 230-240. 205 and 212 are great temps. Unless of course it puking on the ground.

 

Your temps are better then alot of C4 owners have... Why do you keep throwing parts at a motor that's running at the temperture it should run???......WW

 

But it shouldn't be running at those temps while moving at any speed over approx. 35mph.

Sitting at a stop light or in heavy traffic, running in the 220 - 235 range is normal.
But at speed, it should run very close to the thermostat setting (190 - 195 range).

My '96 will stay at 190 - 195 all day long on any road and any gear, as long as it's moving above 35 mph.

 

RollaMo, you nailed it. If mine was doing what yours is , I would be happy, but it's not. Just moments ago, I had the cruise set at 64 MPH, it was running *215. I killed the cruise, dropped it to 3rd gear, held it there (at about 3000 RPM) and it dropped to 201. Never went any cooler than that. I don't claim to be very smart, but even I know that it should not be doing that. It's killing me to know what's causing it to do that.

 

He didn't mention he was above 35 40 mph or at highway speed..It sounds like a restriction in the cooling system or possibly a head gasket ..Im guessing some of the guys on here have already suggested making sure the system is burped properly??...Some of these cars can be a beotch to burp.....WW

 

My 95 runs 185-190° while rolling down the highway..

 

When I cruise both my Analog, and Digital gauge's read about the same, if I lug the engine, climd a hill etc. the Analog gauge (located on Cylinder head) will climd to about half scale.. other wise they "Both" hang out in the 185 ish range..

So one has to "Question" his instrumentation at some point in time.

 

You're not overheating. If anything you're running too cool. If you want power you need to get up into 220-degrees. A lot of race cars are running 240-degrees today. That's about the upper limit.

Here's an article I wrote a few months back about cooling systems.

Richard Newton

 

Rfn, truth is, it's an LT1. Not a race car. As you can see, everyone posting on here is seeing much much lower temps than I'm seeing. My car SHOULD BE running at the lower temps that it was designed (and used) to run. I'm not asking if I have a problem. I KNOW I have a problem. Everything I have done to this car SHOULD have me running around 190* at highway speed. I am running at 215. That needs to be fixed. My question is how do I fix it?? I've spent $1000 on it so far, and it is doing EXACTLY what it was doing $1000 ago. I'm just not going to run an engine that hot. These engines just don't live long at those temps.

 

Desertmike, I have installed new sending units, and the digital and analog gauges are both reading about the same.

 

WW, I've tried EVERY trick in the book to burp it. I'm not getting any air out, so I have to conclude there's none in it.

 

[QUOTE=adtbrown;1585181598]A some of you may know, I've been chasing an overheating problem on my mostly stock 93 6 speed. I've been through 4 thermostats, 2 radiators, and now 2 water pumps.

1. Are you using LT1-4 t-stats, they are different then std. SBC t-stats.







It's holding, mostly around *205, but will creep up to 212 at lower RPM, but I can cool it off by dropping to a lower gear and holding it above 3000 rpm, which will drop it to 195.

2. Is the T-stat a 180 or 160. 180 is factory oem. and because the water runs through the heads first, and then to the block, it will read at least 195 at the sensor. This is the reason the factory LT1 tstat is a 180 yet it will run as hot or hotter then a std sbc with a 195.




I thought I'd post this before I pull the heads and see if anyone has any thoughts. Like I said, it's mostly stock, with the exception of true duals, Flowmaster mufflers and throttle body coolant delete.[/QUOTE]

3. Have you reprogrammed the computer to bring the fans on earlier and again is it the 180 t stat.

I don't believe you will ever get below 195-205 with factory programming and factory t-stat.

 

[QUOTE=rfn026;1585182857] If you want power you need to get up into 220-degrees. A lot of race cars are running 240-degrees today. That's about the upper limit.



How do you figure that? My experience has has always been I make more power the cooler I can get the car before staging. Every tuner I have spoke to recommend using a 160 t-stat to make more power. Go over to the drag racing section and see what everyone uses. If that is not enough, here is a carcraft article saying the same. http://www.carcraft.com/techarticles...t/viewall.html

Again, could you explain how its best to be at 220-240 for most power?

 

Whats wrong with that?
Those are good numbers..better than most.

You have to learn to STOP thinking 'old school' when cars ran at 180.; C4's DO NOT and it is NOT good to try to make them run that cold...
There are a doz great reasons why it should run at 200 to 225 in ambient temps of 90* with the a/c on.

You have nothing to worry about. I would be far more concerned if mine tried to stay under 200 on an avg day.

 

If it were a head gasket, increasing the RPM would make it worse, not better.

There is no coolant loss?

Are you certain about VAC leaks?

even with the variations you describe, there is still not any extreme temps. Head gaskets will send the temps thru the roof if its eating the water or it will pressurized the system and force all the water out the overflow tank. The temps come from the loss of coolant. If there is water getting in a cyl there will be a spark plug that looks steak cleaned....very different from the rest.. That is, IF you have coolant loss.

2 things have to happen. Water HAS to circulate freely. Air has to pass over the condenser to remove heat from the water.

That's it.
You MAY have to do some trial & error research. I would remove the T-stat and drive it like that for a few days and see how it behaves. Look in the filler and watch the water FLOWING thru the core. Look for bubbles, surges, note the water level as the engine revs and decelerates.

You may be seeing temps go up from the engine lugging slightly. The more it struggles the hotter it will get. Dropping down a gear puts it in a better power range....again, more rpm generates more heat and with a bad gasket, a worsening of the symptoms, not an improvement.

You have checked the gauge for accuracy? infra-red sensor to confirm? any other significant SES codes?

I had a similar cooling issue a few months ago that was causing all kinds of bizarre symptoms, AND coolant loss. Nothing seemed to be wrong. I took **** apart, put it together again. I started to conjure up the dumbest theories you can imagine to "make" a problem that I could comprehend...I had half these guys thinking about it as well.

Turned out to be a PIN HOLE in a very short heater hose under the a/c compressor. It never leaked a drop....too small. But it did spray a very fine mist toward the #2 exhaust where I can assume it was instantly vaporized without leaving ANY trace of coolant. I was getting NO circulation from the pump at times....this was explained later. As the mist voided the cooling system when it was shut down, the pump cavity was emptied and the surrounding hoses as well. Next start up the pump would be turning dry...no coolant anywhere close. With a closed T-stat the water could not self-level as you think it would.
Simple problem. Even easier solution. Damn difficult to diagnose mostly because I was OVER-THINKING the whole issue...
A pin hole in a hose....I was shopping for short blocks and rebuild kits because I was SURE it was a head gasket and/or some seriously damaged hard parts.

 

Who were these 'people'.....and what evidence/documentation did they provide to back up these 'claims'?


What happens in the 210* range that optimizes power/performance/reliability? Where's your data to support this claim? Where's the beef?

Why is this?

Yeah.....I agree that heat is a good thing. If your goal is to go around, warping heads.....

KW

 

The information came from Joe Gibbs and the Hendricks people. They really don't want to share their dyno sheets. The do know about making horsepower though.

The radiator people I spoke with are DeWitt and C and R Racing. C and R has shop in small town in North Carolina. It's called Mooresville. There are a few race shops in that little town.

Seriously though the world has changed. I went back and checked my data sheets. I normally run about 210 water and 250 oil temps at both Sebring and Homestead. Both will get a little higher if I'm at the limit for a few laps. No big deal though.

The short track guys are the ones that run 240 degrees. As I said that's pushing the envelope.

Richard Newton

 

Race cars with race car type intakes that are seperated from the engine heat and air intake systems that are seperated from the engine heat with race fuel that will not detonate may make more power with high water temperatures. Street LT1 corvettes that have intakes heated by the oil and water, intake air heated by the underhood heat and street fuel that will detonate will not make more power being run at 240 degrees. Every car I run on the dyno makes the more power when it is run under 200 degrees with street fuel. Truthfully most of them make best power in the 160 degree range.

 

With the lack of cooling flow idea. As you rev the engine up you increase the water pump speed which will increase the speed that the water flows through the engine. Depending on where the temperature readout is located this could cause a decrease in the gauge reading since the water in the engine is moving faster it may not have as much time to pick-up heat which may show a reduction in temperature on the gauge. (I am not saying that the actual temperature of the engine is any different what I am saying is the gauge may be located in a spot that is effected by flow. The actual heat rejection of the engine to the air may still be the same)