I own a '93 LT1 that is intent on overheating. I changed the thermostat and I had no success. Are the secondary fans supposed to kick in autmatically when the vehicle starts to get warm? If not, what could the trouble(s) be? I have been told that the switch for the fans might be bad. I have also thought that maybe the heater core went south or perhaps the water pump. Before I take it into my $100 an hour Chevy dealer, what can I do to either find out or eliminate what is wrong? I saw water pump prices and I got ill. The heater core was a less expensive item but there is a lot of labor involved in both repairs. If anybody has some answers, I would greatly appreciate them. Thank you in adavance for your help.

Bob

 

You need to pull the shroud off of the radiator, pull it out and clean thoroughly. This happens because road dirt gets sucked into the fins from the air dam. This will solve your problem.

 

OK, what exactly do you mean overheat? How hot are you talking about? Are you reading the temp from the digital gauge or the analog? The experts say that you shouldn't worry until the temp gets up around 250-255*.

Be aware that LT-1 engines were designed to run warmer than a typical SBC. I believe that the primary fan comes on something like 215* and the secondary will come on at 238* (IIRC). Or if you turn on the AC they will both come on. They run hotter than I was use to. My 99 Silverado and my 03 Bonneville run at about 200. The Corvette (94) will run 195-220. Used to freak me out, but not any more.

 

I guess if you're running higher than the temps above you better check out the radiator, our c4's are like vacuum sweepers sucking up all kinds of junk and it will deposit it between the radiator and the AC condenser. Like suggested above pull the radiator out and clean in there. Some guys have changed out the stock radiator for "Be Cool" or "DeWitts" (these guys are a forum sponsor, check out left side of the main window).

 

Usually does, also you need to pull as in take the radiator out. shoot it with air while it is dry then pressure wash it to blast the crud out, shoot it close with the pressure washer. you will be amaized at how much dirt falls out. this stuff acts like a blanket and keeps air from flowing through the radiator. also make sure no bolts fell out of your fans which would let them sit in there cocked. or you could buy a brand new unit from corvette recycling here on the forum for $99 bucks.

 

Not to sound dumb but I have never seen such a complicated mess in my life when I open the clam. My '69 was a piece of cake compared to this. So far I changed the thermostat just in case the one I had was no good. That yielded no change. I then went and changed radiator caps but do not know how to "burp" the system just in case there might be a bubble in the system. The vehicle is making me feel stupid.

How in the world, without taking apart just about everything, can you get the shroud off? I am so used to older cars. In some of those land yachts of the '60s you could practically sleep next to the motor.

Bob

:o

 

Can you give details on your overheating situation like temp it reaches, how rapidly it climbs, etc.?

 

I start the car. It takes about 10-15 minutes, while idling, to get to what was normal operating temp. After that it starts to climb and in about 4-5 minutes it is between the halfway mark on the gauge and that three quarter point. At that point I either turn the car off or I put on the heater or AC. The temp starts to drop but does not get back to the "safe" spot I was at before. The radiator is filled with green. Could it be the heater core or the water pump? I think the pump is okay because there is no pool of water under the car. I smell antifreeze in the car so i leaning to the core but I am more than a novice these days.

Thanks for all your advice. I know someone will figure it out. I know I can't.

Thanks,
Bob

 

Does the '93 have a digital temp gauge? If so, what is the reading?
Haveway to three quarter on the analog gauge is completely normal, and in fact while sitting in traffic the analog gauge will get all the way over to the high end. Look close and you will see a "shaded" area on the gauge, and the needle should be just shy of the shaded area.

These cars run hotter than any Chevy you've ever had. They were designed that way by the engineers. GM says to shut it off if it gets to 260.

Normal

Not sure the heater core has anything to do with what you might think is overheating. But if you smell antifreeze in the car, you very well could have a heater core leaking. Check the passenger side floor under the carpet for wetness.

 

you can pull temp on the climate control...now i just have to remember how i did it before LOL. my car was doing the same thing a few weeks ago, i was convinced i needed a big ole king kong 321 core racing radiator. then one of my friends yak'd at me to clean the stock one. i did and a pile of dirt and gravel came out, put it back in and it runs fine. i also have a .040 punched block that runs 12.4s in the 1/4 mile. it now runs fine with the stock radiator. burping these is easy, you fill it as much as you can, drive till you get to operation temp, let it cool and fill the rest of the way. pulling it out is also easy, just start unhooking stuff, other than the 3 7mm bolts down each side everything else is right in front of you.

 

The temp on the digital gauge reads low, like 140 but ironically prior to this problem, the digital temp always read high, like 210-221. Now the reverse is true. My guess is that my problem is the heater core. If it is, how hard of a job is it to replace the core? Is it easier than the cores of yesteryear to replace when you just about had to remove the entire dash? I read somewhere that only a piece of the dash is removed, making it significantly easier to replace these days. Has anyone ever done this on a C4 model? Please reply with any info, if you know.

Thank you,
Bob

 

Bob, I have not done the heater core.....but from what has been posted in the past about this job, it's one of the worst to do. I too have read about some who have done it without removing the dash, but that was with the earlier models 89 and older (IIRC). If you use the search button there has been a lot of posts about this subject.

 

Before buying more parts (and unless you smell coolant inside the car or the passengers side carpet is wet, you do not need a new heater core), check for dirt and debris in the front of the radiator and A/C condensor. If you look up behind the front license plate, you can see if there is junk up there.

Using a garden hose, direct a stream of water from the fan side of the radiator so that the water pushes out the dirt. You can spray the fins with some Simple Green and let it sit for a few minutes first. Chances are that you will get a bunch of junk out from between the fins.

As mentioned, later C4's are designed to run hotter than early cars. Higher heat helps to reduce emissions and it's typical in most all newer cars. With the stock 190 degree stat, you should expect to see temps of 190 to 210 while cruising and the temps can go higher in stop and go traffic.

The secondary fan will come on at around 228 degrees and shut off when the temps drop. So seeing 210-220 temps can be "normal".

Keep the digital gauge display on coolant temp to watch for temp changes. The analog gauge is not linear in its display. As the needle moves toward the high number side, it takes less movement to record a wider temp range.

The LTx motors use two different temp sensors for the two gauges. One sensor is for tha analog gauge and another is for the digital dispaly and fan relay input. Once coolant temps go beyond 140, the digital display shoud show a fairly accurate reading of coolant temps. From you r description of the display values, you may need a new sensor. It's the one on the wter pump.

Do the cleaning and watch the digital temp values and report what you see. You can check for fan operation by running the A/C as that will force the secondary fan to run.

Hold off on buying more replacement parts until you do the cleaning.

 

Your heat problem may be as simple as a blocked radiator. c4cruiser gave some excellent advice. Simple Green does a great job in cleaning the radiator. Hosing out the air intake area should help dramatically.

It is important to note the engine does run at higher temps, as compared to other cars. The fans turn on at higher temps as well, except when the a/c is turned on.

 

I have a 87 and when I am sitting idle it will go from 186 to 220 in a matter of minutes. What temp reading in the digital readout is time to be concerned about overheating.

 

Take it from me.....I have a 93 LT1 with the same problem as you. I pulled the radiator and pressure washed it for 1/2 hour until all gunk was removed from in between fins and she runs in the 190's now. It is amazing the difference it made and the only way to clean it is by pulling it. Good luck!!!!