overheating Chev 3500

Mingay · January 29, 2007

hey guys, i have a 1988 Chev 454 3500, its Supercharged with a Vortech charger. i have twin 16inch thermo fans, and new radiator core. i even have a undertray under the engine.

When im towing my 7500lbs trailer it gets so so hot. it goes well past 240degrees with light going on and staying on for ages when i go over mountains, and i got no more tricks up my sleeve to keep it cool? it is summer over here in Australia so its a bit hot but it still gets way too hot.

it cruises on flat highway at about 210-220 degrees while towing and 200 when not towing.

what other things can i do to prevent it from overheating?

Being in Australia no body knows much about the mighty chev's.

its also got 130,000 miles on clock.

thanks guys your help is appreciated

95Sierra2500 · January 29, 2007

Did you put in a LARGER radiator when you put in a new core? I would recommend going with a lower-temp thermostat (probably around a 180) and then start looking at ways to remove heat from the engine bay. Perhaps you need an intercooler between your blower and the engine? I know that blower is making ALOT of heat. Headers may also help get heat out of the engine bay, if you don't already have them. Header wrap would also probably help some. You may also want to check to make sure you're getting plenty of airflow TO the radiator (you can have the biggest fans in the world and without air getting to the radiator, they're useless). The last thing I would consider would be putting some kind of heat extractors (functional ones) on your hood to help draw out the heat. I don't know if that's really an option for you or not.

I'm presuming that the truck is an automatic, which naturally adds heat because of the transmission cooler. If you had a manual alot of your problems would go away as the transmission would not be adding all that extra heat.

Rolandd · January 29, 2007

I would check the basics on the engine to make sure that it is running within spec: timing and air/fuel ratio. With the miles you have on this vehicle the timing chain could be stretched, altering your ignition timing. With the blower, you could be masking a lean fuel ratio condition that could lead to the overheating. I guess the other question is has this setup behaved properly in the past and is only now giving you issues or have you always had problems with the current configuration.

If all of the above checks out then you need to find ways to remove heat from the engine and other components. As suggested above, an intercooler may help, as well as additional tranny and oil cooling.

I am curious if the fans may be contributing to your problem at highway speeds by slowing the airflow through the radiator(s). Just a thought, but make sure that they are pushing air the correct way (towards the engine block). It is too easy to check this no to: just stick your hand in front of the radiator and behind the fans and feel for the breeze. If they are wired backwards or installed on the opposite side of the radiator from what they are designed for you can create this condition by accident. I have seen it before, along with a lot of hard time and money spent solving other non-problems to no avail. Under non-loaded conditions your are driving faster and the fans may not come on whereas when towing you are moving more slowly and generating more heat--the fans come one and push air through the radiator the wrong way aggravating your issues.

I would respectfully disagree about the thermostat. The computer needs the correct thermostat because it uses coolant temp to set the air/fuel mixture. If you have a low temp t-stat, the computer will never get out of warmup mode yielding lousy economy and reaking havoc for your cat converters.

ZZebes · January 29, 2007

Try getting rid of the undertray and that will let the bay breather, cause you culd have the biggest radiator in the world and hurrican force winds and if the air can get out of the engine bay all you are doing is increasing pressure internally and creating a pressure cooker.

95Sierra2500 · January 29, 2007

As old as his truck is, he should have NO problems with a lower temp thermostat. My dad runs a 180 in his '94 1-ton with a 454 and has suffered no mileage loss. After running it since about 140k miles (he's up to 260k now), his cat is FINALLY going bad. However, Michigan allows vehicles that old with a GVWR over 10k lbs to run without a catalytic converter, so he may not replace it but just remove it. It's also AFTER the muffler to keep the exhaust gases from cooking the cat...454s run HOT and the exhaust manifolds will turn blue and red when towing.

Mingay · January 30, 2007

thanks for your imput guys, its the most constructive responses ive had in 9 months of asking mechanics here in Oz.

My 454 has new double row timing chain, Cam, Barrell Intercooler, has been on Dyno and computer rechipped, aditional 2 injectors with piggy back computer. has Headers and 2.5inch exhaust system with no Cats. i have a small scoop on bonnet to extract hot air.

I have tried it with and without undertray and seems to run a wee bit cooler with it on.

It is an Auto so has tranny cooler in front. The Thermos are DEFINATELY running in correct direction. It has a larger than normal radiator core. It still has Aircon core in front of Rad, maybe i should remove that??

What temps do they normally run at? and what temp can i safely run it at for long trips?

thanks guys you rock!

95Sierra2500 · January 30, 2007

My dad's truck runs about 180-190 empty, around 200-210 pulling their 42 foot fifth wheel with a 180 degree thermostat. The only thing I can suggest at this point is that perhaps your coolant is breaking down and can't carry the heat away like it should. You may need a coolant flush/refill, depending on when the last time you had it done was. The mixture of your coolant could be off as well. I really have no idea since you've done about everything I would do to combat this problem.