QuestionI have a 1986 chevy suburban 7.4 (454) with tow package, 373 rear end, 3/4 ton. I just changed the thermostat from 180 deg. to a 160 deg., for the reason that it seamed to run hotter than i thought it should when towing.(I have a 99 coachman that is 6000 pounds on the heavy side)When daily driving it would run around 180 deg.,when towing it was around 230/240 range. After changing thermostats the truck runs around 210 deg. with no load and runs 240 with a load.(it climbs to 240 a lot quicker since i changed this.) Do chevys run hot? Are there different openings on the thermostat for more water flow such as a small mouth or large mouth? My father thinks that the clutch fan isnt working right, does this sound like this could be right? What is your experience on this vehical, how they tow, and how they normaly run temp. wise? Thanks for any and all info and input you may have ! STEVE CHARLES
AnswerHi Steve - Glad to hear you are using a real vehicle to do your towing - there are too many guys trying to pull what you have with minivans!
The 454 does get warm alright. I have one myself and it always runs warm. I do believe that yours is maybe a bit too warm. There could have any one of a million reasons why it is warm, but start with the basics first. Make sure the radiator has been cleaned well. This could mean pulling it out of the truck to be able to spray compressed air or water (be very careful!) through the fins. 15 years of bugs, dirt, fuzz, whatever accumulation could be part of your problem.
Then the flow part of it. Have you done an antifreeze flush on the truck? Go to a shop that has the ability to
power flush the coolant out, not just drain it and refill. There could be a blockage somewhere. Check your water pump, clutch fan, or maybe you just have a bad thermostat. It does occasionally happen.
Some guys pull the thermostat right out, and you may want to try it, just to check what effect it has and to check the thermostat. Do not leave it out, as there is a reason for a thermostat, and the truck will need it. I would suggest trying a GM one if you replace it.
The big old pistons in the 454 pumping up and down produce a tremendous amount of torque. There really is no replacement for displacement, and here is where it shows, trailering.
A couple of things that I do for trailering. I use an external Self-Regulating transmission oil cooler, in the Tru-Cool brand. This is the company that GM uses for factory coolers in their pickups, and the neat thing is they only cool the oil when the tranny gets warm enough to need it. Otherwise the oil bypasses the cooler.
I change the oil in the tranny annually when trailering. Oil is cheap. Trannies are not. I also drop the oil in the rear differential, and refill with full synthetic oil (75W90). More weight on the rear end from a trailer hanging on it, produces more heat in the rear end. Synthetic oil doesn't break down like regular oil does giving you more protection. Then I change this oil every two years.
If at the end of the day, you still have a too hot running truck, drop over on the NewsGroups and talk to the guys on the alt.trucks.chevy, the alt.autos.4x4.chevy-trucks, and rec.auto.tech Groups. Post your question, and you could get repsonses from real-life Chevy fanatics and Technicians who do not mind sharing their knowledge. Use your mail reader to do this, or you can search to see if someone has already asked your question at www.deja.com.
Hopefully this gives you some ideas as to where to do some checking. If I can be of further help, please feel free to drop me a line.
Automotively yours,
Dean
