TowShen

i need some help......after about 2-300 miles of highway driving the engine starts to over heat, and keeps over heating in like 3-4 mins. but when i just do local driving there are no problems......plz help me!!!!!

imnotplutonium

iTrader: (4)

maybe your pcm values are messed up. if you can, try to look at them. have you had a tune?

Steve40th

Doesnt the ECT sensor in the water pump also tell the PCM/ECM what the temp is to ensure that it knows when to turn the fans on?

imnotplutonium

iTrader: (4)

right but if the values for high speed are too high then they wont turn on until they hit that value. so if for some reason his are like over 210-235 or something like that it could cause his car to overheat on the highway where the mph is high enough to change the values for the fans to high speed temp values.

Steve40th

Okay, But I was thinking trouble shoot the simple stuff first before going elsewhere.

93formulabird

iTrader: (2)

If highways driving is making your overheat its most likely a water pump problem or a tstat stuck closed, since there is plenty of cool air and you dont need fans on the highway.

Easiest thing to do is replace the t-stat first.

emj2006

iTrader: (5)

check your cooling system. Do your fans turn on? Check if the fans turn on after it reaches the maximum temperature(depending on what temperature your fans turn on). Check if theres enough coolant, check the water pump, check for any possible leaks, thermostat. I had a water pump failure which caused my car to overheat and got it fixed.

infinitebird

iTrader: (11)

In the stock tune there is no distinction between high and low speed temp values. The MPH threshold is set to 0. High/low speed only matters if you've activated that yourself in a tune.

imnotplutonium

iTrader: (4)

mine was set to 30 stock. and i guess it does sound more like the thermostat or water pump since there is plenty of air at high speeds.

the_merv

iTrader: (88)

I would check the thermostat first.

TowShen

i have the electric cooling fans on togle switches....

TowShen

took out the stat. and was still having over heating

urbanhunter44

iTrader: (1)

Is there lots of water near the weephole on the pump? Have you flushed the coolant recently? After letting your car warm up to operating temperature, are both the top and bottom radiator hoses very hot and the same temperature?

infinitebird

iTrader: (11)

No offense man, but I have tuned a lot of LT1 cars and have never seen that. That is not the stock value.

Taking what you just said there and this thread into consideration, I find it incredibly difficult to believe you are working with a stock pcm.

imnotplutonium

iTrader: (4)

i understand where you are coming from. I had my old pcm tuned. it crapped out so I had to buy a brand new one. that is why i was having problems with cooling myself in that thread. I also had problems with the speedo because when messing around with tunercats for the first time I f'ed up all the values. so I had to change them back to stock to work. when I got my first data file from the pcm the low/high speed value was set to 30 and I changed it myself to 40. that is just what I saw. Maybe it wasnt totally brand new. just trying to help out from what i've experienced

93formulabird

iTrader: (2)

Guys fans do not have anything to do w/ it. If it overheats on the highway. come on.

TowShen

no leaks
yes i have flushed it
YES both hoses are HOT!

burnzilla

iTrader: (3)

Waterpump, or the waterpump gasket.
Odds are if they replaced the opti, they replaced the gasket. You have too, when you do that much work to it.
IMO, its in that area. Could be a faulty thermostat, but I wouldnt get your hopes up.
Check for burnt wires, and possible coolant leaks.
Make sure your fans are workin too.

Hint:
In crowded situations, turn the A/C, even if you dont have any.
It will tell the PCM to enable the fans. Its one of those little tricks.

Good Luck