Just bought 65 396. Car runs 210 degrees highway and up to 220 at idle.
Any history of these cars having overheating problems. I understand this car has highflow waterpump. It has 411 rear end. Could high rpm's be causing pump to turn too fast? Car has new Harrison aluminum radiator so I'm thinking this part is okay. Will check thermostat and guages this morn. Any suggestions appreciated!

 

I have the same car with same RR.
Tossed my thermostat after trying a few things.
Went from 210-220 to 170-190.
I also am running no fan clutch.
Direct drive fan.
Many here will say "don't do it"
But it worked for me.
The car runs great and never rises above 200.
Not even in stop and go fwy traffic.

 

...back to basics...how do you know your gauges read true?...that's the first place to start......a number of additional questions before you spend big bucks....btw, those temperatures are OK for a big block.....are you running a 50/50 mix? - water in reasonable temperatures (with pump additive and water wetter) will cool it down a bit.....direct drive fan is the way to go imho..which tstat are you running?....most recommendations are for 180 but i'm OK with a 160 for anything but the coldest mid-atlantic days...lots of little stuff to do first, like make sure there are no huge holes in the radiator shroud....how do you know your fan clutch works, etc....post what ya got :yesnod:


..just note that i also tossed the tstat for a while but recommend that you do run with a tstat of your choice as this increases engine efficiency pretty dramatically and helps ensure that the fuel atomizes right from the start


[Modified by Kid_Again, 6:24 PM 2/25/2002]

 

Thanks for info. I checked gauge this morn and it reads 20 degrees hot so I have ordered sending unit plus 160 degree thermostat. May have to repair gauge itself. Gets hot in Texas so the 160 may not work? Is anyone giving a reason when they say don't do the direct drive fan? Bear with me as I am new to all this!

 

Checked gauges today--read 20 degrees hot. Ordered sending unit and 160 degree thermostat. Don't know ratio of water to coolant but will replace to correct mixture when I replace thermostat. Car has new Harrison aluminum radiator but I don't recall a shroud. Will check. Have been told fan clutch okay but may need to try direct drive. Thanks for the help!

 

You can check the operating temp with a IR Temp gauge. My 396 runs between 190 and 200 on very hot days with basically a stock setup. I have recalibrated the stock sending unit and it indicates only a few dgrees variance from the IR temp unit. I am not sure if the 160 thermostat will buy you anything. The direct drive fan is a good way to go if you do alot of bumper to bumper stuff. Before I checked the sending unit it would routinely run 210 to 220 but never belch any water.

I use 50/50 mix of water and antifreeze. Changed all the hoses. So far so good. You might also check your timing. Improper timing can cause an overheat as well.

Good Luck.

Chris

 

Unless its puking coolant out the overflow, I wouldn't sweat it. These mid year big blocks run hot because the radiator capacity is marginal. Thats why the solid lifter big blocks weren't available with ac or automatics.

 

...nah, no reason not to go to a direct drive fan, 'though it will be noisier (i have pipes on both, could care less)....you can go with a flex fan in addition but i kept the stock fan on the big block, pulled the rain guards on the hood grill and it ran just fine...you need a tstat to rapidly get up to operatng temperature...duke ( a forum resident guru) really recommends a 180 and you can't go wrong with his advice.....

...btw, your gauge may be fine if it reads too high - there's a resistance mismatch between the old gauges and new sending units - i added a $0.25 resistor to the temp sender wire (will post the specs if i can find it - others here will know) and brought the gauge pretty much in line......remember, these old analog gauges are not linear over their range so these are to be considered like romans consider red stop lights - "for advice only" :D

..if you have a new radiator (brass is fine, don't worry about aluminum) and you've flushed the system well and taken care of the basics - just drive it but keep an ear out for detonation just in case

good luck :cheers:

btw..the resistor that worked for me is 1/2watt, 22 ohm


[Modified by Kid_Again, 2:23 PM 2/26/2002]

 

When you get your new sending unit, your gauge will still be off, and will need to be calibrated with an I.R. gun and resistors to read properly at normal operating temperature; the sending units AutoZone sells seem to be closer to correct calibration than any of the others. If you don't want to go through the exercise with the resistors, just compare an I.R. gun reading of the thermostat housing with what the gauge says, and understand what the gauge is really telling you.

You NEED a thermostat to permit fast warmup and to properly regulate coolant flow, and to maintain proper engine temp if you drive in cold weather; 180 is the one to use.

Basics - only two things determine cooling system performance - radiator efficiency and airflow through it. If you have a new correctly-sized Harrison radiator, that side of the equation should be OK. For the airflow side, the radiator needs to be sealed to the rad support so all the incoming air is forced through the radiator and not allowed to go around it (Dr. Rebuild has the best radiator seal kits), and you need the proper shroud with the fan blades half-in and half-out of the shroud for in-town cooling performance.

Another frequently overlooked potential problem is the lower radiator hose; it has an internal wire spring that keeps it from collapsing at highway rpm (due to suction from the water pump) that can corrode away over time - it can be fine at idle, but collapse at highway speed and restrict coolant flow.