well, after finally getting my new oil pump n screen on, n putting the pan back on this weekend, it was time to address the overheating issue. I put a 160 deg. thermostat in it, cleaned out the radiator and put new coolant in. But it still runs ataround 205 deg. while driving 50 mph. , which is wayy to hot. If i sit at idle it will jump up to around 220, and after i shut it off it will rise to close to 230. Im not afraid to shell out the 200 bucks for a new radiator, but i just wanted to make sure i wasnt overlooking anything before i did.Does a water pumpjust go bad atonce, orcan it slowly lose its performance?Let me know your thoughts guys. 1968 coupe, 289, C4 tranny.

 

205 isnt bad if you were running a 180 thermostat which is common.

Really it doesnt sound that bad. what would happen at 80 mph on a 100F day?

You can flow test the rad with some water pour a half gallon in the top and it should flow out the bottom after a about 3 or 4 seconds and it should have good volume to it.

Check the cooling fins on the rad make sure they are no packed with dust, you should be able to see clearly thought them.

Finally a water pump will almost always work up to the day where it starts to make noise then its a matter of a few hours. You can grab the pulley and flex it up and down. If you detect any play then its about had.

Gun

 

when you say you cleaned out the rad do you mean you stuck a hose in it and flushed or took it to a rad shop, tanks off and cores cleaned? You need to do the same thing with the heater core.

Flushing it with a hose dont cut the mustard

Also make sure you didnt get an airlock...is the rad still full of water?

+1 on the water pump, but they can lose efficiency before the bearing fails. +1 on making sure the fins are clean externally.

The jump up in temp after you shut it down is normal

 

so, how do i tell if i have air lock or not? I filled up the radiator, ran it for a while, and the water level in the radiator never dropped any at all. So if i have air in the system, what is the best way to burp it out? So running 205-210 isnt that hot? I was under the impression that a 160 deg. thermostat, would keep the running temp. in that area, maybe im wrong.

 

Well if everything was working perfect then the 160 thermostat would give you an operating temp close to 180 to 200. The thermostat just starts to crack open at 160 and probably isnt fully open until 180ish. 205 to 220 isnt way hot but 220 is a bit above normal.

if you have water in the top hose and the bottom hose and drove the car bit and the temp stays where it normally does then you probably dont have an air lock issue. with the car cool and the rad cap off you should see coolant start to circulate as the thermostat opens. ( probably not a necessary test)

Finally how do you know its actually running at those numbers?

Gun

 

well, im just saying thats what my aftermarket gauge reads, so i know thats not a tell all sign tho, as sometimes they are inaccurate. I would be fine with it running at 205-210, i just wanted to make sure damage wouldnt occur at those temps. How hot would it have to get before the motor might be damaged?

 

well its hard to call an exact temp but I would think sustained 270 would cause some serious problems after a bit. 250 would be maximum upper limits and should be avoided. I would think 220 would be okay if it starts to get past 230 that might be a problem.

I have had some rad lines leak and engine temp creep up and the rad cap has always popped before it did any damage.

These engines can usually survive burst temps of 300 (unless you have aluminum heads then all bets are off)

when its all said and done if you temp does not get above 220 at 50 mph and does not get above 225 at 80mph then you should be fine.

if you pop a rad cap in the parking lot or in traffic then its time for a new Aluminum rad Northern makes a great one at a great price.
Gun

 

the reason you are having issues is cause you have a 160 thermo thats like having no thermostat i would get a 180 atleast

 

i disagree BT!
the thermo will open wide at the given temp, plus or minus a few degrees. If its a cold day, it'll close down to restrict flow to maintain that temp.

if your rad isnt workign properly orits really hot weatherit will open wide and have no bearing on the temp at all.

badazz it might be worth trying a different gauge. you didnt say if you had teh rad cored or not.
if it is mild weather and all the system is working properly,temp should not rise in trafficcompared tocruising. If it is hot, then fair enough, but i'm talking into the 90's.

 

If you have a fan shroud and an efficient fan,you can control your temp better.I had similar issues,small 2 row rad,pathetic steel fan.I used to get too hot just driving down the street with a tailwind.I got the shroud and bought a plastic fan that really pulled a lot of air.went with a little more water than coolant and I have had no more issues with the same puny rad.