so ive read some threads on here but im not the biggest car guy to understand it all. so i had a few questions but some info first.

350 small block rebuilt (not sure how long ago) 69 impala
automatic transmission
redone radiator ( 2 weeks ago got this radiator cleaned and rewelded)
fan w/ shroud
brand new sunpro temp gauge and new 18o degree thermostat

installed the redone radiator and thermostat put in the cleanse and ran for about 30 miles and then flushed the motor and radiator and refilled with 50/50 coolant. few days later it was overheating so i turned it off and drove my truck for awhile. next day i reflushed it because there was a sort of sludge at the top. opened where the thermostat was and thermostat was completely clogged with a chocolate moose looking sludge. took the thermostat . took the top hose off and hooked up the garden hose. ran the engine til water came out clean. replaced with another new thermostat and refilled with more 50/50 coolant. runs to about 210-230

to the questions
how hot should it run at?
what temp would my thermostat go out on me? is it possible that it overheated the thermostat and now the thermostat is stuck at 180?
started smoking right when i turned the car off and was still reading 180

ANY info would help. bought this car to learn on but this one has me stumped
thanks in advance

You must really have a lot of sludge in there, are you sure its all cleaned out now, also are you sure the water pump is working and have you checked your oil to see if there was coolant in it?

Is it running this temp going down the road or at idle?.....Cole

thought the sludge was out ran the hose through it for a good 15 minutes with the engine running and the top hose off to shoot out the sludge and rust


have not checked the oil for coolant.. i know oil looks milky with water in it. same with coolant?

it seemed like it was staying steady at 210 when it was idle but was not cooling down at all. there was a bit of white smoke when i opened the hood after it was reading 180 thought it was just oil leaking out the header

Read through this wiki article and see if anything catches your attention....
http://www.crankshaftcoalition.com/..._cooling_system

I have been dealing with overheating issues on my 350 also, and here some general info that I have found out, after spending weeks reading and tinkering.

A thermostat stays closed until it reaches its rated opening temp. in your case it is 180 degrees. So when the coolant in your block reaches 180 degrees, the thermostat opens, and the coolant starts flowing into the radiator, and the cool coolant starts moving into the block. When this happens, you should see that your temp gauge, should slowly rise to around 180 degrees, and start to slowly go down, then slowly go back to 180, and back down, as the thermostat opens and closes, etc...

If the temperature of your engine is reading above 180 constantly, that means that the coolant isn't getting cooled, in the radiator for whatever reason. So start looking at your fan, fan shroud, radiator flow etc. Also, i would recommend just replacing your water pump regardless if its shot or not. they cost 30-40 bucks max, and solves a lot of issues.

What type of fan do you have? a clutch fan can go out, and cause issues like this. Consider getting a flex fan, or a replacement clutch, or a clutch bypass for the fan you have, if that ends up being the issue.

You may want to consider getting a higher temp thermostat, if all the hardware checks out. For example, if you install a 190 degree thermostat, the coolant will spend more time in the radiator, being cooled, between the hot and cool cycles, that is supposed to happen in a correctly operational cooling system.

yea i need to check the water pump.

thanks for the tips. i have a flex fan..
what temp is too high for the thermostat to give out?

Well, we're making progress. You've identified one of the problems.

Whats wrong with a flex fan? I've been doing a lot of reading and it seems to be a better solution than replacing the clutch fan I have going on in my truck.

I would really like another opinion on the situation...

Reminds me of a Rodney Dangerfield gag. A guy goes to the doctor. The doctor says "You're fat". The guys says "I want a second opinion". The doctor says "OK, you're ugly too".

Unless they have made great strides in the design of flex fans, the ones I'm used to seeing are too small in diameter and too thin in pitch. You need an 18", 7-blade fan with a nominal 2 1/2" pitch to move enough air through the radiator.

will the difference in fans make a 30 degree difference? or should the fan be the last step

still would like to know if theres a temperature that will ruin my thermostat... like 220+?

thanks

Flex fans are junk and are only a time bomb, plus they rob power, a clutch fan is the best second only to a electric fan. a good heavy duty clutch fan spaced properly in a fan shroud , works great. and has a min loss in power going down the road. also make sure you are not using to low of a tstat. Not only does it keep water in the block, water also has to stay in the rad long enough to be cooled . The sludge you spoke of kinda worries me though, could Be a bad headgasket.

hmm is it possible that the engine flush i used is still cleaning gunk out of the motor? ive driven it about 60 miles since i used it and i said to drive 70 -100.

opened up the radiator and it has the same brown gunk in it. does not look like theres any oil mixed in with anything. its literally like fluffy dark brown dirt.

not the head gasket..still a mystery