Ladies and Gentlemen,

I need some serious help with a 77 temp problem.

Little history for ya. I just recently bought this car and it has approx 1500 miles on total drivetrain rebuild. The engine is a stroked 383 with Brodix alum heads and full roller cam set up. It also has a Big Block 4 core alum radiator with 6 blade flex fan. Car has no AC and when I run around town the temp gauge reads 220-240. I have a direct read radiator cap which reads approx 140. The thermostat is a 160 which I just installed on Saturday. The car runs fine and it does not steam over as if it was hot nor does it smell hot. I am able to open radiator cap fairly quickly when I shot down also. I am jst scared off burning up a set of alum heads. I have new temp sending unit just haven't installed it yet. I will most likely drive it to work one day this week and shoot it the block with a INFARED GUN and see what it says. PLEASE FEEL FREE TO SEND ANY COMMENTS

 

First thing is to get a real temp reading. The temp sensor is in the drivers head, hottest part of the motor, I seriously doubt your running that hot. If you are and you have a 160 t-stat you have a flow/pump issue.
SO, get a real temp, then repost.

 

if you really are running those temps i would stop driving immediatly. prolonged temps like that will be killing your motor. if i was you i would invest a few bucks in a mechenical gauge and compare that to your electric unit. at 240 or above your engine should definatly be smelling like a burnt cat so maybe your gauge isnt accurate.

 

There are too many clues pointing to the temp sensor here. Replace that, it is easy and the likely source of your percieved trouble.

 

first, I agree with the others that you need to get a REAL temp reading before going any further. Use the IR temp gun and find out what your real operating temps are.
Not knowing what your real operating temp is makes us useless in helping you out. It's very likely it's nothing more than a bad temp sensor and you would not be the first one to chase his tail to try to find and fix an overheating issue that never existed.

second, replace that 160º t-stat with a 180º one. It will NOT lower your actual operating temps at all regardless of which one you use but assuming your cooling sysatem is up to par and can keep operating temps to where the t-stat level is 160º is too low of an operating temp. If your motor doesn't have all the factory emission rauipment on it than a 180º t-stat is the proper one to use.

Next, please get rid of the flex fan. They tend to self destruct and when they do they take large pieces of fiberglass with them.....

 

Needing more advice.
Temp sensor was replaced yesterday morning and before I was out of my neighborhood I was already at 200. Drove it to my insurance office for photos and it was up to to 250 on car gauge. I opened the hood and read the direct temp gauge on Radiator and it said between 180-200. While I was driving it home I noticed it drop a little sitting at a stop light and rise when I was accellerating. I just bought a new temp gauge and will install tomorrow. This really scares but it still doesn't boil over or smell hot though.

 

Where do you aim the IR gun?

 

Use the Ir gun on the sensor on the drivers head. Its between the #1 and #3 plugs, measure it there. It sounds like you have air in the system for the temp to fluxuate that fast.
You need to go thru the cooling system, each component at a time.
Make sure there is no air in the system, remove the T-stat, fill the system and see what it does. Look in the filler hole on the rad with the engine running and make sure you have good coolant flow.
Then drill a 1/8" hole in the t-stat and put it back in.
Make sure there radiator fins are clear for air flow, use high pressure hose to clean it.
Go to the chevy dealer and get some coolant system flush, its a powder that you add to the system and run it a while to remove the scale from the inside of the system
Make sure the fan clutch is good, when you turn the motor off the fan should stop within a half a turn, if it turns more than that its bad.
Make sure the fan fits correctly in the shroud, it should stick out of the shroud a little on the back side
Make sure the radiator seals are all in place
Make sure the Air Dam is in place and in shape

 

ALL these damn threads about overheating/running HOT....

take the damn thermostat out and TOSS it.....THEN post about conditions .....

first thing....every time....I don't care if the damn thing is NEW or used or borrowed or blue, it can be made of unobtanium.....

it's still the primary source of overtemp problems....

 

Noel48

My temp sensor is located just to to the right of my thermostat housing, when looking from the passenger side. I have aluminum heads so this is the major concern. I will be aiming the gun at the sensor and the t-stat housing.

 

Sixfooter,

Thanks for all the pointers, The sensor is located in my intake manifold since I have aluminum heads. The next thing is that I am runnning a six blade flex fan that is just mounted aft of the fan shroud. it doesn't matter if I run a 160 or 180 t-stat it still does the same problem. I am not sure about the air dam though, need to look at that. I think the main item that people overlook is the direct read radiator cap says 180-200 degrees. I have a complete new gauge unit to install tomorrow. First thing I will di in am is drive it around the block a few times and then shoot it with the IR gun. This will be my immediate indicator if it is the gauge I think. Do you think with the alternator belt being at the max could stall the water pump pulley, maybe the belt is lossening up and free spinning around the pulley? i do hear a little sqeal as i accelarate intially and then it subsides immediately. More to come tomorrow thanks for the pointers.

 

Mr Vette,

My goal is to fix my problem with my car not to temp fix it by removing the t-stat. I initially had a 180 and went to 160. Do you have t-stat in your 72? Based off readings from direct temp cap I think I am ok, but I am still not comfortable looking at a temp gauge reading 220-250 no matter if I know it is not that temp. If it is not a reading true tomorrow I will prob venture into a water pump since the radiator only has 1500 miles on it as the rest of the complete driveline. More to come tomorrow

 

Usually when the sensor is mounted on the intake the gauge in the car reads cooler than if it were mounted in the cylinder head. You seem to be experiencing the opposite according to the radiator cap gauge.

Shoot the sending unit, the thermostat housing and the top of the radiator where the cap is and see what you have.

I'd bet that either your sending unit or temp gauge are not accurate.

 

ok, it sounds like an airflow problem. If the temp in the rad is that hot then the motor is even hotter. Your fan sounds like its to far back so its not pulling air thru the rad but around the shroud.
Put a spacer behind the fan. Better yet, lose the flexfan, they make a mess of the hood when they let loose.
But its an air flow issue

 

I think we are on the right track. Do have the shroud installed and are the radiator seals in place around the radiator? Your modded engine produces more heat than a stock one. Just something to think about.

 

I agree with the comments about the airflow. The radiator shroud and foam MUST be in place to direct the flow of air across the radiator. If it isn't there, the air you need to cool will take the path of least resistance, which is not through the radiator.

Have you tested the temp gauge? I went through a similar problem when I started driving my car. My temp gauge was in the 220-240 range. On the suggestion of some forum members, I boiled a pot of water and dropped the sending unit in it for an instant gauge reading. After testing the sending unit it was determined that it was the sending unit/gauge that were reading 50 degrees high. After that, I installed a cheap mechanical water temp gauge with the sending unit in the passenger head and located the gauge in the clock position of the cluster. Now I can easily see my temp on the mech. gauge is 170 and the stock gauge is 220.

 

To ALL that have replied in an attempt to help me resolve my temp issues.

This morning i cranked it up in the garage and let it run for for approximately 16 minutes at idle. The only airflow in the garage is what was being produced by the car. Temps below were taken before and after start using INFARED HEAT GUN

Rad Temp Prior to start 82.5 / Block temp at T-STAT Housing 82.5

Rad temp after start 86/ Block temp at T-STAT Housing 92 @0910 AM
93 115 @0912 AM
105 140 @0914 AM
116 160 @0916 AM
126 170 @0918 AM
138 178 @0920 AM
145 183 @0922 AM
145 186 @0924 AM
140 188 @0926 AM

The temps above were all taken by an I/R, the car gauge read 100 @ start,200@ 4 minutes into the run, 220@ 6 mins and at the last gauge reading was 240 just prior to shutdown. I also shot the temp sending unit right at shutdown and it was reading 170. SO based off the data above I am pretty sure I have a bad gauge. Looks like local Chevy dealer will be seeing me for a new gauge order.

 

Sounds like you got a handle on it

 

Tell me about it, Sorry i cant post pictures of it for some reason.
Peter