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Overheating and im out of ideas

Z

zonacats

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Here's what I got, and 84 K5 with a brand new crate 350 from GM put in a week ago.

-New 350 (260hp / Gen 1 engine)
-New Edelbrock intake / 600 CFM carb / air cleaner
-Mostly all new engine parts (hoses, distributor, plugs, wires, etc)

A few days after getting the engine put in I noticed that the temp was staying normal for a few minutes and then rising pretty high (maybe 240 - 250 ish) for about a minute then going back down to normal (180-190 ish) and staying there for a few minutes then going back up again, then down, etc..

I figured maybe the thermostat (180) was sticking (even though it was also brand new with the engine). So I replaced it with another one and had the same problem. I then bled the system of any possible air pockets (twice) and same thing.

So I thought something is either clogged or to old in the cooling system so I went on a replacement spree and put in:

-brand new radiator (HD)
-all new hoses and clamps
-new fan clutch (HD)
-new temp sender unit in the head (and cleaned the connection up in the wire)
-all new coolant (obviously)
-made sure all the air was out of the system

So I get all that stuff put in and figured, ok, basically everything that runs coolant is brand new. Well, I start it up and the temp eventually rises even higher now (almost 260) and pretty much stays there so I had to shut it down. A few more test after it cooled and same problem.

So now Im at the point were its got to be the gauge. So I run to napa and grab a mechanical temp gauge with sender and installed it. I just put the new sender in and ran the cable out of the hood and through the window (redneck I know, but I just wanted to monitor it instead of actually instill it). At first it seemed better. The initial start up and warm up in the driveway stayed around 200ish. Then I went on a cruze around the block and it went up to 220-230. It came down a few times to about 190 but then went right back up.

Im at a loss right now on where to go from here. Any suggestions?
 
do you have a fan shroud?
 
yep, fan shroud is still in.

other things that may help for diagnosing:

-blazer is all stock (no body lift, suspension, etc)
-I made sure the overflow tank is full
-The only thing that has been removed from original engine configuration is the emissions equipment
-I am making sure I am following the engine break in, so It hasnt had much use (especially in higher RPM). All drives thus far have only been around the block for about 15-20 minutes at a time.
-the engine was installed professionally by a mechanic shop in my area.
 
My vote is for the water pump rotation is not correct.

Check it out as you might have been given the wrong one when you got the new one.
 
ok, that thought had crossed my mind, but I figured that since the mechanic put a brand new one in, that surely he got the right one. probably a stupid assumption though.

Any easy way to test that without taking it off?
 
No easy way.

Another thing to look for. Remove the pump (or maybe look in one of the hose inlets?) and see what your pump wheel looks like.

If it looks like this, replace it (right side):

chevy_camaro_2002_water_pump_oem_130_1780_1301780.jpg


Those stamped fins don't move the water and cause overheating.

If it looks like this, your pump is okay (right side):

chevy_camaro_1980_water_pump_oem_130_1070_1301070.jpg


Do you see the difference? The second one has fins that are formed to the cavity and actually pump the coolant. The first one just churns the coolant.
 
Still original Vbelt system. I will check and replace the water pump and see what happens.
 
-brand new radiator (HD)

Is the radiator cap new and the proper pressure???
 
I did buy a new radiator cap with the radiator. I got a 16lb one which is what the old one was and the parts guy said was the standard pressure.
 
One more thing I just remembered. The very first thing I did was replace the thermostat figuring the other one was defective from the factory. I was a little surprised that when i unbolted the water neck and lifted it off the manifold, coolant (a bunch of it) came flooding out like crazy (from the intake). I did NOT come from the hose, it even popped the stat out from the manifold like it was under some pressure. (think volcano)

The stat was installed correctly (spring down).

Do you think since it had so much coolant pressure built up in the engine that means its was trying to force it backwards through the system due to the wrong water pump? or is pressure like that normal?
 
Um,,, the spring goes up I thought.:dunno:
 
Nevermind me:doah: After looking at pics of the one I ordered I realize that it is spring down:rolleyes: I'm a dum bass:D Have you tried using an analog gauge once. maybe your electric is malfunctioning at the gauge end
 
Not according to the Haynes manual. It says:

"Make sure the correct end faces up - the spring is directed down into the housing manifold"

Edit: As to the gauge, yes, I went to the parts store and bought a brand new mechanical temp gauge ran it just out the side of the hood and through the window for a test drive. Same thing. Perhaps a little better but not much. It still hovered around 220-230 for quite a while.
 
someone mentioned the fan may be going the wrong way? That would be a good check too
 
Just checked the fan. How do I describe it with no pictures... umm..

Its spins counter clockwise (if looking at it from the drivers seat), and the blades are positioned in a way that they would NOT decapitate your finger if you put them in the engine side to stop the fan (although that would still hurt :haha:).

Wow, that's confusing, but I dont know how else to describe it. I am sure that by looking at it, that's its forcing air in away from the radiator and towards the engine.

I made sure and but the side marked "front" towards the front when I put the clutch on.
 
what about the coolant passeges, i remeber something when i replaced my intake manifold that theres was a passage that needed to be blocked on the RH side Passenger side.
 
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