KevinK

So, per suggestions, and after replacing the fan clutch, I DID manage to keep it SOMEWHAT cool for the break in, with water on the rad and everything. By somewhat cool, I mean...it didn't go past 235.

Now, at idle, it takes a LITTLE less time to get up past 200, but it still just sits there and overheats. The timing is down, it idles and sounds AWESOME, it's just not keeping cool. I've got a lunati voodoo cam, new GMP vortec intake, vortec heads, shorty headers, new radiator, new fan clutch.

Here's the thing. How do I tell if I have a faulty water pump or not? I DID replace it, but I replaced it with one I bought from a forum member, Durango Boy. Now, I want to believe he did not sell me a bad part...but...it's the only think I can think of at this point. There is nothing else in the entire cooling system that has not been replaced.

Also, some vortec swappers specific thoughts. Could it be a communication error between the 76 gauges and the newer temp sender unit I had to get, due to size differences?

And last, I have an issue with my upper rad hose...the T stat house is larger than the old one was, thus, the hose does not REALLY fit over it...right now, it's stretched (read bubba'd on there). BUT, if I get a hose that fits the housing, it'll be too big to fit on the radiator end. Thoughts? And thanks.

'75

I did the vortec head swap. I used the original thermostat housing, it worked fine. Did DB sell you a reverse rotation water pump? Water pumps are so cheap, there's no reason to buy a used one, $30. Did you switch to a serpentine belt also?

You likely have a miss match with the sender also. For mine, I drilled and tapped the hole in the head to 1/2 npt and used the original sender. If you have an extra hole in the intake manifold or thermostat housing you can install the original sender there.

KevinK

No serp belt, that I left alone. DB sold me the water pump knowing I planned to do a vortec swap...so I can't imagine he would have sent me something that was a reverse rotation. Is there a way to tell, after the install? I bought the new housing for the T state because on the intake, the old one was too small, threads did not even come close to matching. And the temp sending unit, same story. Stock temp sender was smaller than the threads in heads. Is there a way to tell if a water pump is not doing it's job, other than having a motor that runs hot?

'75

With the engine running and the radiator cap off, look in to see if coolant is flowing out of the tubes and dropping into the right side tank. Are you using a new thermostat? You could remove it for testing purposes and see if it heats up slower.

Your original style water pump should work fine, there is no change required for vortec heads. All the original vortec engines used reverse rotation pumps because they all had serpentine belt systems.

BKbroiler

As '75 mentioned, try installing your original temp sender in the intake manifold, not the head. On my Edelbrock manifold there is a tapped hole, correct size near the thermostat location. It came with a plug in it from Edelbrock.

chevymans 77

When working out my heating issues I ran across the hose mismatch issue. I used an 1 1/2" hose due to the T-Stat housing being that size but the inlet to the radiator was 1 1/4", I used a small section of 1 1/4" hose on the radiator inlet and than slid the 1 1/2" hose over it, it was a good snug fit.

I've also used a section of clear tubing like you find at home depot on the upper radiator hose just to check flow. I wouldn't let the car get hot due to I didn't know what temp the tubing was rated for. You'll be able to see the flow from the motor to the radiator. I can tell you that the water pump will put up plenty of flow if its right, surprised me how much flow there is. I did this test without the T-Stat installed.

You can check the temp sender, put the stock one in a pot of water on the stove and bring it up to 180* with an ohm meter check the ohms, now take the new one that you are using and do the same see if they are close. There is a chart on Willcox's web site that lists what the stock one should be a given temp.

Neal

Artsvette73

From what I have seen the reverse rotation pumps have a diffrent bolt pattern for the clutch fan. So your fan clutch would not bolt up. First thing I told the machinist when I had the heads done was to change the size of the temp sender hole. Why is your timing low? That for sure would cause high temps. An IR temp gun will give you some good readings and will tell you if you have a temp sensor mismatch with the gauge which I believe you have along WITH THE TIMING

Lee H

I assume you verified the overheating condition with an IR gun. These old senders and gauges can not be trusted with out verification. The gauge in my 65 reads 220 but real temp with IR is 180. Good luck.

mvette76

it is the sending unit! i had one in my vette it always read high. just did a head swap and drilled and tapped the head for the right sending unit and it reads right around 180 now

mikep3

I did a Vortec Head Swap two years ago.
180 "T" stat. and the temp would go up to 210-215 when the engine first heated up and drop to 180 to 190. I ended up drilling a small hole in the "T" Stat and that problem went away.
I am using a 79 temp sender 3/8 NPT instead of the 1/2 NPT 78 sender. So I got a $20 IR=Temp gun from Sears and verified the temp. The car's gage reads low on the low side close at 180 and high over 200, the highest I tested was 210 by turning off my electric fan.
-Lower inlet hose needs spring or check for collapsing.
-Water pump is good and correct rotation for drive belt system.
-Radiator is not plugged or restricted air flow.
-Air dam and radiator foam is in place to prevent air going around the rad.
-Verify the Temperature.
-Timing

KevinK

Going to see if I can find a spot for the old temp sender somewhere on the intake, thanks for the advice! And the timing is not retarded or anything, I meant that the time it takes to over heat has gone down. I had my buddy help me with the timing, and it's perfect. Barely touch the key, and the sucker jumps to life like it was fuel injected, and goes right to a beautiful idle.

As for checking the water pump...I thought it was dangerous to take the rad cap off while the motor was running? Isn't that gonna spray me with coolant? Not doubting...but I also don't want to go to the hospital with flesh burned off my face!

KevinK

Never mind. It's like.....100 degrees outside. Maybe I'll check these things in the evening.

ZBRA

Verify the gauge is reading correctly first.

If it is, swap your old water pump back on and see what happens. You may have gotten one that's reverse rotation.

When purchasing a water pump, you need to make your selection based off which engine and belt system you have, not which heads you have.