LT1-LT4 Modifications 1993-97 Gen II Small Block V8

NEVER underestimate your own work!

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Old Mar 31, 2008 | 09:25 PM
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Default NEVER underestimate your own work!

As most of you know I bought me a 96 Z28 M6 recently and it had two problems...
The main problem is it is overheating. The former owner replaced the opti, plugs, wires and put on a new GM waterpump. And ever since its been overheating.
And when I got it I drove it while it was cold and gave it a good bit of throttle and it got to about 3500 rpms and it fell on its face.

I bought the car and started to fix it.

I looked at the plug wires and #3 and #7 plug wire was swapped on the optispark! "THANK GOD" I said, because it was such a simple fix!

Now for the overheating problem.
The heat climbs just like it should, not fast or slow and the fans kick on as they should. I tried to use the bleeder valves and Me and two Toyota Master Tech think the only air thats coming out is just the steem that is building up.
Also, once the car is warmed up, One side of the radiator is hot as where the other side it somewhat luke warm.
They think my radiator is clogged up!

What do you think?
Any help is appreciated, im ready to start driving my new car!
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Old Mar 31, 2008 | 09:27 PM
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Originally Posted by Green3spd
I tried to use the bleeder valves and Me and two Toyota Master Tech think the only air thats coming out is just the steem that is building up.
You should not have ANY air coming out. If you still do, then there is still air in the system and that could cause you to overheat. You should see only coolant (liquid) coming out after it has been bled properly.
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Old Mar 31, 2008 | 09:39 PM
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And you shouldn't be opening the bleeders when it's hot, either.

If you radiator is clogged (could be based on what your saying), that would explain the overheating.
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Old Mar 31, 2008 | 09:39 PM
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Well they say its just pressure building up because its not flowing.... we did it over, and over, and over, and over for awhile, same thing over and over.
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Old Mar 31, 2008 | 09:40 PM
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Originally Posted by SnakeOiler
And you shouldn't be opening the bleeders when it's hot, either.

If you radiator is clogged (could be based on what your saying), that would explain the overheating.
Why dont you open the bleeders when its hot?
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Old Mar 31, 2008 | 09:46 PM
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you probably have an air pocket in the line towards the back of the engine bay on the passenger side. the hose is above the bleeder and the radiator cap so the air builds up there. one trick is to jack up the front of the car and then while NOT HOT and engine NOT RUNNING and fill the radiator until it pee's from the bleeder then quickley close the bleeder and the cap. may take more than one round but one round did it for me.
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Old Mar 31, 2008 | 09:51 PM
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We put it on a lift today and just set the front of the rack and raised the front up. Then we turned it on and off, and steem would come out, then coolant, but it just kept coming. No way there was that much air.
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Old Mar 31, 2008 | 10:01 PM
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Originally Posted by Green3spd
Now for the overheating problem.
If you've determined that the system does *not* have air in it (which it
sounds like it does), do one other check.

On the front of the water pump, there is an inspection cover. When the engine
is cold, take this cover off - yes, water will dump out, because the water
pump's impeller is behind this cover. Attempt to turn the impeller by hand.
If it turns, I'll bet it's a bad drive coupler or stripped driven or drive gear.

I had a similar, intermittent overheating problem. It turns out that the water
pump drive coupler was stripped, which meant the pump was probably only
operating at 60-70% efficiency.
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Old Mar 31, 2008 | 10:04 PM
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reference here for proper fill technique: http://shbox.com/1/4th_gen_tech2.html#radflush
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Old Mar 31, 2008 | 10:23 PM
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if one side is cool and the other side is warm then yes it sounds like your radiator is plugged...backflush it and see what happens...
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Old Mar 31, 2008 | 10:25 PM
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Originally Posted by SnakeOiler
reference here for proper fill technique: http://shbox.com/1/4th_gen_tech2.html#radflush
Lol, I was on that sight already...
How long can this take to bleed the system?
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Old Mar 31, 2008 | 10:25 PM
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Originally Posted by 97badass
if one side is cool and the other side is warm then yes it sounds like your radiator is plugged...backflush it and see what happens...
Backflush? what do you mean?
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Old Mar 31, 2008 | 10:37 PM
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either take your hoses off or your radiator out and put a water hose in there and spray the water in there to where its going the opposite direction of the normal flow but stick a rag in around the water hose so the water can ONLY go into the radiator and not back out the way its going in
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Old Mar 31, 2008 | 10:42 PM
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Gotcha! They think I need a new radiator. I guess since im taking it out to change it I can test it that way...
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Old Mar 31, 2008 | 10:49 PM
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On my Blazer I had to take the water neck off and pull the t-stat out and reinstall it to relieve pressure to get it to flow ... it had air in it and it wouldnt budge
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Old Mar 31, 2008 | 10:52 PM
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Well.... pulling the thermostat out was one of the first things I did.
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Old Mar 31, 2008 | 11:34 PM
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Anything else?
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Old Apr 1, 2008 | 09:51 AM
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Like said above, i would check your water pump coupler. Like he said either pull the inspection cover off or take the whole pump off to see if its even there!
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Old Apr 1, 2008 | 10:16 AM
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buy a new radiator and i bet it will fix it.
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Old Apr 1, 2008 | 12:30 PM
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I just got it from the parts store!
Should be drivin it tonight............................ hopefully!

Ill keep you all updated!
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