I am thinking the water pump may be bad but wanted to give all symptoms and get some help. This is my daily driver so need to fix.

Car goes from 0-235 f in about 15 min, and will be in the red 10 min after that. Both fans come on at about 210. Water pump is two years old, and heater core is bypassed due to leak. Heater core has been out for a year now with no previous overheating problem. I took the guts(meaning the springs and everything) out of the thermostat to see if it would help and it did, but only delayed the process, still would get hot just took 15 min, instead of 10. No puddles or leaks under car and oil and water all look fine, as in I don't believe it is a blown head gasket.

Obviously need to replace heater core and thermo, but does it sound like the 2 year old pump let go? Also a friend of mine that races a 97 firebird LT1 said when his was on the street with his mild 383 like mine, it would do the same thing in that it just puts off too much heat for a stock radiator. And mine is exactly that, stock with 148k on it.

Water pump ? Radiator? Combo of the two? Please help? Also problem is recent, within the last month.

 

Since gutting the thermostat makes a mild change, it seems reasonable to say the water pump is moving the coolant around. My guess would be the radiator is partially plugged and not really doing it job. They are supposed to get rid of the heat. A stocker will probably work, but a larger radiator would be that much better.

As a side note, I've seen on a couple of times where the outside of the radiator picks up enough stuff that it becomes plugged up. Just rinsed them out from the engine side with a garden hose.

 

Ok I will give that a try, but the radiator looked prety clean as far as for debree and what not when we put the engine in last month.

That was the other thing I was going to mention and forgot. The water has a fair amount of rust and it is circulating but very slowly. Much less than what I remember seeing when the car was running fine. On the way home today it got up to 235 f in about 5 min and got in the red just as I was pulling in. I am not going to drive the car anymore as this condition is getting worse, but still very much appreciate ideas.

 

I would pull the radiator and go have it flushed! And make sure to take out the coolant level sensor otherwise they might ruin it. I had mine done and what a difference it makes!

 

Have it flushed by a radiator shop or get a new one. You would be suprised at how much stuff accumulates inside. If you remove the radiator, it will probably weigh a few more pounds than the replacement, because of all the stuff inside. You can really only see a very small portion when looking down on the tank.

The other sort of test is when the fans kick on, they should be throwing really hot air. I mean stick your hand in there for about two or three seconds kind of hot. If the air really warm, but not really hot, it's also an indication that the core is restricted. When it's flowing right, it can really transfer heat to the air.

 

Id get it flushed..How old is the thermostat? Is it a 160*? Make sure your WP is working, just to double check..

My 383 does just fine in the summer...doesn't get past 190*.

 

Possibly this may be the cause...
The gen 2 LT series reverse cooled motors have and internal bypass port in the WP. I have found that the poppet style bapass thermostat will not seal this bypass port to allow adequate cooling media flow from the radiator. The bypass port must be sealed off by the stat otherwise flow is reduced. This happens when the stat wax pill expands and exerts a force to open stat on the suction side (for cold media), and, seals the bypass port (@the block) when reaching design operating temperature (ie... a 160*F stat will seal the bypass port @ 180*F). Why failure???... I think the bypass portion of the thermostat wear out quick, and, do not seal (the metal disc deforms under heat, and wax pill expansion device is short on expansion). I'm moving to Evans cooling. Try evanscooling.com

 

I agree that a radiator flush / rebuild by a shop could help a great deal. However, before that point, I would verify that your lower airdam is intact and there is no air in the system. If you forgot to open the bleed valves when filling the system, it will have overheating issues. Try letting it idle and come up to temp with the bleed valves open and fill as needed to eliminate this before pulling the radiator for a flush.

 

X2 what everyone is telling you about cleaning the radiator coils ~ Camaros & Corvettes are bottom breathers and vacuum the highway as you drive down. I take the fans out, spray both sides with a mild cleaner like simple green and with a garden hose wash the coils from the engin bay out ward. Then take air hose & blow it out ~ you will be amazed at all the little stones, leaves, feathers, cigarette butts etc the car picks up over time.

If you are still hot, take the radiator out to a shop and have the inside flushed. Your water pump should not be a problem, its direct drive and even after you rebuild it, it should have the same effiency (same impeler/casing, the only thing you really change is the bearing/seal)

 

Just an update, replaced radiator and thermo and did not help any. However, watching the water with the cap off noticed that the water was surging,like only sometimes moving. We figure the impellar may have gone bad so I ordered an electric from summit and am going to replace it. With the fact that this pump is about two years old, I would recommend to all to STAY AWAY from ebay rebuilt pumps for $70 I think I paid for it with shipping, buy it now price.

Sorry for the delay but have been out of town. Just got married and went on our honey moon.

 

My car is doing the same thing...doesnt get hot near as fast but is running about 40 degrees warmer than usual. I cleaned the radiator out with the hose like others have mentioned, got some junk out for sure but didnt seem to help much. Think its just this ridiculous summer we are having around here. If I run the AC, it climbs really high.

 

have you bled your cooling system? you have two brass fittings, that you have to open up once your car reaches operating temperature. if you haven't done that it will fix it.

 

yeah I bled the lines, no air pockets. It has to be the impellar in the water pump because you can see the water circulating in the radiator with the cap off, then stop. Then it will start moving again and keep moving and then stop. It does this at all temperatures and when it stops circulating the gauge climbs higher,and fast.

96bowtie, you are right in that we are having a hot one around here in DFW, but all my years with these F-Bodies I have never had this kind of trouble. The water pump was shipped out today from summitt.

 

Temps going crazy like that in that short of a time period with the fans on and no blockage sounds like a head gasket problem to me. even more so when you said it was taking 15 min.. then it took 5 min ... just sounds like its getting worse .. i could be way off base here but this is what it sounds like to me

 

Its very rare for a radiator or thermostat to go bad. The very first thing you should do with an overheating problem on Fbody's is to do a pressure test. Pressure the system up to 17 psi and look for leaks. If the cooling system will not hold pressure then it WILL boil and overheat. Most of the time you will find a very small leak around a hose that is bleeding off pressure when it warms up.

The second most common problem is the mechanical waterpump. Check the weep hole on the bottom of the pump when you have pressure on it. If it is leaking replace it.

You can rent a pressure tester from Autozone for free.