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96 z28 overheating

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Old 09-11-2020 | 03:52 AM
  #1  
CASPEREPSAC-Z28's Avatar
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Unhappy 96 z28 overheating

hello I just bought a 96 z28 and it is overheating.i had the radiator replaced because I noticed the guy that had it before me put stop leak in it..idiot..I had the heads machined because the mechanic did a test on the coolant and said there was emissions in the coolant ..changed temperature sensor because I thought it might have been giving bad info but tested the motor with a manual thermo and it is definitely getting hot.the radiator was staying cool though.changed the thermostat to oem thermostat.the fans were already jumped to stay on when I got the car.i was thinking maybe the stop leak messed up the heater core or something is clogged inside from the stop leak somewhere.the car does not cool down when im driving in fact it seems to stay just before the red when im at idle with the car in neutral.when I give it throttle it seems to get hot quickly.i also noticed the oil pressure seems super low like almost none when im at idle but only when the car has warmed up.when its cold the pressure looks good.the same goes for the battery gauge it is low until I hit the throttle when its hot as well ..im not sure what to do next could any one give me some advice please..thanks.
Old 09-11-2020 | 11:33 AM
  #2  
Injuneer's Avatar
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From: Hell was full so they sent me to NJ
Re: 96 z28 overheating

GM actually calls for the addition of stop-leak pellets to the cooling system. Nobody actually uses them. A plugged heater core wouldn't cause the coolant to overheat. But it's easy to clear the core by pulling the hoses off the water pump, and runing water through the heater loop to clear the core. Mae sure no water splills on the Optipark distributor.

How many miles on the engine? Make sure the correct oil is used in the engine. GM recommends 5W-30 for cold climates and accepts 10W-30 for warmer climates. Excessive heat thins the oil out, and reduces pressure. The "check gauges" light will come on if the oil pressure drops below 6 PSI, which seems way too low. With engine fully warmed up, you need to make sure you have 10 PSI oil pressure for each 1,000 RPM.... e.g. 40 PSI at 4,000 RPM.

The "reverse flow" coolant system must have the air correctly bled from the system, or it will overheat. Shoebox's drain/refill procedure has a good air bleed procedure. Also several good articles on maintaining the coolant system - see items 12-20 in this list. When you open the radiator cap, the coolant should ALWAYS be right up to the top of the fill neck, with no air space.

4th Gen LT1 F-Body Tech Aids

Make sure the engine has the correct LT1 SPECIFIC thermostat. Stock is 180-degF. A 160-degF, with the fan on/off temps reprogrammed can help with cooling.

http://shbox.com/1/tstat.jpg

The stock cooling system should be able to hold theengine close to the 210-degF design point. If your fans were controlled by the PCM as in stock, the fans would come on at low speed at 226-degF and move to high speed at 235-degF. If someone jumpered the fans, the PCM no longer has any control at all.

Check the pressure cap. If the cap isn't holding the spec (18 PSI) you can boil the coolant.

Which coolant temp sensor did you change - the on in the water pump housing feed the PCM, the one in the driver side head is for the gauge?

If the overheating only happens at freeway speeds, check to make sure the plastic air dam under the front bumper is not missing.



Last edited by Injuneer; 09-11-2020 at 11:36 AM.
Old 09-11-2020 | 01:41 PM
  #3  
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Re: 96 z28 overheating

thanks for getting back to me so fast.i will do everything you recommended and get back to you.thanks
Old 09-11-2020 | 02:36 PM
  #4  
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From: Hell was full so they sent me to NJ
Re: 96 z28 overheating

Don’t forget the simple stuff.... like checking the front of the radiator for accumulated junk or a plastic bag.
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