95z26

aintlifegrand · Post by **aintlifegrand** » Fri Oct 13, 2006 1:52 pm

car overheats (3/4 to red) after about 15 minutes of interstate driving. Will idle indefinately between 1/2 and 3/4. Had thermostat changed, still getting hot. Fan runs but wont cool to below 3/4. Plastic radiator cap (are those the ones that go faulty?) Also, may have small leak in metal line that returns to overflow resevoir. Could this be letting air in the system? Any suggestions or ideas would be GREATLY appreciated! (This POS has been sitting in my garage for 3 yrs due to this problem, among others)

wicked-irocz · Post by **wicked-irocz** » Fri Oct 13, 2006 6:10 pm

could be a clogged catalytic converter.

docrodg · Post by **docrodg** » Thu Oct 19, 2006 9:31 am

Try flushing the system. The radiator is only a one core so any clogging really messes it up. You could just take it out and get it boiled.

aintlifegrand · Post by **aintlifegrand** » Wed Oct 25, 2006 12:58 pm

How difficult is it to take the radiator out and where would i get it boiled? I changed the thermostat (again) and it worked great for about two weeks. Then last night, it overheated again (in winter, in montana). Also, one question that will seem stupid to most, which way does the coolant flow. Standing in front of the car with radiator, water pump, block, thermostat, radiator being a unit, does coolant flow clockwise or CCW? The rubber hose coming out (going in?) to the thermo gets rock hard when the car does its overheating thing. Enough pressure that coolant comes out the plastic radiator cap. Also what are the symptoms of a faulty radiator cap? Sorry about the long post and thanks in advance for any advice.

aintlifegrand · Post by **aintlifegrand** » Wed Oct 25, 2006 3:19 pm

One more thing that just occured to me.. when I changed the thermostat, it took days for low coolant light to go off. Another sign of a plugged radiator?

spacecadetz26 · Post by **spacecadetz26** » Wed Oct 25, 2006 5:54 pm

what brand thermostat are you using? I've had Stant's go bad after a week. I changed it 3 times before i got fed up and put in a AC Delco. You also need to bleed the cooling system. there is a bleeder screw on the black heater core pipe that goes to the timing cover near the water pump. after you fill the overflow all the way and the low light doesnt go out try tapping the tank with a hammer and it should dislodge the air pocket at the sensor

docrodg · Post by **docrodg** » Wed Oct 25, 2006 6:01 pm

OK... here goes.

Coolant flow is from the top of the radiator to the bottom. Water comes out the bottom into the water pump then thru the engine and out the thermostat into the top of the radiator.

The overheating: THe boilover (overpressure causing fluid to fly outta the cap) is caused by only a few culprits typically.

1. The radiator cap could be bad, lowering the pressure that the system has which then lowers the boiling point of the coolant.

2. The fan is not coming on, but this is ruled out in your case by the fact that the car overheats on the highway too when air flow thru the radiator is enough to prevent the need for the fan.

3. The radiator is clogged. THis reduces flow thru the radiator and prevents cooling of enough volume of the fluid to cause the overheat. This is why the larger the engine the larger the radiator, more fluid to cool. The radiator is not just size but number of cores (1,2,3 etc.) a typical old chevy v-8 ran with 3-4 cores in most cars, the beretta has a small 1 core radiator. THis means if it starts to get clogged up there is no other path for cooling.

4. Faulty water pump. This would normally be accompanied by screeching and bad belts. If the coolant isn't pumped it just sits in the engine getting hotter and hotter. The pump could be bad in that the impeller is rusted out or disconnected inside but this is very unusual and most of the time still makes noise.

5. Bad thermostat. Not opening when warm preventing return of coolant to radiator.

How to figure it out?

Thermostat is easy, start car and let warm up, feel upper hose to radiator, should have pressure and be warm to hot.

Get the cap tested or just replace it.

Disconnect the radiator hoses, Look inside both hose connections with a flashlight and see if you can see the core, should be lots of holes running the length of the radiator (the core) and they should be clear. Run water thru from the top (use 2 hoses if possible for supply), see if it comes out clean and in large volume.

reconnect the radiator and take off the thermostat housing. FIll the system and with the hose still trickling in the radiator fill port start the engine and run for a moment to see if water comes shooting out of the housing. If so pump is ok. Drain water, reassemble, and put in mix.

The fan should come on by 3/4 of temp gage. look, if it does ok, if not fault in motor, wiring, relay, or thermocouple. Check for voltage at fan, then relay output, then relay input, then thermocouple. Where voltage is lost indicates what is bad.

Warning, if the radiator is clogged bad enough they can't boil it out and you will need a replacement. New radiator: 120 bucks (just did one a few months ago due to a hole in it).

aintlifegrand · Post by **aintlifegrand** » Wed Oct 25, 2006 6:19 pm

I am definately suspecting another bad thermostat. (Yeah it is a stant, all that NAPA would sell me) Radiator could possibly be plugged also as i may have put sawdust-looking sealant in there to try to fix the headgasket leak. (I now know this was a bad idea, but i cant remember if i actually did do this or not.) I am definately going to replace the thermo again (it did great for a week after i did that last time) and the rad cap, then radiator if nothing else. I will also make a note in the common diagnostic? section here to never ever buy a stant thermo. Thanks for all the replies, they are greatly appreciated!

aintlifegrand · Post by **aintlifegrand** » Thu Nov 16, 2006 8:56 pm

Just an update in case it helps anyone else.... problem seemed to be POS stant thermostat. I got an acdelco and have had no problems so far.

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