I have 305 that is over heating. the gauges read cool but after 15 min of the car just sitting there in idle.... the water starts to overflow from the radiator cap... really hot. I thought it was the water pump but.. its not leaking and its not making noise as if the bearings went out. it has a brand new 160 thermo in it. the water that came out was full of rust. the car hasn't really seen any driving time since i bought it, but from just sitting there at idle.. the fan has never came on. Is it possible for the water pump to of gone out if its not leaking or making noise ? my next suspect is the radiator. is there any thing i can do to eliminate the suspects.

 

You probably have a bad fan switch, it is located on the passenger head in between cylinder #6 & #8, they are about $15 just try not to break the connector.

Whether your A/C works or not you can manually force your cooling fan to kick on by turning the A/C on temporarily until you replace your switch.

Parts can be dead out of the box sometimes. I would remove the thermostat rinse it off and test it. You can test it buy putting it in a clear pot on your stove with water and a thermometer, heat the water and watch the thermostat and see what temperature it opens at. If it doesn't open there is your problem.

Either way the wind shines you should flush your coolant if it comes out that color.

 

With the cap off the radiator,,start the car and look inside the radiator...look for gushing water from the heater core return line. is it gushing? next the water pump may seem ok, but if its not gushing the seals are bad..and 160* is bad bad bad. you should go stock, because the computer will have problems. if you do go the 160* mech thermostat route,,then you need a special chip (thermo master hypertech chip) AND the thermistor sensor that turns the fans on COOLER. i recommend the following..a new vented coolant cap .flush the radiator, next replace the the mech. thermostat with stock 195* or i what i run 185*. next go get DISTILLED bottled water(not purified or machine water, get two gallons. next, get two gallons of PEAK coolant, yellow stuff. mix the coolant 50/50 in a Tupperware and then put the mix into the radiator. BUt fill half way then unbolt the top radiator hose to radiator-and fill it up with the mixture to help eliminate airlock problems, you might spill it while reconnecting it. i wear latex gloves or nitrile for this purpose. antifreeze is like oil, very dangerours unless you get the pet safe coolant, which i tried out and got good results. always take spent coolant to a recycling place. after you fill the radiator, and top it off,- turn on car, let it warm up while topping it off. keep topping it off until the car get warm (the mech thermostat will open and the top hose feels hot.) replace the cap, and make sure the rez has backup fluid too. thats it. if youre having problems still, then report back. that should cure the problem..like the dude above mypost said,," a bad fan themosister or broken wire in the circuit could cause the fans not turn on. the fans should turn on about 210-220*. the car runs hot because the emission wouldnt pass if they were less. and when using the a lower mechthermostat the engine cant warm up and it affects other sensors. its not worth the headache trust me.. any spare left over coolant, re bottle it and store a gal in the trunk. its good, because it doesnt have minerals or chlorine and bacteria

 

Thanks for the advice. I'll try those ideas tomorrow. I got stuck helping family move today. One thing I forgot to note is that after my heater core started to leak... we took off the heater water lines. the water line that was running from the block to the heater core.. got routed to the radiator... that should be ok... right?

 

I took of the water pump and and looks ok... but then again its only $35. I took off the thermostat housing to make sure that i didnt have the thermostat on wrong and that was ok. So i took the hose to the manifold where the thermostat sits and let it flow... I had alot of rust colored water coming out of the holes where the water pump flows through... that took about 2 or 3 minutes to get the water to run clear. did the same to the radiator and it seems to flow good... so Im thinking its just a water pump issue.

 

thats cool with the heater hose id imagine. how old is you water pump.. mine is 3 1/2 years. my old water pump had bad seals and bearing because of too much belt tension, and prematurely failed. Um if your having the cooling issue ttill maybe you get a new fan themosister sensor w/connector http://summitracing.com/parts/HYP-4028/ you dont wanna go too cold, then the engine gets hesitation, because oother senors need to be warm 200 is ok..unless you get a mod chip for the ecm, then you can get a 160* mech stat and a colder thermistor for the fan.

 

I really don't know how old the water pump is. I just got the car a few months ago, but it looks like someone pulled it out of the ocean... rusty as hell. I will take your advice with the warmer themostat

 

my advice is a lower temp fan switch thermistor. the mech stat doesnt affect high temps, but it affect the lows. since youre having a high temp problem, then perhaps maybe its time to make upgrades. it could be the ethanol fuel added to the gas that makes the engine run hotter. back in 91' it was just plain gas. in the 21st century we got this hot burning gas ratio. The following is wat i would do..high volume pump, three core radiator or regular aluminum radiator, lower temp fan switch sensor, new vented cap, dual fans upgrade. try seeing if your fan shroud is intact. and last but not least the mech. tstat. I had a mech tstat constantly open(never closed) and my engine would take forever to warm, sometimes never would..i replaced it, and i got the higher temps i needed. but you have the opposite problem.
check this nice article out : http://www.superchevy.com/tech/0502s...ing/index.html

i wanna add, if your water pump is making any kind of noise, it could possibly be false alarming the knock sensor and thus retarding the timing of the engine. retarding the timing makes the engine hot. try re-timing the engine also. it will jump back and forth while revving thats normal, but at base timing (with ecm's advancing bypassed) it should be dead steady give or take *1. my base timing is *6 BTDC bypassed, with the ecm advancing. its well into the high twenties BTDC. I run premium gas. you have a lower compression engine so its safe to run the lowest octane 87.

 

The car is in needed of getting the timing right.. your saying that could have a part in the car running hot