quadabaum

Alright so i swapped a 350 into my 1991 firebird that originally had a 305. It keeps overheating in traffic and at idle or anytime im not moving. I changed the thermostat to a 160 and that made it run a little cooler while moving(about 220 when moving) but still constantly overheats when im still or going slow. My waterpump works fine and my air dam is still there. My fan is on a switch and i run it constant but doesnt do much at all. Please help!!!!

i have already tried a warmer thermostat but that makes it run hotter quicker.
My air dam is still under the car.
waterpump works.
Please help!!!

houston_boss

Well when it comes to overheating issues, it's usually one of a three components that's failing. The fan, the water pump, or the thermostat. This is very generally speaking, as there are obviously other causes, but I would make sure these are all ok first.

What do you mean the fan isn't doing anything? That sounds like an issue. haha.

quadabaum

i meant the fan isn't cooling the engine any really. It works fine, has a brand new motor and i got it run to a switch but it isnt helping keep the engine from overheating in traffic or at idle.

Gisys

Let the car sit over night. The next moring start the car with the rad cap off. Is it bubbling up at the cap? Small bubbles? Bubbles should start with in 5 min's. You may have a head gasket problem.


Oh yah one other thing is do a compression test on the rad see if it holds you may have somthing elsewhere as well..

camaronewbie

What's the timing set at?

Have you cleaned the gunk/leaves/stuff from between the radiator and the A/C condensor?

Is it REALLY overheating, or is the guage just reading hot? Really overheating means it boils out into the overflow tank, and makes steam - just because the guage reads hot doesn't mean it is hot.

quadabaum

engine was rebuilt before i put it in and ill check for bubbles.

temp gauge reads hot but i havent seen steam or anything coming from overflow tank. should i get an aftermarket temp gauge?

new radiator in it and i cleaned the junk out when i replaced it. the a/c is removed so that condensor isnt even in there anymore.

camaronewbie

If it's not physically overheating (ie spewing hot coolant all over the road), then it's not overheating. These factory guages can be way off even on a good day.

I'd try replacing the temp sender, driver side head between #1 and #3 cylinder - has a single dark green wire. It may be the case that the motor you swapped in has the temp sender for a different/older setup - get the temp sender for your year/type of car.

You want this: http://shop.advanceautoparts.com/web...S_575658306___

To set your mind at ease - go to a local shop that has an infrared temp tester, let the car idle in their parking lot until it gets to where you think it's too hot, and let them test the temp on rad hose, thermo housing, etc and let you know what the REAL temp is.

Or, you can leave the cap off, run the car until it gets hot, and use a CANDY thermometer to test in the radiator to see real temp.

I'd try a new sender before I bought aftermarket guages.

1983Chimaera

Look up my thread "Heavy duty cooling mods" for some ideas if you need more cooling than stock. As for your current issue, check a few things. First, with the car cool and off, burp the cooling system thoroughly until it is completely full in the radiator and up to the cold line in the overflow tank. Then start the car with the cap off the radiator and keep burping it with your hand over the radiator cap opening to seal it, checking every 30 seconds or so to see if the level is going down. This will make sure you aren't air bound in the system somewhere in the motor. Once you feel the coolant start to warm, go ahead and close the radiator up. Once the thermostat opens you should feel the upper hose get warm quick and pressurize, which will verify you have proper thermostat operation and a properly pressurizing system, knocking out three checks at once. If all that works, let the engine run about 10 min (checking your temp gauge), and make sure the fan is working as it should. Also check for leaks on the engine, like the water pump weep hole, where the pump meets the block, around the thermostat, around the hose connections, etc. Check the oil and make sure it doesn't look like chocolate milk, indicating a head gasket allowing coolant to blow into the oil. Check the exhaust, putting your hand in the exhaust stream for a moment then smell your palm; if you smell a sickly sweet smell, you may have a head gasket allowing coolant to blow into a cylinder. If all this passes, and the water pump isn't weeping or making cavitation noises or squealing, then you may just not have enough cooling for the engine. Your next step (assuming your current components are in good working order, I.E. clean radiator filled with distilled water / coolant 50/50 mix, working water pump, working fan, working thermostat, etc), is to look into either a heavier duty radiator (multiple core, I run a triple core brass tank radiator in my '83 Z/28 from Auto Zone), auxiliary fans (as detailed in my other thread), an oil cooler, or a flex fan.

quadabaum

thanks for all the help guys and pls continue to give ideas. Just to clarify i havent let it overheat, just when sitting still or in slow traffic the heat constantly rises without stopping. It just keeps rising and i usually get back moving before i let it reach critical temperature. i will go get a new temp sensor today and see if that gives me more accurate readings. I could get the temp sensor or a aftermarket temp gauge.. which would be best?

1983Chimaera

I like the idea of using a laser thermometer to see what your actual temp is. If it keeps rising tho, then you definitely have some sort of issue. Do the checks I detailed, that should help narrow it down, or at least eliminate the most likely causes. It may just be that your 350 is a little too much for the stock cooling system to handle in your climate. I have a 327 and live in San Antonio, and between the humidity, heat, and traffic, come June my car starts to get a little warm. After I did the mods to my cooling system it stays right at 180, no matter if I'm running WOT or idling in stop and go traffic, day or night, hot or cold out.

quadabaum

i live in ga so the climate here can be humid and quite hot. like where you live at. ive checked for leakes and dont have any and ill do the other lil things this afternoon that you listed. ill also look into the mods you did on your car. i read the article and ill see if i can maybe get moving on doing some of that.

camaro1185

Is it possible for the fan to have been mounted backwards?

1983Chimaera

If it's the stock electric fan then not really, it's pretty much only capable of being mounted one way. Third gens aren't known for having the greatest cooling systems around, I've talked to plenty of people that have completely stock cars with 100% functional cooling systems that refuse to stay cool on a hot day or in traffic. Before I put my 331 in I had a stock 305, and even it had issues staying cool with the stock fan. That was also a year we had torrential rains all summer, with 95+ degree heat and ridiculous humidity.

camaronewbie

Never heard back from you what timing is set at - timing too far off can make car overheat as well.

I'm running stock 305 TBI fan, motor, radiator, and I have no issues in NC summers at all with my carbed 350 with headers, and last summer was a scorcher here. And I had no issues in ATL at the Gathering either. Of course, I'm not running stock fan wiring, I'm running an aftermarket adjustable controller so I can set it to a lower starting temp in hot summer months, so it comes on sooner and reduces heat earlier.

Humidity only affects animals, not machinery when it comes to heat. Ambient temps are all any metal knows anything about. And since engines are (usually) under hoods, even direct sunlight (radient heat) has no effect on engine temps, other than the fact that the out-of-hood temps are higher in the sunlight, and thus the underhood heat doesn't dissipate as quickly as it would with lower out-of-hood temps (heat rises, but heat rises faster in cooler air than it does in warmer air).

1983Chimaera

Per the US Navy Nuclear Power School: Material Fundamentals Course - Humidity affects HOW the metal reacts to change in ambient temperature. High humidity or wet conditions films the metal and creates a cooling effect while heating up until full temperature is reached. This can cause uneven expansion of connected same metals resulting in failure or stress.

Quoted from a Machinist Mate (Nuclear) 2nd Class with a B.S. Mechanical Engineering primary discipline - heat transfer and fluid flow fundamentals - Penn State.

camaronewbie

Humidity might do all sorts of things to anything - What I meant was the car does not 'feel' hotter or get hotter or run hotter due to an increase in humidity - your AZ desert car with 100 degree day and 10% humidity should not run any hotter than my FL car with 100 degree day and 87% humidity. Sorry, thought that was an apparent concept.

1983Chimaera

Actually, it will. The increased humidity will condense on the fins and coils of the radiator when the car is not moving in high humidity, affecting the cooling ability of the radiator and causing the car to run hotter. When the car is moving or with adequate airflow from a fan, the condensate on the fins and coils will actually help the radiator to cool, causing the car to run cooler. This is all basic air conditioning theory: heat transfer. Conversely, dry air moving constantly over a radiator will only have increased cooling ability based on airspeed and the air's base temperature. It's called latent heat reduction.
The problem is the stock fans in these cars are woefully inadequate for warmer climates. As reported by numerous people in my region and in other warm wet areas, these cars have a tendency to heat up even in stock configuration when sitting in traffic. 220 is not acceptable for a car with a stock 195 degree thermostat.

kymission

iTrader: (1)

I suspect that the timing is retarded. Make sure that the electric advance bypass is unhooked and check the timing. I had similar issues for a day or so when I did my 350 swap.

gsmarcano

, Exactly. evaporative cooling.

naf

iTrader: (7)

Apparently has an edelbrock carburetor on it. I sure hope that it doesn't also have the stock distributor still spinning. That alone would cause an over temp problem at idle.

Ron U.S.M.C.

Did someone say replace the cap ? Could not hurt for the $6.00 it would cost.

quadabaum

I replaced the cap the other day and didnt seem to do anything. Thank you though

Also my timing was set by the guy who put my engine in and i believe its not 0* but i cant remember exactly what its at. Also my advance timing is set and he checked that and said it was fine. So im gonna rule out timing for now but thank you for the advice.

quadabaum

It has an MSD distributor on it.

Gisys

Did you do a pressure test on radiator?

naf

iTrader: (7)

The OP says it has not boiled over so a new cap and pressure testing aren't getting him any closer to solving his temp guage problem. Until it boils over the motor is NOT overheating. Double check it: let it idle in the driveway for a while. Let the temp guage go where ever it wants. See if it boils over. See what the temp actually is. Connect a cheap mechanical guage into the water neck.

quadabaum

So today i saw that my lower radiator hose has been compressing. SO im going to get a new one and see if that helps keep the car somewhat cooler. What year is it that had the spring in the hose? All the auto stores wanna give me one without a spring in it and i'd rather have the one with the spring. So does anyone know the specific model and year firebird that has the spring in the lower radiator hose? Thanks again everyone and ill inform you on whether this works.