overheating.

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85gbody

Greasemonkey
Jun 10, 2010
192
2
18
Long Beach, Cali.
Goodmorning gbody fam,
Last Saturday I was driving my el camino stock 305 on the freeway maybe 65mph and it overheated on me and the sound of a click clacking started. I pulled over popped the hood and the radiator hoses seemed to be filled with air, I let cool down and luckily I was able to drive home on the street route. Still to this day I can drive it locally without a problem but after a while it feels a bit rough and the hoses still fill up with air. Idk where to start, ii checked if the thermostat was bad but it wasn't either way I took it off. Possibly the water pump? Or would it be a blown head gasket?
 

khan0165

Royal Smart Person
Jul 14, 2008
1,617
15
38
Ontario, Canada
do you have a overdrive transmission? what kinda rpms are you seeing on the freeway?

the "click clacking" possibly sounds like a case of pre-detonation or "knocking", which could be caused by excessive combustion temperatures or excessive ignition advance. Check your timing (you can get a cheap timing gun for $20-30, or borrow one). Also, remove a couple of spark plugs and see what they look like... there should be an even colour distribution, minimal black suett, and hopefully not too much white.

when your engine is cool, open the rad cap and see if there is an oily residue mix in the coolant. While it's still cool, leave the cap open, start the engine, and wait for the thermostat to open. When the thermostat opens, you should see a steady flow of coolant into the rad. Rev the engine a little to see the flow increase or decrease...

Close it back up, then when your engine is up to temperature and running, observe the exhaust, is there white smoke? sweet smell? Inspect the oil dipstick, does the oil look frothy?
... these are indications of coolant going where it's not supposed

when your engine is running, does the lower rad hose (coming from the water pump) have good pressure in it? If pump is going bad, you won't feel alot of pressure in there.
 

85gbody

Greasemonkey
Jun 10, 2010
192
2
18
Long Beach, Cali.
wow lots of useful information i would of never thought about. thanks bro.

well, i dont have an overdrive transmission and have no tach in my car. (should invest in one, i know) but it doesnt feel like its running high.

ive had a problem with the timing not to long ago and wouldnt be surprised if it was again. ill check that out tomorrow if i dont work, or possibly after work today if i can get some lighting.

ive checked the radiator before, no oily residue, but havent done the reving with cap off. ill do the for sure today. i get no white smoke at all, no smell, and the oil looks good.

and yes ive checked the lower water hose and at first i feel good pressure after i drive it abit and check it again i cant telll cus both top and lower radiator feel plump with air. its pretty weird if you ask me.

ill follow these steps again just to be sure, thanks alot bro. i appreciate your well written response.
 

khan0165

Royal Smart Person
Jul 14, 2008
1,617
15
38
Ontario, Canada
just make sure what ever you do with the cap off, do it when the engine and rad are cold... you don't wan't pressurized hot fluid burning you. Once the thermostat opens up, you'll be able to see the coolant flowing into the rad... it should be a nice even flow, not super crazy fast, but nice and steady stream. Rev'ing up will show you if the flow increases or not.

Alot of times, steam and hot air can build up inside your cooling system if there is a leak somewhere, or headgasket problems. When this happens, your engine's heat is being transferred to the air and not fluid, so not much cooling happens. This could be the pocket of air you are feeling in the hoses, and could be the cause of your overheating.

Doing the cap off test will bleed out this air... As you run the engine and circulate the coolant with the cap off, the system is not closed and lets the air escape. Make sure you cap it back off once the engine is up to temp and coolant is circulating fully.

It should try to spill over without going into the overflow bottle (coolant expands and fills up the system under heat). If not, you might need to add some.

if after doing all this, you are still finding air buildup in the cooling system... then we have a problem, and need to see where this air/steam is coming from (leak? headgasket? etc...)
 

jmt455

Master Mechanic
Jun 26, 2011
402
3
18
SE Michigan
Another thing to look for; once the thermostat opens and you can see the coolant movement in the radiator, look for bubbles in the coolant. That can be a sign of a bad head gasket or combustion chamber/cylinder leak.
 

Bonnewagon

Rocket Powered Basset Hound
Supporting Member
Sep 18, 2009
10,540
14,217
113
Queens, NY
I don't know why, but I've been seeing a LOT of bad thermostats, even brand new ones. That's why I test every one by heating it up in a pot of water with a candy thermometer. As the temps rise, you can see when it opens, and more importantly, when it closes. A LOT don't pass this test.
 

jmt455

Master Mechanic
Jun 26, 2011
402
3
18
SE Michigan
Bonnewagon said:
I don't know why, but I've been seeing a LOT of bad thermostats, even brand new ones. That's why I test every one by heating it up in a pot of water with a candy thermometer. As the temps rise, you can see when it opens, and more importantly, when it closes. A LOT don't pass this test.

^X2!!
That's good advice...I dealt with this on my Bonneville.
 

85gbody

Greasemonkey
Jun 10, 2010
192
2
18
Long Beach, Cali.
so i ran it while the engine was cool, water flow seemed to be good, reving it obviously made it pressurized more like khan0165 stated.
also about the thermostat, i removed it, idk why but many car people told me to do it before, and i have and my other car ran good without it. but why is it that they say this? so i removed it because thats what i thought was the problem.
i let it circulated because i thought it was just air build up as well. tomorrow hopefully ifits not as dark i will check the spark plugs and timing, thanks fellas.
 

jmt455

Master Mechanic
Jun 26, 2011
402
3
18
SE Michigan
Without a thermostat it will run too cool (except maybe in Death Valley).

That means inefficient operation, potentially higher emissions and, worst of all, probable sludge build-up because the oil is too cold...and of course, poor, if any, heater output.

When the thermostat in my 305 was stuck open, the engine ran like crap (still have the original CCC carb and ECU).
 

Bonnewagon

Rocket Powered Basset Hound
Supporting Member
Sep 18, 2009
10,540
14,217
113
Queens, NY
Without a stat in cold weather it will run cold, but in hot weather it can run hot because the coolant flows too fast and the heat doesn't have a chance to transfer from the radiator to the airflow. That is why even a race car uses a restrictor (like a big washer) to slow down the flow. Are you using all the required stuff like overflow tank, clutch fan, radiator shroud, pressurized cap? Is the radiator in good shape? Water pump? I hate overheating and except for a bad stat, it's usually a combination of things.
 
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