i think there is air in my cooling system. the temp will go up to about 220,then shoot up faster to about 240 or so. then u can shut it off for lke 30-45 seconds and start it back up and the temp is down to about 140-150 or so...and the cycle goes on again.
it has a 180 t. stat in it w/ a small hole drilled in it (about 1/8" or so) and the water pump is about a year old or so.

its wierd,u can touch the valve covers on each side and def. tell that the driver side is hotter than the pass. side.

is there a good way to somehow get the air thats trapped in there out?

me and my dad were messin w/ to for a while and thought we had it,but took it out and drove it and it went up again..but was alright at idle before we took it off...it just pisses me off that its being a ***** like this.

 

Take off your rad cap and look for bubbles. It sounds like you have a blown head gasket.

 

I'm also thinking head gasket. Pull the plugs... if one is Very Clean then you likely found the leaking cylinder. They should be lightly tan and a little black powdery appearance. Tan is better. Clean is bad.

 

it has bubbles when it gets hot in the rad. b/c we ran it the whole time in the garage w/o a cap on it to make sure we had circulation...head gasket isnt blown,no white smoke outta the exhaust and not running on less than 8 cylinders.

 

It should not have bubbles in the rad if you have run it for a while because the bubbles should have purged by now. You need to run a pressure test on the cooling system. Also look at the plugs and see if there is white on any of them. Also, a leakdown test might be in order.

 

The purpose of the cap isn't only to simply keep in the coolant. It's other purpose is to pressurize the system. By pressurizing the system, the boiling point is raised to 250*F depending on the mixture. By leaving the cap off, you have disengaged any potential the cap had (if functioning properly) to pressurize the system. You will get bubbles because the system is boiling. Also, each bubble that boils will create a 'hot spot' as the air displaces coolant away from the cylinder in the water jacket. Those hot spots can warp and distort metal very quickly. You may have a blown head gasket.

You'll have to pull the plugs and check... better yet, run a compression test.

 

Bubbles in the coolent is usually an indication of compression (blown head gasket). You won't always have white exhaust since it depends how the leak is formed.

Other than the above mentioned things to test you need a rad tester. Hook it up to the rad and start the engine. Under normal conditions, pressure will only build up after the coolent starts to get hot. If a head gasket is blown, pressure will quickly build up within a few minutes.

You can also use the pressure tester to locate the cylinder(s). Pull the plugs out and pressurize the cooling system. If there's a bad head gasket, one or more cylinders will fill with coolent.

It's not very often that you'll have a simple air lock in the cooling system causing the engine to overheat. Unless you have a fancy vacuum pump to suck down the cooling system the only other way is to create an air bleed. Somewhere on the highest point of the cooling system you need to have some way to vent off any air trapped. This could be something as simple as loosening a hose clamp on a heater line or installing a drain valve,

The top of my radiator sits lower than the top of my engine. I installed a drain valve in one of the ports in top of the intake manifold's coolent runners. When coolent comes out the drain valve I know the block and heads are full of coolent.

What did you do that makes you think you have an air lock? If you didn't have the engine aprt for any reason then I'd suspect the blown head gasket. An engine won't pick up a air lock in the cooling system for no reason.

 

I just re-read the original post. Passenger side valve cover is colder than the drivers side. Not very scientific but I'd say the passenger side of the engine or part of it is dead (plugs not firing because of coolent in the cylinders).

Try this. Use a timing light on each plug wire while the engine is running. See if all the plugs are firing. If a plug doesn't fire, the timing light won't flash.

I accidently left off all the plug wires on my driver side head one day. I fired the engine up and wondered why there was a slight miss under load. It's amazing that it idled fine on 4 cylinders.

And one last possibility. The thermostat is stuck closed. The hole you drilled won't have any effect if it's stuck closed.

 

well i think its air in the system b/c i just put a new motor in the car and changed heads,cam,intake and carb. 1 of the heads was cracked before so i had to ship both of them back for new 1ns...thats y i think theres air in the system,i never had this problem before.

as i said before, the car runs on ALL 8 CYLINDERS. it doesnt have a miss at all. it runs fine for a few minutes and then the temp slowly goes up to about 220,then starts goin up faster. today we bought some heater hose and im taking the heater control valve out and makin it alot simpler b/c the carb. and TPI heater hose routing is different...hopefully that will cure the problem.

thanks for the reply's folks

 

Did you re-torque the heads after the first heat-cycle? They say that one re-torque is enough, but I like to do it for 3 cycles.

 

no man,i didnt. i torqued them when i put them on the motor,but not after a heat cycle. ive only heard of that on aluminum heads but i guess it wouldnt hurt for a re-check even on iron heads.

but we figured out 2night that theres no flow of coolant after taking out the heater control valve and just putting hoses in the right place (the correct valve will come in tmw at Advance auto parts) and its still over heating. so im gonna pull the water pump off prob. tmw and see if i can find anything wrong w/ it. its a fairly new pump b/c i had to replace it when i first got the car about 1 1/2 - 2 years ago.

 

Aha! None of that was mentioned in the first post. My psychic ability isn't very good.

Do the new heads need a special head gasket? Is it possible that the new heads block off or restrict coolent passages in the block? I know on my BBC I had to drill extra passages in the deck to help cool the head better because of the head gasket I use.

Is the water pump regular or reverse rotation design? Is it spinning the proper direction? I'm assuming it worked fine on the old engine.

Since you're going to pull the water pump off anyway, pull the thermostat and check it. Boil a pot of water with the thermostat hanging in the pot. A thermometer in the water will tell you when the temperature is at the thermostat's opening temperature. If the thermostat fails to open at that temperature then replace it.