Got a problem

Hey fellas, i'm new to the site hoping to get some information and help out in any way i can...that being said, i've got an 87 iroc w/ a 350 tuned port engine. last week i was on the highway for about an hour or so and the car started to overheat...and ever since it's been overheating pretty bad. i replaced the water pump and put in a 160 degree thermostat...but it still gets pretty hot. could it be air in the system? or could it be a head gasket? i noticed a little bit of white smoke when it first starts up, not alot, just a little. it burns off pretty quick. i wired my fan to a switch so it's on most of the time, but it doesn't seem to be doing much cooling right now...it heats up alot quicker than it used to...also, at idle, in park, it has a frequent misfire...but when driving it seems fine. it's been doing this for a while now, just never paid too much attention to it. i'm not sure what could be causing this...maybe the head gasket again? i'm gonna check my timing and do a compression test tomorrow so hopefully i will know more then. any help / suggestions are appreciated...thankx

Does it run ok in town but get hot on the freeway? If so, check the bottom radiator hose, it should have a spring in it. If the spring is missing and the hose is old, it can get soft and the suction from the water pump will pull it shut (like drinking a frosty at Wendys through a straw, the straw collapses) and it will get hot. It usually will cool off when idling around town (the water pump slows down) if this is the problem. To check, just reach down and squeeze the lower radiator hose and see if you can easily pinch it shut and if it feels like it is starting to dry rot. If so, replace it.

Also, pull the dipstick, look for water in the oil. It will look like a chocolate milkshake if that is the case. If you see that, don't drive it until you get it apart (intake and heads off) to see where it is leaking or look for a "clean" spark plug, water in the combustion chamber will steam the carbon off the plug and one will be really clean in most cases.

That's the first suggestion.

Good luck!

I've stayed off the freeway since it started overheating, but it's been getting pretty hot just putzing around town. the upper and lower hoses are fairly new and the spring is still there. i made sure they were clear when i replaced the water pump a couple days ago. it seems to be pumping better than it did before, but it's just not cooling anything off. i pulled the dipstick and it looked like regular oil to me, but i'm gonna drain it tomorrow also and change it and see what that does. the plugs in it are about a year old, and i was planning on changing them, so they should have some carbon buildup on them right? if i get what your sayin, then if there's water in the cylinder, the spark plug from that cylinder should be clean right. ill check on that tomorrow also...thanks

New water pump? You didn't by any chance get one for a 88 and up car with a serpentine belt did you? Those are reverse rotation pumps and won't pump too well unless you have a serpentine belt setup on your car. Just another thought.

the pump has both serpentine and v-belt notches...the alternator is serpentine and the p.s. pump is v-belt. they sold me the wrong one at first, but i made sure the second time it was the right one, so i know i'm good there...but that belt set-up's kinda weird to me. why both kinds?

The dual belt setup was to make it more difficult for the alternator belt to slip and/or jump off the pulleys. The serpentine setup I was speaking of, drives the water pump with the back side of the belt and those are the ones that spin backwards. I wonder if they gave you one that was mis-boxed? Possibly? I spent many years working in a parts store and I've seen most all of the possible screw ups and that is one of them.....

The thermostat is not stuck or in upside down, is it?

I know what you mean, the mis-boxed part is what got me the first time. i ended up with a pump for an early model corvette engine...nothing like what i needed. but when i pulled the old one off, i took it in and made sure they were exactly the same before i left the store. if i pinch the upper hose, and then let it go, i can feel the water rush through the hose, so i know it's pumping good. i dont think the problem could be coming from a blocked hose somewhere else if it's pumping that good, could it? it seems to me that the most ovbious cause of this would be the head gasket, but then again, i'm not exactly a wiz when it comes to cooling systems either. i dont believe the thermostat is stuck open or closed...and it's spring down (into the manifold) correct?

The only difference between the reverse flow and standard flow water pumps (in many cases) is the impeller. You'd have to take it apart to verify which way it spins. I suspect it will pump some, even a reasonable amount of water while spinning backwards, but it may not work well at high speeds. I'm not saying it is your problem, but it is worthy of consideration.

I completely understand what you're sayin. If i can't come up with an answer or at least a general direction on which way to go tomorrow, ill probably end up pulling it apart again. ill give it a look if i end up doing that. thanks for the advice, any more suggestions would be great, i'm done for the night. Ill let you know what i come up with...Thanx

One more thing. You do have the plastic "air dam" that hangs under the radiator on the car still, right? If that plastic part is missing, they will overheat, almost guarenteed. It forces air through the radiator instead of letting it go under the car.

Just another idea.

Another possibility is if you have air conditioning,dirt and debree build up between the two radiators and can restrict the air flow. pull the top rad support and lean the rad back and clean anything lodged in between.

Did by chance lose or remove the Air Dam from the bottom of the car. The 6" by 4' piece by the bottom of the radiator. If it is missing it will affect the cooling.

Flush the block and the radiator with a garden hose, fill with new coolant. Try running it without a thermostat or buy a 160 from Autozone. Are both your fans coming on? You might have to hardwire them.

Also, check for that plastic airdam. The car will run real hot on the highway without it.

You're not using your AC are you?

Run a thermal scan of the radiator and see if it is clogged or if it is flowing freely. You should see a gradual temp drop as you go down. If you have a cold spot that might be it.

well good news, it's not the head gaskets after all. changed the oil and not a drop of coolant in it. also, we ran the compression test and had little difference between all 8 cyl's. so far as i'm concerned, the gaskets are in good shape right now. after we ran the compression test, i had him purge the cooling system of air, just to check if that was the problem, and guess what...it was. he did it a couple of times, and got all of it or the most of it out. it runs good now, with that 160 thermostat it's staying pretty cool. I think i'm gonna replace the radiator with an aluminum one anyways, only because the one in it right now is getting old, and i think it's got a small leak in it. thanks for all the suggestions, much appreciated.

Glad you got it fixed.

Have fun!