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I notice that my engine temp was running pretty high(200-220 deg) So i installed a coolant recovery system. It helped prolong the inevitable high heat. Im using a 4 core radiator and electric fan. For years i ran with a 2 core radiator that i pulled out of a buick special. Engine temp with that setup was 250 deg on the hwy(4.56 gears/automatic) After doing some minor adj on the motor i took a test drive without the hood and the eng temp never rose above 180 deg. Has anyone encountered underhood temp problem like this? If so, what is a good solution?

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

250!!!!!!!

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If at first you don't succeed, try it like your wife told you to do it.

You can read this thread for more information. My 2-core is actually the equivelent of a normal 4-core because the passages across are 1.25 inches wide.

Last week it was 106F downtown and I drove from work to home at about 5pm. In stop and go traffic for 30 minutes my truck was running 170 to 180F with the fan on, depending upon whether I was stopped or moving.

When I finally got out of traffic I layed on the gas a few times and managed to get the temp up to 190F for a few minutes.

I wouldn't think you would need a radiator my size since your running a 6, but it wouldn't hurt to get close. I don't know if they make a smaller one off the top of my head.

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If at first you don't succeed, try it like your wife told you to do it.

The initial v-6 engine setup was a 3.8 odd fire, auto, 4.56 gears, clutch fan and the buick special radiator(250deg temp)Hwy rpm was 3500.
The current setup is a 4.1, auto, 2.60+/- gears, electric fan and a 4 core radiator(200-220deg temp)Hwy rpm is under 2000. I guess my problem is that too much heat is being trapped under the hood because with the hood off, the temp is very stable @ 180 and the coolant recovery tank got sucked dry(and im sure the system doesn't leak) It must be that there's not enough air flow thru the eng compartment. I removed the hood after a test drive and the hood was almost too hot to touch.

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Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Ben..What temp thermostat are you running? I'm running a 180. I decided to get the radiator rodded out and install a new water pump. I'm tired of this problem and i am determined to get rid of it. It's mainly the reason i elected to go with the 2.60 gear ratio. The truck still gets up and goes well so i'm happy with that but the overheating problem is still there although not as bad.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

160 t-stat.

From your list, I'm surprised your having problems. That setup should run at whatever your stat temp is at on the highway. I think there's something fishy going on. I think your headed in the right direction by rodding out the radiator and going with the new water pump.

Your underhood temp is going to be hot, but not unbearable. If the heat is radiating from your engine and radiator so bad that you can stand next to your truck without feeling like an ant under a magnifying glass, then I would think you have a problem with the engine itself.

Here's some other things to look for in random order:

Make sure you have the right water pump. Pumps designed for serpentine belts with a tensioner turn the opposite direction of the old v-belt style.

Check your ignition timing. Every motor is different but you should be in the ballpark of 10-18 degrees advanced at idle and it should go up to around 35-40 degrees if you rev it up to 3000 to 4000 RPM. Those are ballpark figures. That's with the vacuum advance disconnected and plugged.

If your catch can emptied itself, refill it. That means there's air in your system, which isn't good but it's unavoidable if you recently opened the cooling system or recently boiled it over. It's normal for the cooling system to use the coolant out of the catch can as it cools down and push coolant (or air) into the catch can when it's hot. This is why sometimes it's referred to as a reservoir. Once all the air bleeds out of the system it should stop sucking the reservoir dry. If you have to fill the reservoir more than a few times, something is wrong.

Make sure your engine is not running lean. Pop in some new spark plugs and check them after a highway cruise. Try to drive down the highway a few miles and then pull over and let the engine cool enough to pull a spark plug or two. The insulation around the electrode should be tan. If they look very light or even white, then your running lean and you need to richen up your air/fuel ratio.

A mechanical flex fan is the best for highway. Electric fans work good for city traffic. You may want to go back to a mechanical fan. This time ditch the clutch and just go with a good flex fan that's about 1 inch from the radiator. Get or make a fan shroud too.

If it still overheats then your radiator must be inadequate for the job. That means getting one that is larger or more efficient.

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If at first you don't succeed, try it like your wife told you to do it.

I pretty much covered all the bases you mentioned. Carburation in fact is a little too rich. Timing checks out and functions correctly. But the radiator itself is most likely the problem. When the engine is up to temp and the cap is off. Coolant level starts rising and falling. Enough to spill out of the filler neck. And when the eng is held at a high idle, the coolant level will drop drasticly. And when the throttle is released back to idle, coolant will spew from the filler neck. To me, this alone tells me its a plugged up radiator. The pump is trying to push coolant but the restriction only creates hi pressure, so the system tries to equalize by backing up thru the water pump. But the local radiator shops are closed on the weekends so i cant do much about it today. I'll let you know if it cures the problem

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Another tip, make sure your system pressurizes when you have the radiator cap on. The pressure is important to keep the water from boiling in the heads. With the cap on, you should get some pressure in the system after it warms up. You can check it by squeezing the radiator hose.

People tend to overlook or ignore this detail but it can make the difference. Even if the temp gage isn't over 212, in the heads it can be boiling in certain hot spots that are over 212. If the water boils, it turns to steam and expands, thus forcing away the surrounding water. Your temp gage is just giving you the average water temp.

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If at first you don't succeed, try it like your wife told you to do it.

Thats a good point!! Buick V-6 heads are inherintly prone to overheating(water jacket design, flow)I've already taken care of the water pump and now i must wait until monday to deal with the radiator. But the more i think about it, im certain it's the radiator. That night i drove without the hood, the temp stayed cool. The thermostat was hardly open and the radiator handled the minimal flow. Any cooling system thats working correctly should not spew coolant out of the filler neck, whether or not you rev the engine or not. With a plugged up radiator, im asking for hot spots in the heads so i should do this regardless.I'm also certain that the lower radiator hose isn't collapsing to restrict flow. My problem right now is keeping busy until monday.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Hey, if your married, don't let your wife know that your looking for something to do. She'll come up with a honey-do list that'll make your head spin.

I agree with you on the radiator too. Something is up with that thing. Let us know what happens when you get it back.

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If at first you don't succeed, try it like your wife told you to do it.

I should get the radiator back today. In the meantime, i'm curious to know if your still using those rubber skirts that hang from the fenderwells in the engine compartment. I'm considering removing them from the truck to increase air flow away from the engine compartment. Mine are not stock and they are old and crapped out.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

I got my radiator back and its back in. The temp reached 195 in around town traffic. 180 on the hwy. No coolant, just water in the system. I removed the rubber shrouds from the eng compartment and the hood temp isn't nearly as hot. The repairman said the radiator was 30 to 40% plugged so the work was worth it. The temperature in central Texas today was in the hi 80's. The real test will be when it gets into the 100's

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

Cool, sounds like an improvement. My skirts are long gone, but that's because of the wrap around header on the passenger side.

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If at first you don't succeed, try it like your wife told you to do it.

I am running a Buick 3.8 and I have found that these engines naturally run on the hotter side. My cure for the problem was a Howe cross flow aluminum radiator, electric water pump, Spal 16" super high flow electric fan and no thermostat. I was up in Redding this spring for cool April nites and cruised for 3 hours strait, and never got over 185 degrees.

Right now my truck is at the painters (on hold because of the weather).Before that, there was cool weather and the truck eng temp was very stable @ 185 F. There must be a 5 deg error in the gage itself. i can never get the motor to run any cooler under any conditions. Once i was going down the hwy, took an exit and came to a complete stop at the underpass. The temp spiked to 195 F. But quickly dropped once i was underway. It kinda startled me but i shouldn't let it concern me, The temp lives under 200 F and that is a blessing considering it used to live @220+. Im not sure whats going to happen when i install a carb thats more suited for this eng( currently a 650 cfm Q-jet) I can drive it but it swallows fuel and it will not tolerate the secondaries opening. Im not sure how its affecting the eng temp.

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

u didnt say if u have a spring in the rad-hose if u dont have ,id try that . i had 3.8, 4sp with 3 core rad it never got 180, but i had 160 ther-stat.id also be in 80d to 85 weather.

The hoses were replaced with the reworked radiator. I'm still running the 650 cfm carb. The temp gage element is located on the intake in the spot where the outlet to the heater core used to be. It's kind of placed in a void area now that the flow to the heater isnt there. The temp is always stable now at 185 F. I dont think of the cooling issue anymore. The temp is well under 200 F. I need to address the carb problem. It may have a significant influence on the cooling

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.

i feel for ya! ive had three different radiators and i push 195+ when it warms up. im goin aluminum in a few weeks. tired of messin around.

Its too stress full trying to flaunt your stuff when your worried about overheating. Am i right!?!

All last year i would take these little baby trips around the block. not go too far. make sure I was back and parked it 10 minutes. man, this year I want to DRIVE IT!

g

Did you read the first couple of entries to this topic? My first 3.8 lived at 250+degrees. That was stress! On the truck and me. I used to run the heater/defroster during the summer to try and keep the engine from melting. I was younger and i could tolerate such things. About a month ago i took the truck on a 200 mi round trip and it was great! Temps well under 200 F, and 70 MPH @ 2500 RPM on the open road. I worried for nothing on that trip. It was the big shakedown run for the truck. It sat still for 7 years and it just got the 9" Ford rearend(2.75 to 1). I just removed the axle to be reworked to iron out the vibration problem but i'll get it back from the shop mid week. It's never ran this cool or this fast on the Hwy. It feels good to have everything on the money and having an extra 1500 RPM at my command to go beyond the speed limit!!

_________________
Previous setup: 4.1 Buick V-6/TH 350
Current setup: 400 Small Block Chevy V-8/TH 350
9" ford rear end/short bed/blue
What do Water, Electricity and Humans have in common... They all travel the path of least resistance.