Hey guys.

I'm still having problems with my engine running really hot at idle and when tooling around town. Unless I can keep it over 30mph, my temp gauge keeps creeping up until it pegs at 280 in the red. I've never actually let it get to 280...I shut it down and let the fan run but still...it was headed that way.


I recently installed a new built 350 and that's when the problems started. Other mods are headers, World Heads, custom exhaust, a new (two years old) BeCool aluminum radiator for my year car, a jet fan swtich, 160* thermostat and my airdam is good. I also have a newer serpentine belt set up out of an 88 T/A but I bought a new water pump for an 88...so that shouldn't be the problem.

When I'm on the freeway or above 30mph, no problems, the car runs right at the temp it's supposed to. I even hot rodded it a bit on the freeway...never even hiccuped or got near 220*. However, as soon as I get in traffic or get stuck at a stop light the temp starts creeping up.

The fan does come on when it's supposed to at 185* (checked with external thermometer), and it pulls strong.

I burped the radiator three times to make sure all of the air was out of the system (might do this again just to make sure) but I'm really at a loss as to why it's doing this. Am I not pushing enough water? Should I check my coolant to make sure it's mixed right? Should I have the system flushed anyway? Does anyone have any ideas? Thanks!

 

Running the fan with the car shut down won't help--there's no coolant running through the system.

Wild guess: Do you have the correct water pump? Should be reverse flow.

JamesC

 

It doesn't help the car run cooler, just cools off what's in the radiator.

I thougth only the LT motors had the reverse flow water pumps? Would an 88 305 car have a reverse flow water pump? If so, then I need to get one that's not reverse flow...however, even if it was reverse flow, why would I be running cool at speed? Wouldn't it be getting hot all the time then?

I know the serpentine pumps have a reverse rotation compared to a standard V-belt type.

The block I have is from a 98 silverado with the vortec intake and heads (not running vortec on it now though). All my research shows that it should be the same as an older 350. Am I mistaken?

 

id check and make sure u dont have an air lock in your motor.
i had an air lock after i put my new thermostat in.
air locks do funky things mine woudent even cool down on the highway

 

make sure all your hoses are very tight because i changed my thermostat and that hose was just alittle loose and it was running hot den cool and back and forth then i made it real tight and it was running cool

 

I'll double check my hoses tomorrow. Could it be that my single fan just can't pull enough air to keep it cool? It was made for a 305...not a built 350. Still, I can't believe that it would be this bad.

Maybe I should have bought a waterpump for a 98 Silverado. /shrug

 

The water pump should be purchased to be compatible with your pulley system. If the pulley is smooth with no grooves & not a v-belt, it should be reverse rotation. If it has grooves for serpentine or is a v-belt, it should be standard rotation. More often than not, low speed heating problems tend to be air movement & high speed problems tend to be coolant flow related. If you do have have airlock problems, I would assume they would be gone by now with very much driving at all if your coolant recovery is working properly. Make sure your overflow hose is not clogged by blowing through it into the reservoir. Make sure your cap is functioning properly. If it has a dangling center rather than a spring loaded center, I always replace them as my years of cooling experience has shown me that "danglers" more often show up on vehicles with cooling system problems than spring loade ones do. Been watching & noticing this since 1981. Not that it doesn't show up both ways, but "danglers" go in the trash at my shop unless customer is stone cold broke when we are doing other repairs to the cooling system....Food for thought, good luck.....

 

The water pump I have is from an 88 T/A, it's identical to the one that came with the set up but after the alternator tested bad I didn't trust any of it so I bought a new one. It has a smooth center which means it's a reverse rotation.

Could it be that my single fan just doesn't pull enough to keep it cool?

 

Is it a stock fan? If so, stockers are notoriously ineffective.

 

I swapped in OE dual electrics and have experienced no problems whatsoever. Here's how I approached the swap:

https://www.thirdgen.org/forums/cool...electrics.html

JamesC

 

I have a single electric fan. It's supposed to come on at 185 (jet fan switch) and it does and it feels like it's got good air flow. Maybe it just doesn't pull enough to cool the new 350.

How hard do you think it woudl be to swap to dual electric fans and just have them both come on when the single one normally comes on now?

 

It is the stock electric fan. It is working as it was when I pulled my 305 which never ran hot. Then again it wasn't a built motor like this one is. could my new motor just be running so hot that the stock fan can't keep it cool?

 

i had that same exact problem excpet i didnt do any motor swaps and after a month doing the heat jump i ended up on the side of the road with smoke comming from the engine so i bought a new water pump took out my thermostat and got a brand new all aluminum radiator turns out it was my intake manifold gasket i guess it was leaking little by little untill i really did a number on it racing a turbo S2000.... dont know if that helps any but thats what was wrong with my 84 Z28 and we had the exact same problem so please let me know when u figure it out...

 

As soon as I do I'll let you know. I have already replaced my radiator with a direct fit repalcement from BeCool aluminum radiator. Mind you that was with the original 305 still in the car. Then I put a 160* thermostat in. On the highwya it runs right at where it's supposed to...160*. In town it still heats up. The water pump is new, I"ve exhanged coolant twice and burped the radiator many times...I'm almost positive that i"ve gotten all the airbubbles out. next will be the rad cap and maybe a dual fan from a later model TA or Camaro. WHich years of our cars had the dual electric fan? I've been looking on Rock Auto but can't find any.

 

im not sure when they started to run dual fans but i know whne i went to the junkyard i found a 91 firebird with dual fans all the other cars at the yard had a single fan i think i saw an 89 camaro rs and it still had a single...not sure though

 

i hate to suggest some bad voodoo but have you considered the head gasket leaking. I know you said you just had the motor build but sounds like a Radiator cap or head gasket. Try this tho to test the fans. If you have access to an air compressor run the car at idle as soon as it heats up help the fans with the compressor air. If it still runs hot check for some burbles in the resevoir, replace the radiator cap and then i think its time to check the head gasket. It could have been improperly installed. I'm no mechanic by any means but i've worked on alot of cars in my life. My Uncle who was a mechanic said the same thing sounds like a head gasket if the fans r working....

 

Turns out my fan switch connector broke where it plugs in to the sensor but was still "attached", just not making an electrical connection. For some reason it never occured to me to ohm out the wiring. (smacks head).

 

[I have an 84 z28 and its my 2nd same car and year. Ihave a new fan hot wired to run constantly. It takes a bit to warm up but once it is i have never had any running hot ir over heating probs since.QUOTE=Ozz1967;3979665]Hey guys.

I'm still having problems with my engine running really hot at idle and when tooling around town. Unless I can keep it over 30mph, my temp gauge keeps creeping up until it pegs at 280 in the red. I've never actually let it get to 280...I shut it down and let the fan run but still...it was headed that way.


I recently installed a new built 350 and that's when the problems started. Other mods are headers, World Heads, custom exhaust, a new (two years old) BeCool aluminum radiator for my year car, a jet fan swtich, 160* thermostat and my airdam is good. I also have a newer serpentine belt set up out of an 88 T/A but I bought a new water pump for an 88...so that shouldn't be the problem.

When I'm on the freeway or above 30mph, no problems, the car runs right at the temp it's supposed to. I even hot rodded it a bit on the freeway...never even hiccuped or got near 220*. However, as soon as I get in traffic or get stuck at a stop light the temp starts creeping up.

The fan does come on when it's supposed to at 185* (checked with external thermometer), and it pulls strong.

I burped the radiator three times to make sure all of the air was out of the system (might do this again just to make sure) but I'm really at a loss as to why it's doing this. Am I not pushing enough water? Should I check my coolant to make sure it's mixed right? Should I have the system flushed anyway? Does anyone have any ideas? Thanks![/QUOTE]

 

[/QUOTE]

You just bumped a 3 year old thread...

Running hot at idle?

you've burped the radiator?

Have you replaced your lower radiator hose?

Make sure you run your heater on full when you burp the radiator.




Are you running v-belts or serpentine set up?

Do you have the correct water pump?