Running HOT! ! !

[C20-67_N_MO]

Okay so I was at a fast food place today with my Suburban and while waiting in line I notice the temp gage getting way up there. I'm talking over 220 and slowly climbing!!

I know it's full of antifreeze and water when I replace my top hose I topped it off. It has the flex fan and no clutch at all. But once I got back on the highway the temp started to drop back to normal.

What should I do?

Flush the raditor or what?

Thanks.

[DANTIP]

Generally, when the overheating problem is happening at idle (very low load) and it goes away at highway speed (much higher load), the cause is poor air-flow THROUGH THE RADIATOR at idle. I assume you have a radiator shroud and it fits properly against the radiator. Also the diameter of the replacement (flex) fan is the same as the original that was designed for the shroud. A few pics may be helpful.

Dan

[C20-67_N_MO]

Originally Posted by DANTIP

Generally, when the overheating problem is happening at idle (very low load) and it goes away at highway speed (much higher load), the cause is poor air-flow THROUGH THE RADIATOR at idle. I assume you have a radiator shroud and it fits properly against the radiator. Also the diameter of the replacement (flex) fan is the same as the original that was designed for the shroud. A few pics may be helpful.

Dan

I'll see what I can for pictures either later today or tomorrow, as I drove the beast to work today.

And to answer your question, yes it has a fan shroud that fits tight against the raditor. Mind you this is an Oldsmobile 455ci engine in this thing too.

[BlackTopMotors]

Is this a recent occurance/has the 455 run cool before with the same set up?
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[C20-67_N_MO]

Originally Posted by BlackTopMotors

Is this a recent occurance/has the 455 run cool before with the same set up?
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I've just not gotten this running, (rebuilt transmission) so I honestly can not answer that question. Not sure if it has run hot in the past or not. Sorry, I know thats not much help but really don't have anything to base all this off of right now.

[Fldawg]

sitting still i would go with the flex fan, they don't pull alot air at idle

[C20-67_N_MO]

Originally Posted by Fldawg

sitting still i would go with the flex fan, they don't pull alot air at idle

Huh?

So are you saying the flex fan maybe why it overheats at idle then?

[Fldawg]

yes, never have cared for flex fans

[Sammy]

I think that is what he is saying.
Myself I'm not too fond of them anyway. If you are interested in changing it to a clutch type and get away from the flex fan we should have you come by my place as I may have something we can swap in laying around here if small block chevy stuff will bolt up. Best bet would be mounting electric fans which I could possibly supply you or at least head you in the right direction. Show you how Firedog mounted his maybe we can do something similar mounting a electric fan inside your shroud. Plus I could have some other ideas also. On a side note. You busy this saturday say 5-9 pm and want to bring it down to a cruise?? I will drive the 71 GMC. Still have finish touches on the 68 interior yet. His belts won't arrive till 14th and he needs door panel installation yet.

[MudBug]

I would recommend an electric fan for sure. I put two 14" fans on a friends 74 crewcab last spring and the truck runs at 190 all day long(185 thermostat) with a/c on, in traffic. I've never been a fan of flex-fans.

[C20-67_N_MO]

I gotta work 9-5 but anytime afterwards I am up to about anything. I freed my my window now but can't get it roll back up (and it's pouring down raining outside too, just my luck) lol.

I'll give you a call Saturday while at work and setup something with ya.

So far it looks like the flex fan doesn't fair well at idle. Hmmm that's something I never knew!

Originally Posted by Sammy

I think that is what he is saying.
Myself I'm not too fond of them anyway. If you are interested in changing it to a clutch type and get away from the flex fan we should have you come by my place as I may have something we can swap in laying around here if small block chevy stuff will bolt up. Best bet would be mounting electric fans which I could possibly supply you or at least head you in the right direction. Show you how Firedog mounted his maybe we can do something similar mounting a electric fan inside your shroud. Plus I could have some other ideas also. On a side note. You busy this saturday say 5-9 pm and want to bring it down to a cruise?? I will drive the 71 GMC. Still have finish touches on the 68 interior yet. His belts won't arrive till 14th and he needs door panel installation yet.

[6772owner]

I agree, I had the same problem with the flex fan the PO had on SBC, I threw it in the trash and got the original mechanical fan and clutch assembly and have never had a problem since. I also have the factory shroud and HD radiator (I think its 3/4 row copper) I have also heard that people have great luck with the Jeep Grand Cherokee fan in the factory shroud, there's a thread on here about doing it, pretty simple.

[Sammy]

Originally Posted by 6772owner

I agree, I had the same problem with the flex fan the PO had on SBC, I threw it in the trash and got the original mechanical fan and clutch assembly and have never had a problem since. I also have the factory shroud and HD radiator (I think its 3/4 row copper) I have also heard that people have great luck with the Jeep Grand Cherokee fan in the factory shroud, there's a thread on here about doing it, pretty simple.

LOL, yeah I just remember his driver is a Jeep Cherokee..I have a couple of fans here that might never know till the tape come out.

[6772owner]

Yea I know there is a thread on here somewhere with the Chrysler P/N to which fan it is, but Im pretty sure it was for newer (03+) models. It fits almost perfectly in the factory shroud and seems to be enough CFM on its own. Some guys upgrade the alternator as well, but depends on what else the truck is running electrically.

[Brock]

I had a olds 350 in my racecar. It ran hot all the time. I talked to an olds guy and he said to make sure the "steam holes" are in the head gaskets. He explained that replacement head gaskets may not have all the holes drilled in them and this WILL cause it to run hot. I didn't get to check, I sold the car. The flex fan is designed to "flatten" out at higher RPM; thus, reducing parasitic drag on the motor. At idle it should pull just about as much as a normal fan. My experience from dirt tracking is the radiator fins get full of mud, could your radiator need to be sprayed out?

[Stocker]

The only time my truck has ever run hot is when I ran a flex fan for a while. It has never overheated with a clutch fan.

[Sammy]

Never cared for a flex and after seeing what a failed flex can do to a hood and rad always made me be a bit leary. You will get responses from each direction on running a flex. But a failed clutch can also make a mess too. But so can a waterpump when it throws the entire mess thru the rad, which can happen. Electric seems to me to be safer as long as the rest of the system is as it should be. Allowing any motor to reach temps above 220 can't expect it to last long taking that sorta abuse.

[kevmic28]

I did the jeep fan install and my truck doesnt run over 200 all day long now.

[C20-67_N_MO]

Just sitting in travel today it the temp gague started to soar again!

I gotta either plurge for an electric or get a clutch fan setup. I'd rather go electric if I don't have to pay over a hundred for it. Get that and a switch and should be good to go right?

[MARKDTN]

Do you have a thermostat in it and is it a quality one? Do you have a 3 core or a 4-core radiator. You probably can't cool a 455 Olds-particularly if it has been bored-with a 3-row radiator.

[C20-67_N_MO]

Originally Posted by MARKDTN

Do you have a thermostat in it and is it a quality one? Do you have a 3 core or a 4-core radiator. You probably can't cool a 455 Olds-particularly if it has been bored-with a 3-row radiator.

The raditor looks HUGE so I am guessing it is a 4-row. As fas as the thermostat I am not sure. The way it heats up so fast I am guessing it has like a 190-195* in there.

That sounds like something I need to check into.

Thanks, as I totally forgot about checking the thermostat!

[Sammy]

By all means check the cheap thermostat first. Pull it if it's closed put it in a pan of true boiling water. If it opens it should be still good. Not sure if a single electric fan is going to do the job on that motor. You may need a pair of electric fans and a custom shroud that fits well. The rad shop in Desoto custom made a pair for me with a custom shroud on my rad removed and brought in. Includes a adjustable thermo that mounts in the drain cock believe they run close to $300-$350. So definitely a bit more than your wanting to spend for something custom. But alot cheaper than a ruined motor so go figure. I may have a clutch fan here that would fit but won't know till comparing it to what you have at the present as far as bolt patterns and room in your shroud.

[C20-67_N_MO]

I'd love to work on this on Saturday but I have to work all day. So unless I get up really early and get that thermostat off and check it, I won't be bringing it anywhere until I get this overheating problem solved.

And I agree, one lil' ole fan may not cool down this big berta of an engine. For right now I will like to try the clutch fan and see if that helps a lot. That and maybe replacing the thermostat with a 180* one.

Thats about all I can do at this stage.

[Longhorn Man]

ditch the flex fan, get a clutch fan.
I wouldn't trust my motor to a $100 china made electric fan, and would never want one run on just a toggle. Just forget it once and you have major problems.
Clutch fan hardly takes any power to freewheel... a horse or two, and when it kicks in, you need the cooling more than anything else so it's worth the few horses to get the airflow you need.

[6772owner]

X2, go Longhorn's suggestion and you will never regret it. If you go electric get a good system (Flex-A-Lite, etc), dont cut corners with the cooling system protecting your engine. Just my .02