81 454 Suburban Overheating when Towing

[jcsmotorsport]

Hello,
I have an 81 Chev Suburban here in Australia and i am having some problems keeping my truck cool when towing. I can idle in traffic and not get hot but as soon as i load our trailer and tow the temp goes stright up , it runs consistently at 1/2 or a little over but as soon as we hit a hill it goes over 3/4 and almost to the red. We just went on a 250 mile trip with trailer and had to use heater to reduce the heat. Some say its an airflow problem , others say its a radiator problem and others say tuning. I had the radiator cleaned proffessionally but it did not help.

I am a little confused as to why it would only overheat at speed and with load on it.

Has anyone ever had a similar experience??

Truck is a 81 Suburban C20
454
T400
Towing a 25 foot race car trailer.

Thanks for your time

Jai Schluter

 

[crazy4offroad]

I would recommend an add-on transmission cooler. Since your current one runs in the radiator, once the trans gets hot so does the engine coolant. Welcome to the forum by the way!!

 

[bucket]

Well, since the radiator has been cleaned, you could start by adding on the tranny cooler and also checking your ignition timing.

 

[89Suburban]

Trans cooler, new radiator, bad thermostat, bad fan clutch. Few things to look at. Put in a new htermostat, cheapest thing to begin with, then a trans cooler imo.

 

[jcsmotorsport]

Forgot to mention that the truck already has a seperate transmission cooler.
What is the best way to check if the clutch fasn is ok ?
Tried a new thermostat also but no difference so i tried just using a milodon water restrictor instead of the thermostat.

Although the temp gets high the performance and tune still stays fine , Speaking of timing what is the recomended timing for a 454 ? Initial and total?

 

[Jims86]

Forgot to mention that the truck already has a seperate transmission cooler.
What is the best way to check if the clutch fasn is ok ?
Tried a new thermostat also but no difference so i tried just using a milodon water restrictor instead of the thermostat.

Although the temp gets high the performance and tune still stays fine , Speaking of timing what is the recomended timing for a 454 ? Initial and total?

Try to spin the fan by hand...If it stops immediately after you let go, the clutch should be good...if it freewheels, its bad. Factory timing is 4*BTDC
Also, make sure the Carburetor is nice and clean, just a little dirt in the jets, and you will run lean.
Check for vacuum leaks also.
What carberetor do you have?

 

[TheBigTater]

Check my thread on "overheating going uphill" just a few down from this one. I was having a similar problem with mine. I could drive around town just fine and idle in traffic all day and it wouldn't overheat. If I drove up a long hill even with a mild grade it would start to overheat. I posted some pics of the damage I found on mine. Pull the fan and shroud off for a good inspection. Pinhole leaks may be your problem.

 

[Camo]

how long has it been since you changed the thermostat and flushed the cooling system? If tis been awhile it probally needs to be done anyway. Not wasted money if it isnt the culprit

 

[WHEELMAN]

if your fan belts are dried out..they could be slipping..on the pulleys..when you put.some up hill drag on the motor..i had some slipping years ago.on a car..at idle you could not tell and they never made a noise.going down the road.

this worker at advanced auto he put a machine on there.to make the engine drag.and you could see the belts.just slow down and the pulleys..speed up..i went to another store and bought gates brand belts..

the cheap belts dry out look good.but they are so hard..they just slip.run a 160 stat.that will help..if the water pump is old..buy a new water pump.new one not rebuilt..retard the engine timing a little.buy higher octane gas..

 

[Camo]

I am curious as to what device they used to load the belts to get them to slip?

I have heard of belt slip from dried out belts, But usually a little dish soap will cure that till you can get new belts.

 

[78 K-10]

new thermostat, radiator cap. rad cap with 1-3 psi lower,every 1 psi lowers your system by 3 degrees fahrenheit. Any plated coolers for tranny or oil, ( I like and run B&m) new aluminum radiator, flush the cooling system. new high volume water pump

 

[bobehud]

okay this is an easy one
ok not the fan clutch once truck is at speed fan clutch is out of loop
even if a fan clutch freezes at speed sounds like an airplane

b rad is operating beyond its thermal capacity under load-forget cleaning
you will end up with the same CLEAN radiator that couldn't keep up

c what kind of RPM's are you turning at speed..??


if it was mine and i do own a 454-400 turbo burban get a 4 core radiator
180 degree thermostat.
also believe it or not if you don't keep your coolant change it will erode your impeller blades away.Had 2 trucks last year come in after the owner had replaced everything. 80% of the impeller had been eaten away..at idle or low speed it could keep up but under load at hiway speeds couldn't move enough coolant.

hope this helps