Temperature hunting at stop lights

[1987R30]

I have a 1987 Chevy R30 (Dually) Standard Cab, 454/TH400+OD with AC, 3.73:1 final drive. 4 row aluminum radiator. 2 year old water pump. 180 degree thermostat. Original fan clutch. 60K miles. I'm in Florida (hot hot hot right now).

The temperature increases up to just under the 210 mark when I stop at stop lights. It drops down to just above the 180 mark while driving. I want that to be stable. What should I do:

1) replace the fan clutch
2) add a pusher fan
3) change to a hotter thermostat
4) something else

 

[gmbellew]

Does the shroud sit up nice and tight to the radiator? The shroud needs to be up against the radiator for the fan to pull the air through.

Is 180 the right thermostat? My 1990 350tbi runs a 195. Maybe 454 is different?

Also, the gauge isn’t always super accurate….you might be just fine at just under 210 on the gauge at a long idle. Actual temp might be a lot less.

 

[1987R30]

Does the shroud sit up nice and tight to the radiator? The shroud needs to be up against the radiator for the fan to pull the air through.

Is 180 the right thermostat? My 1990 350tbi runs a 195. Maybe 454 is different?

Also, the gauge isn’t always super accurate….you might be just fine at just under 210 on the gauge at a long idle. Actual temp might be a lot less.

Thanks. I'll check the shroud. The aluminum radiator was not an exact fit. I've ordered the 195 thermostat. And I'm not really using the gauge to determine temperature, but to see that it is hunting around when stopped in traffic.

 

[75gmck25]

Assuming the shroud and fan blades are good, it sounds like you need a new severe duty fan clutch, since your air flow is not adequate at slow speeds. However, temps in the range of 210 don’t really hurt anything. The threshold is around 230 before system pressure goes high enough to pop the radiator cap pressure release.

 

[1987R30]

Assuming the shroud and fan blades are good, it sounds like you need a new severe duty fan clutch, since your air flow is not adequate at slow speeds. However, temps in the range of 210 don’t really hurt anything. The threshold is around 230 before system pressure goes high enough to pop the radiator cap pressure release.

I thought the fan clutch was the problem too but it seems OK. I can hear it roaring taking off from a stop light and the fan itself will turn less than half a turn when spun by hand. I will look at it again to make sure it's not leaking or wobbling. I might even try the Hot engine test with the magazine. I just got a new copy of the LMC Truck Parts magazine

 

[Terlingueno]

Disregard...

 

[YakkoWarner]

I have the factory pusher fan on my Suburban (1989 3/4 ton with the 454). Clutches (like fans) are directional, are you sure you have the one that matches the rotational direction of your water pump? The wrong fan was on my Suburban when I got it, so I had to triple-check both the fan blade angle and the clutch rotation direction.

I have the TH400 without OD going into the 3.73 gears at the back - I didn't know you could get the TH400 with an OD! The temp stays in range while running down the highway but certainly creeps up at idle (my AC is currently INOP which is no fun in Texas summer). The pusher fans gets a workout for sure - I may have to look into a severe duty fan clutch myself.

 

[Rustisbest]

4 row radiator = air flow restricted at idle because they're thicker

 

[1987R30]

Down this way it is hot, 100°-110°F pretty much all the time May-October. K20 Suburban, 350/SM465, 4.10:1 final drive, non-functional AC, OEM fan shroud, Champion 3 row aluminum radiator, 195° thermostat, 120+K miles on the GM longblock (425+K miles on the truck). Temps at cruise hover around 200°. When I am at idle, it can go up to 210°. When I was in Death Valley (lots hotter than here), virtually the same on cruise/idle, 200°-210°.The stop and go traffic in Vegas (pretty much hotter than here) where I got groceries bi-weekly, sometimes the temp would hit 215° then back to 210° in a minute or two.

These temperatures are not on my 'worry about' list...

Im not worried about the temperature itself. I have a fairly new cooling system including the antifreeze. Im nowhere near blowing a gasket. What I dont like are the heating and cooling cycles. Im going to try the severe duty fan clutch. Maybe my old one is slipping ($60). Then, when that doesn't work, I'm going to install a 195 degree high flow thermostat (plus check my shroud as someone else suggested).

I have the factory pusher fan on my Suburban (1989 3/4 ton with the 454). Clutches (like fans) are directional, are you sure you have the one that matches the rotational direction of your water pump? The wrong fan was on my Suburban when I got it, so I had to triple-check both the fan blade angle and the clutch rotation direction.

I have the TH400 without OD going into the 3.73 gears at the back - I didn't know you could get the TH400 with an OD! The temp stays in range while running down the highway but certainly creeps up at idle (my AC is currently INOP which is no fun in Texas summer). The pusher fans gets a workout for sure - I may have to look into a severe duty fan clutch myself.

I have a pusher fan on my oil cooler. But not for the radiator. I bought the four seasons severe duty fan clutch from Rock Auto ($60).. It was sold out on Amazon. The rock auto link describes the difference between standard duty, heavy duty, and severe duty. I like that it engages at 80-90%. Maybe mine was warn out and slipping? I'll find out soon enough. But I will double-check the rotation. I think it said standard rotation. I can feel the air being pulled into the engine compartment. So I think the fan itself is correct.

The OD is an add-on. Made by gear vendors. I use it everywhere I go. My temp is perfect running down the highway. I use my AC every time I drive the truck. That would be the first thing I fix if it werent working.

 

[1987R30]

4 row radiator = air flow restricted at idle because they're thicker

I spent an exorbitant amount of time looking for a replacement radiator that had the same measurements as my original (including thickness)

 

[xm20k]

Stock gages are not accurate more of a close enough. Gives you an idea of what's normal and when something is starting to go wrong.

Even my Auto meter gauges float around 10 degrees, sitting in traffic vs driving etc.

 

[1987R30]

Stock gages are not accurate more of a close enough. Gives you an idea of what's normal and when something is starting to go wrong.

Even my Auto meter gauges float around 10 degrees, sitting in traffic vs driving etc.

This isn't the gauge's fault. It is clearly indicating a change in the temperature at stop lights and holds solid going down the highway. However, I do agree that trusting the value from the gauge may be subjective.

 

[YakkoWarner]

Im not worried about the temperature itself. I have a fairly new cooling system including the antifreeze. Im nowhere near blowing a gasket. What I dont like are the heating and cooling cycles. Im going to try the severe duty fan clutch. Maybe my old one is slipping ($60). Then, when that doesn't work, I'm going to install a 195 degree high flow thermostat (plus check my shroud as someone else suggested).

I have a pusher fan on my oil cooler. But not for the radiator. I bought the four seasons severe duty fan clutch from Rock Auto ($60).. It was sold out on Amazon. The rock auto link describes the difference between standard duty, heavy duty, and severe duty. I like that it engages at 80-90%. Maybe mine was warn out and slipping? I'll find out soon enough. But I will double-check the rotation. I think it said standard rotation. I can feel the air being pulled into the engine compartment. So I think the fan itself is correct.

The OD is an add-on. Made by gear vendors. I use it everywhere I go. My temp is perfect running down the highway. I use my AC every time I drive the truck. That would be the first thing I fix if it werent working.

I don't know the 1987 belt configuration, but on my 1989 I had to have a reverse rotation clutch and fan. If the water pump is driven off the smooth (no grooves) side of a serpentine belt, its likely to be reverse rotation water pump and therefore need reverse rotation clutch as well.

I looked up the gearvendors unit - nice but costs more than I paid for the whole truck so probably not getting one anytime soon.

 

[Rustisbest]

I spent an exorbitant amount of time looking for a replacement radiator that had the same measurements as my original (including thickness)

Was the original a copper/brass radiator? From what I understand the aluminum radiators have a higher fin count so the thicker they are the more restrictive they become. Supposedly the 2 row aluminum is equivalent to the old 4 row copper/brass. My own junk just has the parts store plastic tank ones that come on just about everything on the road nowadays

 

[1987R30]

I don't know the 1987 belt configuration, but on my 1989 I had to have a reverse rotation clutch and fan. If the water pump is driven off the smooth (no grooves) side of a serpentine belt, its likely to be reverse rotation water pump and therefore need reverse rotation clutch as well.

I looked up the gearvendors unit - nice but costs more than I paid for the whole truck so probably not getting one anytime soon.

I have two V-belts on my 87. So, I think I am standard rotation. I will confirm.

The gear vendors was expensive. $3K for the unit + $750 to have it installed + $700 custom drive shaft made. I could not use my 2-piece drive shaft per the GV instructions. The length between the end of the OD to the carrier bearing was too short according to the GV instructions. But, I got to step up from like a 2-3/4" diameter 2-piece driveshaft to a 3.5" diameter single piece driveshaft. I like that improvement a lot.