Hi all,

I recently did the inline thermostat mod since before the mod, the truck was getting up to 210 or so at most stoplights.

Since I have done the mod, the temps around town, stoplights, idling, and in cool temps have been great. 180-188 constantly.

However, when it is 90f+ outside and I am on a long uphill climb the temps are getting dangerously high at 215+. I turned around and started going downhill when I saw 220 and didn't let it get that hot again.

Replaced within the last 2 years / 10k miles:
1. Rebuilt Turner engine (long block) with new water pump
2. New Nissans radiator
3. Inline thermostat mod with 180 degree stat.
4. Peak 50/50 Prediluted Antifreeze and Coolant with water wetter added
5. Coolant temp sensor that sits on top of the engine

Pressure tested and drops from 18psi to 15psi but holds at 15.

Ive bled this thing 10 times at least by driving with heat on max / topping of the bleeder and raising the coolant tank up high and letting it run through.

I am about to try a severe duty fan clutch just to rule the fan clutch out. I know it fan shouldn't make too much of a difference when traveling at speed (which is when it is overheating) but it is a cheap thing to rule out.

QUESTION: One thing I noticed is that when cracking the bleed screw I hear a little hissing of air and then I can add a few oz of distilled water. I assume that this hissing is air being sucked into the system since it is under some negative pressure. Do other people experience this? I keep "toppping it up" by adding a few oz of distilled water but it keeps hissing and there is a little space for more water every time I drive it for long periods.

What else can I try? Any tips? I would like to get this cooling figured out, been battling for a while.

 

Stant 45358 SuperStat Thermostat - 180 Degrees Fahrenheit is the thermostat that I used in the inline mod.

Could it be restricting flow at uphill / higher RPM?

 

What speed are you doing when climbing the hill? Is there anything in front of the grill that cold impede air flow? Have you tested your fan clutch? Does your auxiliary electric fan work?

 

I have tried speeds anywhere from 50mph to 75mph, trying to see if increased airflow would help at higher speeds. No real change.

No it is the regular grill with the three or for rows. I actually removed the grill and and going to go for a test run today to see if that makes any difference. I have no lights or anything else mounted.

Aux fan works with AC on at idle, so that seems good.

Fan clutch does not free spin at idle. Fan clutch feels exactly the same when warmed up and cold though. When I spin it it spins about 1/4 turn (maybe 3-4 blades).

 

Stants are poo. Use motorad. Speaking from experience.

 

Doubt that is the issue but I can install a new motorad, getting desperate at this point.

 

Jason, the one I include in the kit is a motorad. The Disco radiator is a bit marginal for high load, been a long time since I had the kind of pull you are on but I know towing uphill mine will do the same. I did switch to the safari grill because it is worth about 5-10 degrees in hot weather, your grill removal test should confirm. At highway speeds I doubt that the fan or fan clutch has any impact.

Just to rule out any issues, you can also try the following:

1. Remove the thermostat completely, that will eliminate flow restriction as a cause.
2. Remove the hood seals at the cowl area - this is usually only effective at lower speeds but it is worth a test.
3. When you start the climb, switch from AC to run the heater, windows down, fan on full blast. This adds some cooling capacity and will confirm a lack of radiator capacity if it helps.
4. Try a climb in 3rd gear, that will speed up the water pump and flow through the radiator.

Unfortunately there are limited options for heavy duty cooling options for the disco. You can add the oil cooler from the early trucks, but that does not really add that much cooling capacity.

I am working on a heavy duty radiator mod, but it will likely be a few weeks before I have the prototype finished.

Good luck, let us know how you make out.

 

Fantastic, thanks for the help. The heater on full blast does help keep the truck cooler, I tried that one already.

Have you heard of anyone trying these Allisport radiators? I am highly interested in an upgraded radiator, that would be awesome if you could make one.

Also what do you think of the little plastic tray at the bottom of the engine? I have heard that might help?

Very interesting about the 3rd gear thing. If this can keep my temps below 210 in the severe cases I might just call it good. The temps are so good around town or when it is cool out, just these long mountain passes in high heat kill it.

Yeah my plan of action is this:

1. try severe duty fan clutch (with no grill)
2. remove thermostat entirely (and replace with motorad) any suggestions or a part number?
3. bypass the heater core as a test (just in case that is clogged or something)
4. Allisport or upgraded radiator of some sort.

 

Good advice about dropping it down a gear. Transmission don't like to be "luggged"...it creates a lot of heat internally (front pump on trans spinning slowly, not much fluid movement). Trans temps can hit 275/300 degrees and the trans cooler is mounted directly in front of the radiator...so...the super preheated air is flowing out of the trans cooler fins...right into the radiator fins. So, by downshifting...it gets the trans pump spinning faster, which moves more fluid and keeps trans cooler...which limits the amount of preheated air moving across your radiator.

l'd still check your fan, it should and will help, even at road speed if called upon. Next time it gets warmer than normally, 215/220 range, pull over, turn engine off (this part is crucial, and spin fan by hand...you should feel tons of resistance. It should not move more than an inch or two if working properly.

 

Jason, I forgot that you used the Meziere style inline housing, I think that uses the standard SB Chevy thermostat? Sorry I don't know the part number for that one in MotoRad but should be pretty easy to find.