1995 S10 Blazer 4.3 (CPI) - vehicle is heavily modified, SAS'd, deleted remote oil cooler lines, top end rebuilt, timing redone recently, coolant is fresh, AC has been deleted, clutch/t-stat are working, fan shroud in place.

I drive it to trails around Colorado and at highway speeds not going uphill it runs ~190. I start having problems when I go up steep grades temps will climb 230-260 when it's 70+ out. On trails it usually hovers ~215 and that's running it pretty hard.

Considering putting in electric fans, cowl hood, or a remote oil cooler. Would an e-fan make much of a difference on coolant temps (considering I don't push oil through the rad w/ the delete), and running hot isn't much of an issue at idle? I also don't want to run too cold during winter months (which I think a remote oil cooler would do)?

Open to any and all suggestions that will greatly improve my temps.

 

I installed an aftermarket all aluminum radiator and recently upgraded the extra trans cooler. I had the radiator modified to accept the stock oil cooler lines. (See my build thread.) I chose this route since I was concerned with overheating while driving at highway speeds.

The upgraded trans oil cooler is one by Hayden that has a built-in thermal bypass valve to prevent over cooling. You might see if one of them will work for engine oil cooling.

If the Hayden coolers won't work, with a stand-alone oil cooler you can install a separate thermal bypass valve with it so that it will not over cool.

If your cooling issues issue when you are not moving fast, then electric cooling fans are likely a good idea.

 

I have the same aluminum radiator that Christine has, with Intrepid electric fans. My oil cooler is bypassed (filter mounted directly to engine block) and I have a manual transmission, so no transmission cooler. I never have any problems with running hot, whether crawling in 100-degree heat or pulling long grades in the summer with the A/C running.

Have you ever replaced the cooling fan itself. I know it sounds stupid, but I've seen a couple of times where somebody installed the wrong fan, so it was pushing air forward through the radiator instead of pulling it back. Worked ok at low speed but, at highway speeds, the wind was fighting the fan, resulting in little to no air movement across the radiator. If the fan is still original, that's obviously not your issue.

Nice rig, BTW.

 

FYI, to allow you to better consider if what I have done might apply to you, let me describe the origin of my cooling concerns. They originated with having to pull my boat, total weight ~2,200 lbs, up some of the steep grades near where I live. One is 1,900 ft in 6 miles where the temps can reach 100'F or more.

I burned out my 3/4 clutch-pack by allowing my transmission get too hot. I also like an idiot towed while in overdrive.

Something you might add that I added is a transmission oil temperature gauge. I found that this can be monitored through and OBD reader. I use one from Ultragauge. Using it I was able to see that my trans fluid kept below 200'F instead of going up to 220'F+ on that steep grade. The engine coolant temp also did not get as high as before.

As I write this, I find myself thinking about the effect of your big tires. This is likely a bit out in left-field, but with their larger diameter, the effective gear ratio of your axles is reduced which could contribute to pushing your engine and trans harder. Of course this would only be an issue if you were running a stock gear ratio.

Keep us posted on what you figure out.

 

This is for sure the root cause of my overheating issues. I have 3:31 gears w/ 36" tires.

Lower gearing is on my list.. but so are e-lockers. A little further down on that list is larger tires. But my rear axle is an AMC 20 and I'm pretty sure the lowest gearing I can get for it is 4:88.

Definitely looking for a band-aid fix to get me by.. but maybe I do just need to R&P swap.

 

Just to add my 2 cents on the e-fan swap, I'm running an Intrepid e-fan with a newer factory radiator. Previously when stuck in stop and go traffic with the mechanical fan my temps would climb to danger levels, I'd lose AC, and the mechanical fan would roar. With the Intrepid fan now I can be sitting idle in traffic or while crawling off-road in low range and my temps never change, and the AC stays ice cold. In my experience they do a much better job and are WAY quieter.