Jeepthing

Seen mixed info on this. Have a 5.3 swapped in a jeep tj and wondering if from the factory the electric cooling fan/s are shut off via a signal from the VSS. Having highway cooling issues and trying to look into every option.

Engine is fron an 05' Silverado, stock computer, modified harness, aftermarket radiator, full shroud, single electric SPAL fan.

Thanks!

oldgoat69

I don't think the fan shuts off, someone else may have further information. What do you have in front of the grill? Unless airflow is severely restricted at any speed above 30 mph you should have more than adequate air flow to provide cooling. If the fan runs at speed and you have a well sealed shroud you could be experiencing a damming effect at the fan. Silly question but which way does the fan push the air? Does it pull through the radiator into the engine bay or try to push through the core toward the grill?
What are you seeing for temps, low speed and at steady cruise?

Jeepthing

Air damming due to the shroud and fan is my concern. The fan pulls through the radiator and does great under 55 mph and 2K RPM. I have another thread for the high temp issue but didn't get any replies about fan being shut off at speed. I pulled the fan fuse and temps got up to 235.

I have a two core radiator with condenser and trans cooler in front. There is a winch and light in front of the grill. I will be removing the light as its a 20" bar that could be deflecting air. shroud is quite shallow also.

I don't want to double post so just wondering about the fan function, my other thread is in this section also.

Thanks for the reply!

TDMKR496

iTrader: (3)

The 2 core radiator could be your issue.

gofastwclass

iTrader: (2)

Probably the reason you have heard conflicting information is because the answer isn't a simple "yes, no." The answer to your question is dependent on several circumstances. If the AC is on, if the engine temp is above a programmed threshold, etc., etc. I realize the image doesn't show all the variables but, fan programming is one variable that is entirely possible to run or disable the fan at speed.

All this assumes a healthy engine that doesn't have a problem like a faulty injector creating a lean condition that only appears at highway speeds.

Settings from a stock 2005 Silverado PCM:

Jeepthing

I originally had a single core radiator and switched to the two core as the passages when viewed from the tank were pinhole size. The mfg thought coolant flow could be the issue so I swapped. What is your thought on the two being the issue?

Thanks for the pic of the stock computer settings. I notice that stock fan 2 doesn't turn on until 235, what is the max temp I should see on the highway??

gofastwclass

iTrader: (2)

On trucks there typically is no fan 2, but the logic is there because of cars using the same PCM. That setting is mostly for sitting idle or in heavy traffic, you should never see that temp on a good roll.

Max highway temp is another variable without an easy answer. Most engines in factory trim are equipped with a 195 + degree thermostat. The modern day logic is running engines hotter than we used to think was good with a carb engine for economy and emissions. Of course that was before home mechanics could datalog the engine and actually see what was happening and why.

In my experience, my cars always seem to run around the stat opening temp plus a few degrees when I review my highway run logs. If I do a WOT run or slow down the temp will rise, but steady state highway (50+ MPH) cruising stays near that number.

One thing that was only mentioned briefly is airflow or more importantly airflow control. You said you have a winch, lights, AC condenser and transmission cooler - that leaves very little open grille area. My question is are you hanging the coolers out in the air hoping air goes through them or are they ducted to force the air in a fashion you need it? Factory cars have very small grille openings and use lots of inconspicuous ducts and air dams to direct the air properly. This with a quality fan and shroud combination is arguably more important than radiator size (within reason). My 5.3 Thunderbird has a horizontal slit barely the size of both my hands laying flat, yet it stays in the 180 range all day long with the factory 140 HP V6 radiator. There was some "stupid ducting" I took out because it was broken or in the way when I first built the car, I couldn't get the temperature under control. I replaced the duct work and have been fine since. Every car I build I keep the existing or add ducting to keep things cool.

Since you appear to have a problem with temperature control while on the move, I would look into how the air passes around the accessories and through three coolers for your solution and not the fan.

Hope this helps a bit.

Jeepthing

All factory "ducting" is in place, however on a Wrangler that doesn't mean much. There is some rubber pieces in the grill on either side to help keep air going to the right place. There is another on the bottom side of the radiator. Winch was installed before the swap and never had an issue.

Something has to change, and I am starting to think several more changes still need to be made. Air and coolant flow both need to be improved I think. How to best go about the changes is the question...

Andy1

jeepthing,

I've read both of your threads, and I'll be interested in how this all gets resolved.

Air flow is very important, but one must understand how to get it. If air flow is your issue, your Jeep may be a challenge (there must be other successful Jeep/LSx swaps and maybe a search will get you to them...Jeep sites, off-road sites). In order to get air in, you must first get it out. If you are experiencing increased temps at speed (and taking into account what you've checked thus far), then perhaps the air is stalling as you go faster. Most people tend to focus on the inlet side, however getting the air out is hugely important. It's all about pressure differential. Just an aside; I recommended to a roadracer to reduce his radiator inlet area due to stalling, and much to his chagrin, his temps decreased. Now I don't suggest this would help in your case, but it is a very simple thing to try first. Moving on, the simplest, and most effective way to get pressure differential, is to create negative pressure on the exit side with adding a chin spoiler or skirt just under the radiator. The bigger the better. The way I tested this on roadrace cars, is by using cardboard. Clean the underside first. Cut to shape and duct tape in place (use triangular gussets for strength). You can add or subtract where you want....use plenty of tape. Pull to the side of the road, add a piece and try again (bring along a box cutter, cardboard, tape, and a small piece of plywood for cutting board). If there's no room directly under the radiator, don't be afraid to extend a flat tray back a bit, and then add the skirt. If you find success, you now have a template to duplicate it in steel or aluminum sheet.

This suggestion (test) assumes there's no other fundamental reason for your elevated temps. I'm making the above suggestion because it is very easy to try, costs virtually nothing, and takes little time and effort.


Keep us abreast of your progress.

Andy1

Jeepthing

http://www.highperformancepontiac.co...e/viewall.html

Thread above is one of the best real world test articles I have found thus far. I know it's not LSx based but the concepts are the same.

I think removing the shroud is one of my next steps. With the first (single core) radiator I added the rubber flaps to the shroud just like in the article, and the new shroud has "doors" but from my testing they don't open.

Thanks Andy1 for the post, appreciate it. With the factory seals on the sides I think I am set there. The top has nothing and I plan to add a seal between the hood and grill as well as a seal at the top of the radiator itself. The bottom is tougher and adding a skirt might not be possible. Adding vents to the inner fenders is a possibility and might help.

oldgoat69

How about posting a picture of the front of the Jeep, along with a couple of underhood shots, front and rear of the compartment. I seem to recall in the old days of SBC swaps issues with cooling due to the tight confines and poor heat exhausting.
Does the bulkhead get unusually hot at cruise? Have you tried running the heater to see if temp drops at all?

Jeepthing

I will try to get some pics and post them up. The engine fits great in the engine compartment but after all accessories etc are added there isn't much room for airflow.

gagliano7

My fans never come on at highway speeds 1992 chevy truck swap. You definately have an airflow issue. You may need a some kind of air dam like the older camaros so the airflow goes to the radiator instead of under the car.

Jeepthing

gagliano7 what temp do you run on the highway?

I can try to add a flat piece of rubber from under the bumper to as far back as possible under the Jeep. Adding an air dam isn't really an option on a Jeep that is heavily modified.

I did do some more testing last night with the "vents" removed from the fan shroud. Did seem to drop temps as the highest I saw was 219 under heavy load.

Relocating the trans cooler from in front of the radiator and condenser to the inner fender with its own small fan is something I will be doing in the next couple weeks. I am also considering adding some vents to the inner fenders to help get air out of the engine compartment.

Each small change I make seems to help drop temps a few degrees. Staying with this theme I think with a few more changes I can get things to a manageable level.