So I took the van back to the dealer. I described the problem as: with the air conditioner off, the temperature rose to the top end of the normal range and the Check Gage light came on as I reached the top of the hill at 50mph. I did not hear any fan come on. I then drove a mile on level ground at 50, then turned onto a dirt road and drove 2 miles at 15mph. I never heard a fan, and the car did not cool to 210 degrees for about 20 minutes.

I suggested they block the radiator with a piece of cardboard to force the temperature up and force the clutch to work. The repairman says that the heavy duty fan does not have a two speed fan, but rather has a continuously variable fan. In addition, the fan will not run unless the car is moving. I had suggested he let the car get hot at idle with the radiator blocked to observe the reaction of the fan.

Does anyone actually know how the heavy duty fan is supposed to work relative to vehicle speed, temperature, etc? I need some help.

 

You don't have to be a rocket scientist to know that make no sense whatsoever.

 

I assume you are referring to the difference between standard, heavy duty, and severe service fan clutches. The short answer is that heavy duty and severe service fan clutches both spin faster, remain fully engaged at lower temperature (in my experience) and stay fully engaged for a longer period. The severe duty has much more surface area and this supposedly keeps it cooler so it should last longer. As a result, they use more horsepower than a standard duty but if you spend a lot of time idling or climb steep hills at low speeds regularly then one of these may might be a better choice for your application than the standard fan clutch.

This link may be helpful.

http://www.haydenauto.com/Installati...s/Content.aspx

 

Thank you. Great information.

So maybe its me! I drive about 9 miles on a road that climbs about 1600' in elevation. Has one 6% grade of about half a mile. I normally turn the overdrive off and drive at 55. At the top of this grade, there is about a 3/8 mile level spot followed by a 2.5 mile 6% grade (guessing). I use the 3/8 mile level spot to accelerate the van to about 50-55, then attempt to keep it at that speed up the grade. Would it be better for the vehicle if I drove it differently?

 

Do yourself a favor and replace the fan clutch

 

I did! (Or at least I think I did). I'll confirm today.

 

Is the van normally loaded to max capacity or is it driven more or less empty? If its loaded, I would expect this conversion to overheat a little on a 6% grade as its pretty heavy. If its empty, I don't think this speed or the way you drive is a problem. But I'd try it in 2nd gear at a lower speed (40 - 45mph) one time just to see if it makes any difference.

Are you absolutely certain the engine is overheating? Is the radiator boiling over into the overflow tank? Does the engine or exhaust makes crackling sounds (or any unusual sounds) after you arrive at your destination and shut it down? Because it is entirely possible that that your temperature sensor is going bad and the computer only knows what the sensor tells it.

The fan clutch was definitely shot based on what you've told us thus far. But its very common to experience multiple points of failure - and the resulting issue can be extremely difficult to diagnose without significant experience.

 

The first part is correct. The second part is not true of a working fan clutch, it always spins if the motor is running. However the engagement (how much it slips, how fast it spins) is supposed to vary with temperature. Its a *very* primitive part and doesn't really have any idea what your engine temperature is. It only reacts to the underhood air temperature.

 

One could agree and disagree with all of this, its just semantics. There are plenty of sources to quick learn how a viscuous fan clutch works. The important thing is verifying yours works. Again, multiple sources on this.

Replace the fan clutch and that doesn't resolve your problem then like Blackvan says, verify its actually boiling over. I wouldn't go by just the dash temp gauge. They are shoddy.

I agree with Blackvan, often multiple points of failure... or multiple weak points.

For instance, your radiator may not be considered a 'failed component' for a high percent of typical driving for your stock/chassis van. However, your's is a heavy modified van, has age on it, and is being put to the test in what some might consider 'severe service'. You could flush the radiator it all day and it'll never be good as new but that could be just fine for most scenarios, just not the one you describe. I experienced just about everything described in the previous posts (old radiator looked clean at filler neck but who knows how it really performs; fan clutch erratic; bad temp sensor, etc) and then some with my campervan. Ultimately I literally replaced everthing in the cooling system, most significantly an upgraded all aluminum 3 row radiator. Now the temp stays at 195 degrees (w/ a Stant 195) no matter what, even up miles long steep grades in the mountains.

The transmission on the other hand....that's a different story. If you put a trans gauge in, you'll at the temps coming out of trans pressure line while heading up steep grades, even with a brand new MOPAR rebuilt trans and new heavy duty trans cooler... but thats OT.

 

agree on a 3 row (nascar) radiator---expensive but does the job---ford and chevy rads are alot cheaper (imagine that!)