Placement of temp sensor for cooling fan

[Brosky]

This topic received many posts and comments a while back. Today I happened to be talking with Bill at Ron Davis Racing about their custom built aluminum radiators due to a recommendation by TR6 Bill.

In any event the discussion brought this information to light.

They do NOT recommend the placement of the sensor in the radiator for several reasons.

1. using the radiator as a ground causes an acceleration of the electrolysis process and adds corrosion to the system very quickly.

2. the radiator is always much cooler than the block. The radiator doesn't overheat, the engine does, so they say to install the sensor in the head or block, but never in the radiator or hoses.

Now I agree that not all care for aluminum radiators and that the placement of the switch may very well have to be in either the hose or rad, but this is what I was told by the pro's, so I'm just passing it along for future reference.

Please don't shoot the messenger if you don't agree.... /bcforum/images/%%GRAEMLIN_URL%%/shocked.gif

 

[DNK]

I don't know if this is anything but my sensor is grounded to the front grounding block

 

[DNK]

Another idea
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box_bg_l.gif.
38MM FAN CONTROLLER
Click to enlarge

Description: At last a truly professional solution to the problem of controlling retro-fit electric fans on vehicles. Instant response; No interuption of radiator hose seals; simply installed in radiator hose. Temperature range control 70 C to 120 C.

Product: 38MM FAN CONTROLLER
Model: EFC38
Brand: REVOTEC
Categories: - - Electronic Fan Controller - COOLING

 

[Brosky]

Probably better than relying on the radiator, but which path to ground will it follow? Where it's mechanically attached or where it's wired to? I don't know.

When I asked for a sensor bung to be installed in the rad tank they flatly refused, which is what prompted the discussion.

 

[DNK]

I think it is not mechanically connected to the rad. So the only ground path would be thru the water. Unless it is grounded thru the body. am I lost on this one?

 

[Brosky]

I probably am. I thought that it would be threaded into the radiator bung.

 

[TR3driver]

There are different types of sensors. Some do ground through the threads, others do not.

Most of my non-Triumphs have had the radiator mounted in rubber, hence electrically isolated from ground.

 

[RonMacPherson]

Paul, electrolysis has been an auto industry problem for a number of years. GM, MB and Honda have all had tsb's or service information concerning this problem. Electrolysis will occur in any metal container that is isolated and has coolant flowing through it.

Most manufacturers recommend making sure that you do run a good ground path, clean bolt, extra ground wire, etc. to both the radiator and the heater core. I ran a ground wire, looping around the lower rubber pad on my radiator a loooong time ago.

Now he does raise an interesting and valid point about the sending unit locale. But just about every European and Japanese manufacturer for the last 30 plus years, have installed the fan control switch in the radiator.

I guess their presumption is that the radiator, running cooler, when it gets warm enough to trip the switch means the system is up to temp. Gotta remember that most of the German manufacturers fan switch comes in at a lower temp than our American manufacturers.

What I did when I put my webers on, was plug the manifold coolant hose exiting the back of the water pump, installed a fan switch there, had to put an adapter in as it is british thread(if I remember right) not standard pipe thread. Works good for me.

Another thing with running a ground path to your radiator is it will cut down on the natural electrolysis occurrence.

 

[Brosky]

Very interesting, Ron. More food for thought.

There's a lot of different ways to look at this.

 

[Guest]

It's ironic reading this thread - I was on the phone yesterday with the guys who are doing the tune on my car.

I had the coolant temperature sensor in a bung in the bottom of the radiator. I thought that was the optimal placement, and it seems that I'm not the only one.

It seems that that positioning wasn't accurate enough for the ECU. Instead they ran a sensor through one of the freeze plugs at the back of the engine (by brazing in a fitting). I have yet to actually see it, but they tell me that it works great.

 

[Brosky]

Gotta love it here. I learn many things every day.

 

[TR3driver]

It seems that that positioning wasn't accurate enough for the ECU.

ECU requirements are different than cooling fan ... it needs to know the engine temperature even when the thermostat is still closed.

 

[RonMacPherson]

Smokey Yunick was very interested in and relayed a lot of his learnings on temperature(s).

He did a number of articles for Circle Track magazine many years ago. Also in one of his books I believe he wrote extensively about the improvements in cooling passages and coolant flow for the small blcok chevy.

He was one of the first, if not the first, to advise placing the thermostat where it almost always is found on todays modern cars... Not at the upper hose going to the radiator.

One of the important things, I think, to remember is that there are actually several different temperatures that can and should be monitored for proper engine operation.

Any engine management control sending unit needs to be in the warmer part of the engine. Because we're focusing on combustion processes, as close to the combustion occurrences is the best way(cylinder head). As far as coolant flow, remember we're trying to remove the heat that is generated by the combustion process by transferring it to and through the radiator(cooling system).So in that case, you want to locate the sending unit where the most coolant heat transfer is occurring, or can best be monitored.

If you look at the water flow passageways of an early small block Chevy and the 6 head, they share a number of similarities. Early Chevy heads, when run in an all out performance mode would create hot spots where the coolant would actually boil inside the head and cost horsepower as the metal wasn't kept at the optimum operating temperature.

I did a little pencil planning around 18 or so years ago on how to modify the cooling system, following Smokey's guidelines, but other things cropped up(job, motorcycle, women, moving, etc) so never did follow through on it.

If you get an opportunity and can research Smokeys writings on coolant/heat control, I think you will find it immensely informative and interesting.

HTH, Aloha

 

[Geo Hahn]

To my simple non-engineer mind it seems that the relevant temperature for the operation of an electric fan would be the temperature of the coolant leaving the radiator.

 

[Brosky]

I guess that we could debate the "chicken versus egg" theory on this one.

Is it more important to cool the radiator coolant after it gets too hot from the engine overheating and is sensed in the radiator, or should it start cooling down the coolant in the radiator when a sensor located in the block or head sees the engine temperature getting too high?

Yet George has a good point in that you wouldn't want overheated coolant from the radiator being sent to the block, would you? But how did that overheated coolant get there in the first place?

This ought to keep it going for awhile.

 

[Guest]

I welded a stainless steel bung into the wall of the stainless lower return tube. Works for me. I also used a stainless steel sensor from Spal.

 

[Brosky]

That's what I thought Bill, but the other Bill, the guy from Ron Davis said no, put it in the block.

I'll probably flip a coin on this one. I really don't think that either way is going to cause me many problems for the amount of miles that I drive.

 

[71tr]

What about hooking into/replacing the temp sensor already located in the water pump housing, thoughts?

 

[2wrench]

Temp sensor to the block makes sense to me. As in,
what's going on with the engine? Oh, you're getting
hot? I'll increase cooling capabilities.

Not the mechanic, just seems to make sense.

As has been testified by respectable sources, I
conclude either would work in any case, especially
with the cooler-running radiator, simply because guys here says it works for them, and I believe 'em.

Just another question for thought: Does the radiator
come with a hookup for heat sensor?

Converesly, does the engine block come with heat
sensor hookup?

I suspect the radiator does not. If the block does,
though, it seems that would be the way to go...no???

Just asking, just asking...

 

[DNK]

Would the block drain be a possible location for a sender?