During my 'collapsed lifter calamity', I took the opportunity to verify something that I encountered (and I know some of 'yall have too) when going to the FI Airgap..

Many users of the FI have complained, or at least remarked, that their engines run much cooler with the FI than they did with the keg.. I've asked, and most are relying on the dash gauge to determine this (which is, uh.. logical).. anyway-

I run an efan- and a temperature probe into the radiator for engaging the thing when a certain temperature is achieved. I noticed my dash gauge, and the radiator sensor for my efan controller weren't jiving on what the temperature actually was.. I explained this in a previous post, but I will again:

I drive the same route to work most days. I've grown accustomed to hearing and/or seeing a momentary drop in RPM's when the efans engage. That never changed after the FI, but the dash gauge thought I was running much cooler.. I set out to figure out what was going on..

I had an issue under the FI this week, and pulled it to fix 'er up.. While the FI was off- I checked out the bottom side of the manifold where the temperature sensor/sender is located.. I took a pic of it.. Later, while cleaning up, I pulled the 'ol keg out and took a pic of the exact same make/model sender that is still in it.. You'll see what I'm talking about below-


First, the keg-



that is the temperature sensor/sender's probe, as seen from the underside. It extends about 2/3 of it's body into the passage.


Now the FI Airgap:

Only about a quarter of the probe extends into the passage..

Sorry for the horrible pics- they are only passing good enough to show the difference, but the difference is pretty obvious, huh?

I'm thinking this is the reason why the 'gap appears to run cooler.. notice the 'appears'.. The truck is beyond doubt running pretty close if not precisely what it was before, but it's not getting as good a reading (or at least it's different) as/than before due to the majority of the sensor/sender probe not being exposed to the coolant...

 

where does that plug into on the airgap ? any way of makeing it a better read ?

that plugs into one of the coolent passages correct ? cant remember where that sensor is

 

Are you asking me to edit my post and make it more clear for folks w/o a gapper?

 

im just lost on where it is now on the airgap.

maybe email hughes about this with the pics and ask if this is the problem ?

 

it's to the left of the 'stat neck on the top.. Most of the sender's I've seen are gray in color.. It is a narrow two prong plug that is responsible for sending temperature readings to your dash.

The pic's are from the 'heads' side- or the bottom part that's bolted to your heads.. The brass probe is the actual sensor.

I'll fix the first post..

 

You think grinding down that slant on the inside would help any? I'm getting ready to install my FI Air Gap next month (left it at my bros house) And I'll let you know if there's any difference...if you can wait that long.

 

Dude, I think I know why my temperature reads so low.
So now I know that if the needle gets any higher than halfway between the mark above 130º and 210º that I'm overheating and need to pull over.

This is what it normally reads with the airgap and a 180º thermostat.

 

That looks to be a very likely culprit.

The fix would be easy if you have a die grinder. Just put a plug down the threads of the sensor hole as deep as you want to grind and slowly grind the spot open with a carbide grinder bit until you get to the plug. Just be really careful, as a die grinder will go thru aluminum like a weed wacker thru a warm dog turd.

 

Well damn. Sometimes the obvious just flies right past me....

On my FI, there are two temperature sensor ports. I used the supplied brass cap and blocked one (the one closer to center of the manifold) and used the one I knew he wiring harness would reach.

At some point soon, I'm going to pull that keg of mines sensor and put it in that second port to see if it gets a better temperature reading from there.

 

You can do that on a cold engine and as long as you drain the radiator, you don't have to pull a bunch of stuff apart so long as you can reach both the plug and sensor with a ratchet.

The manifold sits high on the engine and only the top of the radiator will graavity feed coolant out of the hole. The coolant in the top tube of the radiator wont drain back due to the closed T stat. You'll probably see very little if any spillage of coolant when you swap them.