BearKiller

On my 89, the factory sender is located left-side at the fire-wall end of the block, sort of high, but not extremely so.

When putting a mechanical probe in that plug-hole behind the thermostat, it requires adding a couple fittings to get the probe above the thermostat.

On mine, I screwed a close-nipple into a hack-saw-modified continuously threaded coupling, screwed that assembly into the plug-hole, and screwed the probe into that.

A special one-piece extender is available to accomplish this, but they are quite pricey = something like $29 the last time I checked for a little 19-cent fitting.

I would like to keep my electric factory gauge operational, yet also relocate the mechanical sender to a lower location.

That location behind the thermostat is about the highest point in the coolant system, and will yield the highest readings, and in that regard, theoretically, should be the best location; BUT, as soon as the first tea-cup of water escapes, and a big air-pocket takes it's place, that probe is no longer sub-merged and ceases to yield an accurate reading; in other words, your engine can be quite a bit hotter than the gauge says.

CaptainChrysler

The stock sensor location is 3/4" NPT.

comptz

so does the probe mess with the thermostat if i used the adapter fittings that came with the gauge? The gauges i used are the 3 in one pod from autozone for $30. I am still confused on wether it messes with the thermostat.

GasganoFJ60

How long is the probe? If the probe is long and might interfere with the thermostat, could you install a sort threaded pipe, about 2 inches or so, into the block and put the thermostat on the top of the pipe?

Know what I mean?

Its like an extending sleeve...

The water table should be high enough because the radiator fill spout is much higher than the hole in the housing so you SHOULDNT have to worry about any air pockets getting in the extension and giving bad readings.

Thats the idea ive had floating around in my head for a while now cause I too want to install a mechanical gauge and still have my factory gauge work.

What ya'll think?

comptz

I know what you mean. If i remeber right(its already in the truck) ni think it was around 2 inches long if that.

GasganoFJ60

Well, have you had any cooling problems? If not, perhaps its not in the way, or at least not enough to notice...

comptz

i havent been able to run it long enough to be 100% for sure. I just know i can't get a darn reading out of the guage and i havn't been able to bleed it at that spot yet.

BearKiller

My radiator is a good four-inches above the gauge-sender and it still will trap air every once in a while.

It is not so much how high on the water-level it is, but the fact that it creates a trap with no higher outlet that is the highest point for air to go IN THAT PARTICULAR LOCATION. ??Am I making sense??

Otherwise, you could not push an up-side-down glass of air into the kitchen-sink and the air remain in the glass. ??Make sense??


If I can find no better solution to keep the probe better submerged, I am going to engineer a bleeder-valve into my fitting, such that air can be bled off without loosening the gauge-probe.

randyswelding

ok so where is the best place at the back,then

CaptainChrysler

12v 2nd gen's have a check valve installed in what we call the "bleeder hole". It is connected to the thermostat housing. It constantly purge's air from the system.

It is an upgrade I would like to do someday.

There is another 1/2" npt port on the drivers side on the head. Some where in front of the fuel filter boss. I can't find a clear pic of it though. Not in the intake plenum but under it, about the same elevation as the stock location at the rear.

BearKiller

I will have to check that out the next time I am close to a 2nd Gen.

That sounds like a good upgrade.



What is behind that plug; anything that might interfere with a sender-probe ??


I will definitely be checking that out.


Thanks.

CaptainChrysler

I don't know.

Didn't think about that!

GasganoFJ60

Ok, so a small air pocket can form there, If the probe isnt directly in the water, say an inch out of water flow, but still in the block no less, will it really read that inaccurately? And whats to say you cant bleed the air?

BearKiller

An un-submerged probe will be way off from the actual coolant temperature, at least fifty-degrees.

Bleeding the air requires the probe be loosened, the air-bubbles released, and the probe then retightened.