Nothing's ever easy . . . this one was supposed to be the reliable daily driver, too. . .

'89 rangie 3.9, essentially a complete new cooling system. Gauge still reading very high even after replacing the gauge sender. I don't trust the Lucas crap, so am installing an aftermarket temp gauge, guage is in dash, wires run, dash back together, everything nice and neat. Only problem is that the frigging sender won't fit in the tstat housing where the old one went. Autometer sells an adaptor which I got (5/8"), still doesn't fit and they're no help on the phone. I *think* the probe nut is a 5/8, though I've no idea what the thread is of the original sensor. If I can figure this out, next thing is even finding a fitting that'll work, I need a male to female, again with the female 5/8 I think and the male something else (18mm?). Any ideas before I drive this thing off a bridge? Oh wait, I'll have to push it off the bridge.

Tony

I'm not so sure you HAVE to have that temp sensor right there.

I think that it probably is one of the most accurate places to have the guage, because yeah, it's right at the heat source, but there are probably a few other places you could put it.

For example, you might be able to get a fitting you could splice into your coolant supply line to the radiator. The temp wouldn't be that dramatically different to make much of a difference (if any).

I think PTSchram did something like this, even left the guage under the hood.

Tony:
First off, not knowing the brand of gauge you have, it is difficult to say with any certainty what the thread on the probe is, although 5/8" is far from a common pipe thread-it is most likely 3/8" NPT.

On your '89, (I'm going from memory here and my '88 isn't in the lot), the sensor for the temp gauge is in the top of the manifold and is a british parallel pipe thread (as are most of the pipe fittings on these glorious trucks). I believe the sensor in the thermostat housing is for hte aux fans, rather than the temp sensor (running to look up the part number before I embarass myself further!). The older trucks utilized the plugged hole way down on the front of the intake so that port can't be used easily.

I have seen two different ways to accomplish what you are pursuing. On my truck, I cut the heater hose and installed a Tee with suitable fittings. On another vehicle (Ali's-perhaps he will chime in), the probe was fitted to the radiator plug.

Other than these two "Easy" methods, you may be in a position to drill out the hole in the intake (water jacket) to mate to the probe. Careful drilling and shop-vac technique will prevent the chips from going into the water jacket, although I doubt they would do any major damage should they enter the water jacket.

Peace,
Paul

Paul, thanks for the note. It's an Autometer gauge. The nice folks at autometer seem to think It's a 5/8 thread on the sealing nut (which thread's right into the housing) thought the "3/8" adaptor is too big by a hair to either screw into the housing or match the thread of the sealing nut. Somethings effed up. Sorry I misspoke on the location, it's just to the left of the housing, the sensor for the brain sits on top and to the right, aux fan sensor is as you say. Ideas on where else to mount it would be nice -- radiator is compelling as is one of the hoses. Where did you find the tee fitting?

Thanks again,

TB

Originally posted by ABrooks
Ideas on where else to mount it would be nice -- radiator is compelling as is one of the hoses. Where did you find the tee fitting?

Thanks again,

TB

LOL! Where else would I find such a thing? I made it! You should see the fittings I have for my Disco to allow me to drain the radiator without pulling a hose, nor the plug!

The drawback of the radiator location is that the capillary tube must be bent at an extreeeem angle, along with the necessity of finding and modifiying the threaded plug-while it isn't a big deal, some folks are put off by chasing threads and soldeirng things together.

I used the heater hose that comes out of the intake manifold, going to the heater core, rather than the heater hose that comes from the bottom of the radiator-it just seemed like the better place to sample. In the first iteration, I tapped into one of the hoses going to the expansion tank, but went to the heater hose as it is a more elegant design, less stress on the hose and the expansion tank-also, far more accessible should something happen and I would need to remove it from the circuit...

If I get a chance (a fat one!) this evening, I'll try ot snap some pics of my setup-it's not pretty, but it works andI know what the temp of my truck is. Having blowed up the heads due to not knowing what was going on and then, not knowing that my fan clutch was dying, having a gauge has proven its worth.

Who cares about pretty -- I'm using the side of a metal cabinet for a floorboard!

I found these adapters (http://www.spatechnique.com/store.asp?CategoryID=64&Category=Silicone%20Hoses%20and%20Accessories&SubCategory=Hose%20Adaptors&CustID=133054717) though the 25mm will be too large for the heater hose (which is 20mm I believe ID). I'm wondering if the bottom hose would be a good location for the sender. . . larger hose so one of these bling adapters would fit, but it'd provide an optimistic reading on the gauge.

I'd love to fab something up, but the truck's now been down for a week as I've screwed with this, and it's back to Chicago on Monday for another 2 weeks, so I need resolution on this fiasco.

Your heater hoses are 5/8", buy two brass hose barbs (less corrosive than iron) and a tee. On the short leg of the tee, bush it up or down to accept your probe. Parts should be available at Home Depot or Lowe's, if you don't have a lathe and soldering equipment.

I used the upper hose as it allowed me to secure the tee to the lower hose and not have it banging against the valve cover.

Paul

tony if you can give me the specs of everything I can probably make it in the shop here and mail it up to you in the next day or two. I have nearly everything here if you can figure out the tpi (threads per inch) and taper (pipe tap ect) and the size you want the pipe to be (i'll make it from brass we got lots) I"ll make it. Give me a call if you want 757-537-7676 I don't always answer (phone doesn't work on boat) but leave a message i'll get back to you.

-ben

You're the man, calling now. I owe you a fire extinguisher and a nurse to be named later.

TB

The first one to tell my wife I let a sale slip through my fingers dies!:flipoff2:

I'll send you a dick's picks to make up for it. Thanks!

A trip to the depot got what was needed -- 5/8" to 1/2" threaded barbs, a 1/2" tee, a 1/2" to 3/8" bushing with the Autometer adapter on top. It's butt-ugly but works perfectly in the heater supply hose. And even better, the truck's staying at 180 regarless of conditions. Lucas crap gauge is now disconnected. It's VERY nice having accurate information on the engine. Don't trust the stock gauge.

An additional mod you can do with that heater supply hose is to put a shut-off ball valve in line.

If you cut off the hot water supply to your heater core the footwell temps. are much more reasonable.

If you leave a very slight trickle through the ball valve you will still get a reading from your sensor to your autometer guage.

Originally posted by Serious One
An additional mod you can do with that heater supply hose is to put a shut-off ball valve in line.

If you cut off the hot water supply to your heater core the footwell temps. are much more reasonable.

If you leave a very slight trickle through the ball valve you will still get a reading from your sensor to your autometer guage.

This may not be quite as well advised as it sounds. Rather than just a shut-off valve, you "Should" divert the water back to the block, rather than just shunting it off. I am working on a valve that will do just this, but with a single, single-operating valve.

Somebody in my family does not like the hot air from the vents in mid-summer.

The early NAS Discos had a three port vacuum-operated valve to shut off flow to the heater core and divert it back to the manifold.

Actually Paul we have discussed this round and round on the RRO list.

The concensus was that if the water in the heater core was not circulated regularly that the decomposing glycol could potentially damage it.

The Saudi versions of the RR that do not come with a heater of any type just have plugs where the heater supply and return hoses are on our trucks, so just plugging it off is a factory option.

Originally posted by Serious One

The Saudi versions of the RR that do not come with a heater of any type just have plugs where the heater supply and return hoses are on our trucks, so just plugging it off is a factory option.

Do they have the nifty lower radiator hose that runs to the heater core from the bottom of the radiator? I suspect that there may be additional steps taken, other than just plugging the holes.

I vaguely remember having read a "Down in Tennessee" story about coolant flow. Having scrambled the top end of an engine from no coolant flow, I'm very leary of such things.

Curiously, the mirrors we market to the GCC are available heated. Why does a mirror with "Objects are closer than they appear" in arabic script come in a heated variation? Must be running in the mountains somewhere, eh?

PEace,
Paul