How/where to a install 2nd electrical water temp sending unit fj60 (1 Viewer)

[John McVicker]

'85 fj 60 stock & fullly smogged 2f. I want to use the stock gauge AND an aux electrical water temp gauge.

Wow ! I've searched until my eyes are red but can't find a thread that helps at all.

I want to install a 2nd water temp gauge (and keep using the stock gauge) and I wish to use an electrical one...not mechanical. It would be easy enough if I didn't want to keep using the stock gauge also...I've temporarily hooked up my new electrical gauge to the stock sending unit at back of the head and the aux gauge works fine.

What I can't figure out is what sending unit to get and even harder...how & where to mount it for the aux gauge. I've got to think someone smarter than me (leaves a wide field) has successfully done this. Can someone PLEASE point me in the right direction.

Thanks, John

 

[Output Shaft]

My thoughts on the matter:

I'm assuming you want a second temp gauge as a backup verification gauge when/if the oem gauge has its occasional schizophrenic moments.

Some guys have mounted another sender in a fitting in the big water outlet hose leading to the radiator. Usually the choice is mechanical, but those fittings can be had to fit any sender.

Although measuring temp down stream of the thermostat will not consistently give you the same readings as when taking the temp at the back of the engine, it is a lot better than nothing.

Usually when an engine starts getting real hot, the thermostat is wide open anyway, so the coolant temp flowing to the radiator reflects what is going on.

If the goal of a second temp meter is to verify a catastrophic loss of coolant and overheat from a blown hose, the inline mounted sender in the water outlet hose won't detect overheated coolant temp.... if there is no coolant flowing past it.

But one of those Engine Watchdogs will.

 

[John McVicker]

Thanks Output, and good point about the hose mounted sending unit.

As you 1st stated, I want to be able to verify the accuracy of the stock unit. So far I've had no reason to doubt my stock gauge, but it is 31 years old. It would be great if there is a easy to semi easy solution to a GOOD location for a 2nd electrical gauge ... 2 is better than 1.

Hoping someone has solved this issue & chimes in.

John

 

[John McVicker]

Bump.

Someone's got to have done this before...need help.

Thanks, John

 

[Jesper]

Check page 3 of this thread;
Radiators

In the photos you'll see a sleeve plumbed into the upped radiator hose with the temp sender plumbed into. Looks like a relatively easy mod. I've been wanting to add an aftermarket temp gauge as well but have similarly been stumped as to the best way to do it.

Not to hijack but I am intrigued by the engine watchdog---anyone have any experience???
-Would surface metal temp correlate closely to water temp?
-Which one would be most telling / critical to monitor if there was a difference?
-Where would you want to mount the sensor; lower block vs. cylinder head?

Looks like it might fit nicely in the usually-empty-sandwich-cubby-under-the-stereo spot.

 

[Output Shaft]

I haven't used the engine watchdog but one thing it will do is tell you if the outside of the head is overheating. They have a video on YouTube.

One problem with it that I can foresee is after shutting down a hot engine. The head gets real hot due to heat soak. We've all seen it when we start the engine back up a couple minutes later and the temp needle in the cab is almost to the max for a little while till the coolant starts circulating.

The Engine Watchdog has user settable temperature limits/alarm. You're supposed to set it beyond the highest temperature the head reaches after a hot shut down so it doesn't trigger the alarm at every hot start.

That temperature is pretty darn high, higher than I'd want my engine to get if I wasn't looking at the gauge.

But I suppose it could alarm for complete loss of coolant and verify if the oem gauge spikes into the red whether it's just a flakey gauge or a real overheat.

 

[John McVicker]

Thanks Jesper, good read. However, that's a mechanical gauge & I'm trying to use an electrical gauge. Also, based on what Output said, the sending unit location in the radiator hose can't detect overheat due a sudden/complete loss of coolant.

I'm hoping that someone has adapted a sending unit closer to the stock location, then we would have the best of both worlds...keeping the stock gauge, along with a quality aftermarket aux gauge.

Thanks, John

 

[txnight]

I tried hard to keep both the stock and afremarked gauges. Eventually drank another beer and went with only the aftermarket gauge. My stock gauge was inop so that made the decision a little easier.

The reassurance that comes with an aftermarket gauge is very nice. Good luck!

 

[John McVicker]

Yep, must be a reason no one has indicated how they've done it. Might have to go with just the aftermarket gauge.

Seems I always try to make things harder than they need to be. If it can't be done...it can't be done, but I wanted to try.

Thanks, John

 

[Kaasdief]

I have always like the idea of having an alarm sensor on the outlet manifold. Have never done it , but thinking about it.

 

[2mountainfish]

Is the stock gauge really that undependable. How many gauges do you have in your car. Could't resist John.

 

[John McVicker]

Your right, I really have no reason to doubt my stock gauge...other than the fact it's 31 years old. I actually thought that SOMEONE would have hooked them both up before.

Several years ago...and before I reconditioned my OEM radiator, I sometimes had my stock gauge get very high, it never pegged out, but it would have been good to see/know exactly what my real temps were. Or maybe scary...who knows ?

However, if we can't come up with a way to use them both, I think I will hook up the newer aux gauge up & use it instead of the stock gauge.

Still hoping that someone has a solution

John

 

[Spike Strip]

I have not done it myself, but I've seen where a local LC guru made a 'T' out of threaded brass pipe and used both the OE and aftermarket sender. The T was threaded into the stock head location.

I, though, preferred the mechanical gauge and put the sender in the upper rad hose. Works great.

I've also seen this if you have the rear heater deleted.

 

[doug720]

One concern with adding a pipe extension is an air bubble.

If the pipe is mounted vertical, air could be trapped and you would get an inaccurate reading. Horizontal mounting would be better with careful mounting so the sensor is lower than the outlet.

 

[John McVicker]

Ok Spike, now we're cookin. Do you happen to have any other pics of that install ? I can't picture in my head exactly what he did.

That picture looks to me like one electrical sender and one mechanical sender...no?? I'm trying to use 2 electrical senders.

Thanks, John

 

[Spike Strip]

Simple, just leave the OE sender in its normal spot and depending on what aftermarket you use, you'll either thread it into the fitting for the rear heater or you'll have to use an adapter. No more pix for that install. And that is a mechanical and it looks to me like the OE was moved to the heater union.

 

[2mountainfish]

Hey John, This is Jerry from Big Pine. What about putting a T in place of the stock sender and then putting a sender on each leg of the T. Just a thought.

 

[John McVicker]

Ok, at least we now have options. Today I hard wired the unit w/o actually hooking up to the sender nor mounting the aux gauge.

Will be out of the box for about 5 days. Will think about some of these suggestions and get back to it next week. Will try to adapt some of these thoughts...however, for the short term I will hook up the aux gauge while still attempting to get both working.

If any more thought please post up

Thanks, John

 

[Output Shaft]

None of those options shown or mentioned above are going to work very well. Sure, one was installed like that, but that doesn't mean it's very accurate.

The problem with the installation that is shown above is (as doug mentioned) the tall vertical riser fitting coming off the head to mount that sender. That's an air trap that will never purge and the sender will always be mostly dangling in air, not coolant. Small bubbles are always being created and flowing through even a pressurized system as spot boiling in the head is inevitable, and these pesky devils will collect anywhere there is a pocket... And grow.
Also that adapter fitting is much too tall.

Secondly, the rear heater has to be on all the time to have coolant flowing through that oem rear heater tee fitting to give an accurate reading. That's no fun. And just opening up a heater valve changes the flow through the back of the head, increasing it, which causes the stock sender to register lower coolant temps than actually exist in the engine, giving a false sense of increased engine cooling where none actually is occurring at all (overall).

 

[lovetoski]

Can you install the sender into the thermostat housing? Drill, thread, install?

I am desmogged, which means there are ports on the head to install an aux water temp sender (which I did). There's a pretty good correlation between the stock sender and my aux sender. Pretty good as in...the stock one is fine, on my truck at least.