Yet Another Temp Problem

Hey guys,

I just recently purchased a '67 CJ-5 with the 225 Buick V6. The engine runs well, but I've got temperature problem. Within the first 5 minutes of starting the engine, the temp gauge reads hot (all the way hot). I've since changed the thermostat (180 degree), and checked the radiator for blockages (seems okay). The gauge still goes hot, though. Curiously, the engine isn't hot to touch even when the gauge says it should be. What am I looking at here?

I've tried searching the forums for a similar problem, but couldn't find this exact issue. I could be overlooking it, so if someone could direct me to the thread, I'd appreciate it.

Thanks!

 

Use a temp probe and see what the temperature of the coolant actually is. I have a multimeter for auto diagnostics. I'm sure there is something else not as expensive. Maybe even a cooking thermometer.

 

:iagree: Sounds like it could be a sending unit to me. What kind of temp gauge do you have?

 

It's just the factory gauge so far as I know. Looks to be original. I got a sending unit today and am going to try that out next.

 

That is what it sounds like to me. Let us know if that is what your problem is.

 

Well, got the sending unit in and cranked her up. It immediately went hot according to the gauge, in less than 30 seconds. Considering that's nearly impossible, I doubt the gauge is working properly. Is there something else I should look for? I let it run for 10 minutes while keeping a close eye on it. After the ten minutes, you could still place your hand on the engine comfortably. Even the lower radiator hose was slightly warm. Any suggestions?

 

has it ever worked? if it is reading wrong maybe the buick sending unit will not work with the jeep temp gauge. I would also check the wiring, maybe something is not hooked up properly. usually though if you wire the gauge wrong you will burn it out quickly. I would check the back of the gauge to make sure you dont have any additional wires going to it. on the older cjs there used to be a line out to the sending unit and the power came from a metal bracket that was attached to the fuel gauge's power. I found a diagram on the net once, this is the only one I can find now...it's about half way down
http://www.film.queensu.ca/CJ3B/Tech/FuelGauge.html

 

Hey there "hkmp5a2",

I had this exact same problem in my 225.

I went through the same procedures of checking the thermostat, then the radiator, then the wiring, bla bla bla... I even bought sending units form three different vendors just in case they were giving me the wrong ones.

I happened to be whining about this to a mechanic one day while he was working on my wifes SUV, he said the problem is the sending unit that goes in the 225 insn't matching up with the guage that's in the dash.

I guess it's possible that sometime in a Jeeps exsistance the previous owners will swap guage clusters or sending units, which leads to getting mixed up signals.

I know it sounds like a crazy theory, but I ended up using a sending unit for the V8. Since the V8 unit is larger, it took some creative adapting with brass fittings, but my factory guage is working like a champ!

 

Are you also losing coolant? Does the temp go down after driving? If so, it could be a head gasket. Had a similar problem in a 4.3L Chevy.

 

Since I've owned the Jeep (for about 2 months) the gauge hasn't worked properly. I'll check the wiring this evening and let you know. Also, I think I should check the fuel gauge's abilities as well. Since this is a project vehicle, I haven't had any significant amount of fuel in the tank and the gauge has always read "E".

So far as the sending unit not working with the gauge...I'm lost . When I ordered the sending unit, I ordered it for a CJ-5 with the Buick V6, thinking it would work. The gauge appears to be oem, with the speedo reading 0-9 for 0-90mph.

Also, I don't think it's losing coolant. The temp gauge remains hot when the engine is idling, but I haven't been able to get the Jeep rolling yet due to a stuck brake, which should be fixed by the end of today.

 

electric gauges operate on a specific ohm range. the sender has to produce within the ohm range for the gauge to be accurate. wrong senders can smoke a gauge with a quickness. sounds like the gauge is shot to me.

 

From what you have said I am pretty much sure it isn't an overheating problem. Sounds to me like a wiring problem somewhere or in the gauge itself. It could also be that you need a different sending unit. Try to trace the wires and check and check all connections.

Are you set on using the original gauge, or is switching to a mechanical gauge an option??

 

I was going to replace the original gauge sometime, I just didn't know when. I'll check the wires first, and if it comes down to it, I'll get another gauge. So far as the sending unit being the incorrect resistance, the sender I replaced looks exactly like the one I just put in, only older and grungy. I'll check on that possibility, too.

 

Here's a good dirt road simple check

http://home.comcast.net/~sday77/binky/repair_gauges.htm#Instrument Cluster Lamp Replacement

 

okay so here is my update...turns out in fixing my gauges the temp was fried...didin't actually read backwards like I was told..the idiot who installed them for me didn't take the insulator off the back so it didn't ground and sent the current through the system frying everything. What I read in the tsm is if the gauge never retracts and always reads hot then it is fried...if it retracts and reads hot check the wiring...the person that was working on mine installed 10 guage and when I rewired it I found that it called for 18. I am thinking that if it reads hot the other thing it calls to do is replace the sending unit...now one of the problems you may have is finding one the works with your engine and your guage...I would pull the one you have in the block right now and take it in with you to see if you can get a cj one for anything from 55-86 that is the same threading and diameter...good luck..I know from personal experience how much of a pain in the *** it is. Last thing to keep in mind...if you really need a temp guage...chances are you can look up what truck your engine came out of, find what type of guage it used, get an aftermarket one..and the guage of the wire to connect it to the sender and you should be in business...I know this is kinda the long way around things but sometimes you gotta get creative....last note...many auto stores sell aftermarket fuel and temp guages that are around the same size as your oil guage...so you install it a number of ways...holler if you need any help...and if you need cj guages you may think of getting them from 4 wheeler supply...they have a new aftermarket that installs easily and is less confusing to hook up..just keep in mind the grounds when you are wiring anything...the aftermarket and the oem both use an insultor that you have to take off the back when installing...so the guage grounds against the speedo assm..take care...Steve

 

here's one more solution...that you will probably like Just got my catalog for advance adapters (www.advanceadapters.com) and they have an inline temp sender adapter...so you plug in the adapter between your cooling lines and it allows you to use your stock jeep sending unit. Very cool option for anyone that has had an engine conversion...thought I would share...the part numbers if you are searching for them are 716673, 716673A, and 716674...take care..Steve

 

and another update....aftermarket guage I bought that was supposed to be for my specific year that I bought from a well known supplier of jeep goodies read just like yours. I turned it on and it went straight to hot...turned it off and the needle went back to cool. ran a heat test on the engine and it was not running hot at all, so I busted out the ohm reader and low and behold the gauges are calibrated wrong. I will post an update if I find someone who has a more accurate guage and let you know. so far I have had zero luck finding one that does not have the same problems.