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Overheating/ Diff Lock question

2K views 14 replies 8 participants last post by  CGunther 
#1 ·
I purchased my D90 last week. The first day I got it I was driving in the mountains and it started overheating and coolant was overflowing. I had to park it and the next day removed the thermostat. I had the radiator rodded, but the thermostat remains out. The vehicles temp gauge now sits after it warms up, right dead center of the temp gauge(except the other night it was about 50 degress and I drove down from Boone, about a 2000 ft elevation drop and the needle stayed over the cool part of the temp gauge.) My question is having the thermostat out, does this mean that the thermostat is Bad. Is the temp gauge staying in the center normal for a vehicle w/o a thermostat.

My next question is yesterday, I put the truck in 4wheel low, with diff lock. The truck started making an alarming sound, like a constant beep noise ,I reallly dont know how to describe it. When I changed back to Hi, or high w/ diff lock the alarm sound went away. Any input on this? Thanks
 
#2 ·
waht year is your Defender. Replace the thermostat with a new one, sounds like your old rad was clogged and you fixed it. where was the coolant coming from. what year is it and how many miles

Follow-up Post:

my temp gauge is about centered when its warm.
 
#3 · (Edited)
It is a 1997. It has 143000 miles on it. Im hoping your right.Im not sure where the coolant was coming from but I believe it was the overflow line where you put the coolant in at. Im not sure all I know is it was very alarming to see the truck smoke/steam like that.
 
#4 ·
The coolant probably came out of the dump line that is attached to the overflow can. It runs down the passenger side inner fender, and if it's hot enough will steam up pretty nicely. That may also happen once or twice as the system purges out air if you've flushed it or gotten really low and refilled it all. After you top it off, also check the level every so often for a couple weeks, in case it still has some air to burp out.

My old coolant gauge also stayed centered normally, but I have long-since replaced it with an autometer gauge.

-Hans
 
#5 · (Edited)
Put a thermostat back in.

the alarm is the warning that the transfercase is not fully engaged into a gear, which it may have been, just not to thehi/low sensors satisfaction. It is possible that the linkage needs a little lubrication, or just plain use, to get it working smoothly and to a point where the hi/low warning sensor works.
 
#7 · (Edited)
I'd hope you don't need a dealer ship to look at the t-case linkage. The best way to look at it is to remove the transmission tunnel.......er I just looked and you have a '97 with what must be an autobox right?

Try looking up between the frame and the transmission on the passenger side right above the rear of the front driveshaft. Have somone else operate the t-case shifter so you can see how the thing functions and then try lubricating the joints with some spray grease and then working that in.

If you still get the warning its possible that the warning sensor has gone bad or the linkage needs adjustment.

If it were my truck I'd rip the alarm buzzer's little heart out. But, if you've ever seen my truck or if yours is still "nice" we probably shouldn't start down that road.
 
#8 ·
OK, now the most recent issue, I have yet to put the thermostat back in , mostly because the parts store is having a hard time getting it, so the other night I thought I would take the D90 for a ride anyway, about an hour into the trip , while climbing a fairly steep mountain, the temp gauge raised to about 3/4- 4/5 the way to the hot side. Being this is my first D90, I dont know if this is normal.When coming back down the gauge went back to the half way point, and no other issues were noted a total of around 3 hr trip.. Any more Diagnostics from anyone. I am wondering should I get out while the gettings good on this D90 and maybe get another one. other than the heating issue it runs great, again being my first D90 what am I to expect w/ this vehicle. Thanks for the previous replies, they helped a ton, Thomas1997 Defender 90- 143k miles
 
#9 ·
The heat thing sounds normal. Mine gets just shy of the red when wheeling slowly down the trail. Last winter when I bought I would freeze my ass off. The needle would barely move over a 26 Km drive to work in -25C temps. It was also running very rich. Turned out my thermostat was stuck open. Changed it right away and now I have heat but in the summer it still gets quite hot in traffic. Not enough to worry me. Replace that thermostat quickly so you don't screw things up by running rich. The computer sees a cold engine and gives it way too much fuel for normal driving.
 
#11 ·
If the engine starts heating up under load, you might consider checking the viscious clutch fan? had a similar
overheating problem, I found that the clutch fan was deffective. It turned at idle, but would not engage at speed when
needed. The engine would overheat and the coolant would spill it's guts. After I put in the new one, problem was solved, the temp gauge is always just below the middle mark.
 
#12 ·
OK...so what temp is "just below the middle mark"???

Also: I've had two AC fan relays fail - the stock P&B branded and its replacement Tyco model (Tyco bought out P&B years ago). A non-running AC fan will get the gauge up there.

Since the 97 AC fan is switched by the ECU (and at a rather high temp) I'd be more comfortable with dual fans up front and a direct switch off the coolant,, in line with the stock setup.

Still though...a properly working system should not rely on an AC fan to stabilize temp. In the end I believe a more efficient, aluminum radiator is the way to go.
 
#14 ·
OK so I have replaced the thermostat, I allowed the truck to idle for about 30 minutes and the gauge was just below the half way point. I didnt get a chance to drive it yet though. Also I notice that after about 2 minutes of idling the gauge was already up to just below the half way mark, and the engine didnt even feel warm to the touch. My dad says that it may be a sending unit malfunction. Any ideas ?
Next I spilled some coolant so it smoked a little then calmed down. Then I noticed that after about fifteen minutes, every so often I would see a little puff of smoke coming from the back end of the right side of the motor. Ive heard that this is usually caused by a head gasket malfunction. Anyone ever experience this? I live near Boone, lenoir ,NC, anyone know of any mechanics that work on D90s close? Thanks for all the imput, Thomas
 
#15 ·
Check another post

There is a post titled !&*@! ..... still overheating!. Check that out. It is helpful for problem solving in this arena. I am about to post the solution to my overheating issues there. Sadly, it is a head gasket. Yours may not be however.

Boone is sweet. If I could find work there, I would be there. From Asheville originally. Dying to get back to the mountains.
 
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