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  #1  
Old August 29th, 2015, 01:22 PM
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School me in cooling system

Ok - so over the last few weeks I noticed my stock water temp gauge increase where it would hold, right of center just to the left of the line depicting H.

After reading many of the posts here on the topic, I replaced the gauge with a VDO gauge to get a more accurate reading to ensure the system was ok. That said I don't know if I have the gauge set-up properly. I ran a dedicated wire from the new sender to the S on the gauge. I ran a new ground to the back of the binnacle and a new positive/switch-on wire. I got on the highway and saw the gauge creep higher than 210 and immediately turned around.

I pressure tested the system and the radiator cap and they both hold at 15pounds (using auto zone system). New cap on its was from RN any ways. Makes me hope its not head gasket or leak...

I have tested the fan clutch with newspaper and it chewed the paper up. I have also independently used an IR (cheap $40 home depot) thermometer on the brass temp sender and it shows 190ish.

Where I see the gauge really move is when on the highway and am cruising at 2800 RPM, however when I replicated the same 2800rpm with the pressure tester on and sitting at auto zone, it held the temp at 190ish. It really seems that the gauge goes over 190 when moving and not when i run it at 2800 in my driveway for five minutes.

Another note - whats crazy is I turn off the headlights and the gauge drops, turn them on and it goes up. Ive seen references to this and am at a loss on how to correct.

Possible radiator clog? Should I try a flush? I climbed under the truck to look for the petcock and didn't see one. Would be interested in hearing the procedure.

Also - whats the best procedure to burp the system? Take radiator brass bung off? 15lb cap? Id plan to run it with the front elevated. Should I run it at idle or at higher RPM? How do I know when done and what am I looking for - all air bubbles gone?

Seems like I'm missing something major and just can't see it through the fog. Im slowly trying to eliminate variables. As it could be one or many things. Sorry for so many questions, but would really appreaciate the help.
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  #2  
Old August 29th, 2015, 01:37 PM
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Are the hoses at the top and bottom equally warm to the touch and equally pliable? Are you sure yet that water is properly circulating and the pump is working properly? Have you tested your T Stat? By far the cheapest component to eliminate. I live in the area and have a spare pump from a 97NAS if you want to try swapping it out. I might still have a T Stat as well.
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  #3  
Old August 29th, 2015, 01:43 PM
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Yes - the hoses are equally warm to the touch. I have not changed the T-stat, but have an extra and may knock that out tomorrow. As far as pump goes, it isn't leaking, but I have no way of knowing if its flowing the proper gpm...
Also I have the 3.9 - do we have the same water pump? Thanks for offering I may just take you up on that.
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  #4  
Old August 29th, 2015, 01:49 PM
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Just to be 100% sure, ground your gauge directly to the negative on the battery. If the gauge is moving by turning on your headlights, theres something happening in your electrical connection somewhere. Where are you drawing your power for the gauge from?

You may be dealing with more than one issue here.
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  #5  
Old August 29th, 2015, 01:55 PM
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Quote:
Originally Posted by SimpleJack View Post
Yes - the hoses are equally warm to the touch. I have not changed the T-stat, but have an extra and may knock that out tomorrow. As far as pump goes, it isn't leaking, but I have no way of knowing if its flowing the proper gpm... Also I have the 3.9 - do we have the same water pump? Thanks for offering I may just take you up on that.
Ah, no, my pump won't work with a 94-95 3.9. I have been told that if the pump pulley is loose then it will not move enough fluid. This was my experience. At the same time I changed the Vfan, hoses and tstat. I had about 130k miles at the time and all my stuff was OE.
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  #6  
Old August 29th, 2015, 02:22 PM
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Flush will not do a darn thing but promote further overheating. Particles will loosen and fall to the bottom of the bottom of the tanks where normal flush will not remove them.
Furthermore, the residual chemical reaction is never neutralized thus after you button up the system particles continue to dislodge and clog your cooling channels.
Best approach new radiator, second best get the current unit rodded.
If it is the one installed from the factory I'm sure it is has been there a long time.
Once you stablished proper flow you may solve your issue or look somewhere else in the system for further concerns.
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  #7  
Old August 29th, 2015, 03:16 PM
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Thanks for all the tips. I think my next (easiest) course of action is to ground to the battery as Scott mentions and then see how it plays out. Thanks to all.
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  #8  
Old August 29th, 2015, 03:24 PM
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Quote:
Originally Posted by SimpleJack View Post
Ok - so over the last few weeks I noticed my stock water temp gauge increase where it would hold, right of center just to the left of the line depicting H. After reading many of the posts here on the topic, I replaced the gauge with a VDO gauge to get a more accurate reading to ensure the system was ok. That said I don't know if I have the gauge set-up properly. I ran a dedicated wire from the new sender to the S on the gauge. I ran a new ground to the back of the binnacle and a new positive/switch-on wire. I got on the highway and saw the gauge creep higher than 210 and immediately turned around. I pressure tested the system and the radiator cap and they both hold at 15pounds (using auto zone system). New cap on its was from RN any ways. Makes me hope its not head gasket or leak... I have tested the fan clutch with newspaper and it chewed the paper up. I have also independently used an IR (cheap $40 home depot) thermometer on the brass temp sender and it shows 190ish. Where I see the gauge really move is when on the highway and am cruising at 2800 RPM, however when I replicated the same 2800rpm with the pressure tester on and sitting at auto zone, it held the temp at 190ish. It really seems that the gauge goes over 190 when moving and not when i run it at 2800 in my driveway for five minutes. Another note - whats crazy is I turn off the headlights and the gauge drops, turn them on and it goes up. Ive seen references to this and am at a loss on how to correct. Possible radiator clog? Should I try a flush? I climbed under the truck to look for the petcock and didn't see one. Would be interested in hearing the procedure. Also - whats the best procedure to burp the system? Take radiator brass bung off? 15lb cap? Id plan to run it with the front elevated. Should I run it at idle or at higher RPM? How do I know when done and what am I looking for - all air bubbles gone? Seems like I'm missing something major and just can't see it through the fog. Im slowly trying to eliminate variables. As it could be one or many things. Sorry for so many questions, but would really appreaciate the help.
I hade the same problem, it turned out to be a grounding problem. 190 is normal in think.
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  #9  
Old August 29th, 2015, 08:23 PM
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So the ground to the battery helped and the needle doesn't move when the electric load change.

thermostat tomorrow. Thanks for the help so far.
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  #10  
Old August 29th, 2015, 08:37 PM
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but it doesn't end there...you have what seems like ground issues on another point. These things fail over time then it will be more of a pain. Best to resolve before those Va. winds start blowing cold...three months and ticking! Good Luck!!
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  #11  
Old August 29th, 2015, 08:51 PM
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Thanks Bill. Don't I know it. I'm just trying to get her in shape for the trip to Overland Expo East in early October. 1 month to sort it all out.
Any NOVA guys recommend a good radiator shop should I rod the radiator?
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  #12  
Old August 29th, 2015, 08:59 PM
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If you're concerned about the rad then replace it. I put a Nissen aluminum/plastic rad in my '99 D1. I also replaced the fan clutch at the same time. It is rock solid cooling in the slowest traffic and highest temps. Before I had to turn off the a/c and rev the engine in heavy traffic or at highway speeds. Well worth the investment of about $450 total.
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  #13  
Old August 29th, 2015, 10:22 PM
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The first thing I would check is if the engine is well grounded to the chassis.
As for cooling if the radiator is original it is 21 years old at this point so you might as well do something about that before you have real issues. John E just did this with his 94 and it took care of his elevated operating temp. This is also a good time to replace the hoses and belts since everything will be easy to get to.
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  #14  
Old August 29th, 2015, 11:21 PM
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Had the exact same issues - temp gauge, headlights, and all - and sought advice here. Everyone was very helpful and was grounding issue.
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1966 ECR Series IIA
1970 Series IIA (Stella)
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1989 RRC
1996 D1
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