He says he has an '82 engine in it, is there a change in the ohms the temp sender specifications between '66 and '82? If its more or less ohms won't that throw the gauge off? This still wouldn't address why it immediately jumps when he starts moving though.

Just a thought,
Seth

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Annabelle: 1970 Dodge Dart Hardtop
1991 Nissan 240sx (sileighty) Lots of mods
1974 Dodge Dart *Wrecked*

That depends completely on what variety of fan he installed. Some fans will move air equally well spinning in either direction. Some will move air at reduced efficiency when spun backwards. Some won't do much of anything if spun backwards. Most aftermarket fan blades I've seen will move air when spun backwards.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It is probably not a gauge/electrical issue. The gauge does not know or care whether the car is standing still or moving.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wow! A lot's happened from when I left this morning, thanks for all the input! Drove in this morning and it spiked hard to the right, came back half way and then continued to climb all the way while I was driving. When I stopped of course it would go back to halfway. Terrified as I was I continued. I pulled into work and left the car running pulled the cap off the radiator and stuvk my finger inside. It was steaming but not boiling. For some answers; The fan is a metal flex fan, and it is pulling air from the rad. The bottom hose does have a spring on it and I have never seen it collapse. Does it matter if the radiator cap is higher than the stat even when it is sitting level? thanks for all the input guys, I really appreciate it.

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66 dart 225

No, it doesn't matter that the cap is higher than the thermostat.

I am now beginning to wonder if it is a gauge problem, just not the kind we've been talking about so far -- could be a wiring problem behind the dash. Let's try some systematic diagnosis. There are three differences between standing still and moving forward:

1. The engine speed is higher when moving, and
2. The car is moving vs. stopped, and
3. There are vibrations present while moving but not while stopped.


Let's see if we can check whether this is really a moving-vs-stopped situation, or if it's actually engine speed related. Start the car, remove the air cleaner, open the throttle by hand, and swing the fast-idle cam into position (without closing the choke) so the engine is idling as fast as the topmost step of the cam will make it go. Let the throttle close on the fast-idle cam so it's sitting there running fast. Install the air cleaner and close the hood, then sit in the driving seat and keep an eye on the gauge. Does it spike? Or does it stay in the normal range?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

If you put a fan blade on backward, the pitch is still going to draw through the radiator, likely less efficently. By flipping it over, the pitch is still the same.

I would look for damage to the sending unit wiring. If it is tight across the valve cover and the mounts allow any movement, that could be the problem. If it is tight, splice a piece of wire into it so it is more relaxed.

When the engine torques over, it may be shorting causing the meter to spike high.

CJ

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Part of Tyrde-Browne Racing

I once had a short in my steering column when i put the car in drive sometimes my starter would engage with the car already running then i'd have to throw it into nuetral real quick to stop the starter from trying to start an already running engine. Could be some sort of short messing with the electrical when he moves the lever around to start driving the car?

Kev

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Lots of theories here, but no solid data.

It MIGHT be a problem with the cooling system (fan, hose, radiator, etc)
-or-
It MIGHT be a problem with false readings (gauge, sensor, shorts, etc)

We stand at fork in the road. Get more info before choosing which path to take.

Go back to Doc's suggestion and add a mechanical gauge to discover the ACTUAL operating temps.

Without that data, the last few posts (including mine) are just guesses. Good, helpful, educated guesses, but guesses nonetheless.

- Mac

If you have the car parked and rev it does it act the same as if you have gone for a drive (Like you have been) and it's over heating?

If that's the case then you should notice a under hood temperature change, check to see if there is actually a temperature change, an IR thermometer would be useful here.

I think it's more important to see if the car is actually over heating (Even though it doesn't seem that way from what you have said) then trying to diagnose a unknown problem.

Thinking of smaller more unlikely things here:
Did you clean our the gunk in the engine when you changed the radiator?
Is the belt slipping and the water pump not working the way it should when you increase RPM.
Did you check the new thermostat you installed?

Just my 2 cents, all these other blokes know alot more than me!

use meat thermometer to check real time temp of coolant.....it doesn't sound like you are overheating just getting reading you are

Hey guys, thanks for all I the info. I have ordered the thermo from ebay. Stopped by Auto Zone and picked up a mechanical Gauge, but it wouldn't fit. I temped out the radiator at less than 190. I don't think it is overheating. But it's driving me nuts. I will update as soon as I can. Again thanks for all the info.

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66 dart 225

Check resistance in the sending unit wire to be sure it is not grounding-out at some point.
Check the place were it goes thru the bulkhead connector & into the vehicle, contamination there can lead to this problem. A cracked, worn, oil soaked wire in the engine bay is another thing to inspect for.
This wire is a "controlled ground" so make sure nothing is "touching" the circuit "path" along it's route to the sender.

Which gauges does the voltage reducer behind the dash reduce voltage for?

The fuel gauge, and ... ...?

I can't remember. Too many Irish lattes.

Just trying to add a monkey wrench to an already stirring pot.

This morning I installed the mechanical temp gauge I bought on EBAY. Let the car run in my driveway till it reached right about 195. Thermostat opened and it cooled off. Sat there for 30 minutes and it operated right @ 198 or so for the entire time. Drove it around the block and then parked it, got out quickly and looked under the hood. 199. So it seems like it's ok. can you guys recommend a mechanical temp gauge that will fit in that hole? Thanks again for all the help. Now on to the exhaust leak!

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66 dart 225

I have never seen a mechanical temp. sender that fit a 1/8 NPT hole.
Just install the matching temp sender fitting into the thermostat cover.
Place it a little off-set, towards the outlet, so the sender "pod" does not hit the the top "bail" of the thermostat behind it.
DD