1968 300, any way to have engine temp lights AND a gauge?

WissaMan

Well-Known Member
Joined
Sep 12, 2018
Messages
533
Reaction score
524
Location
Northeast PA, 10 minutes from Knoebels Grove
I just finally got my gauges mounted and oil pressure connected. I want to do the coolant next. Am I going to loose any major amount of coolant when I remove the bung? I will do it when the engine is cold of course, but just wondering if I need to drain any coolant in advance.

This is OT, but my oil pressure sits around 20psi on low idle and 40psi at high idle. Does that sound pretty decent for an engine with 100k on it?
 

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
1,984
Reaction score
2,393
Location
Ponte Vedra Beach, FL
Am I going to loose any major amount of coolant when I remove the bung?

It's not that you'll lose a major amount of coolant, it's that it'll be a mess all over the place when you remove any coolant plug from the engine. Why not drain the radiator until it slows to a trickle and avoid all that mess and waste of coolant?
 
Last edited:

jct

Senior Member
Joined
Jun 11, 2015
Messages
3,742
Reaction score
3,766
Location
indianapolis
This is OT, but my oil pressure sits around 20psi on low idle and 40psi at high idle. Does that sound pretty decent for an engine with 100k on it?

as long as your oil pressure light isn't going off you are fine, cause i'm about in the same boat as you...
 

Gerald Morris

Senior Member
Joined
Mar 9, 2016
Messages
2,200
Reaction score
1,093
Location
Tucson
Drain off enough coolant to bring the level down below the thermostat; a gallon or so does fine. Then you can open that little 1/8" NPT plug and add in an electric sending unit there. I use a mechanical sending unit in the factory sending unit spot, and am thinking of using the 1/8" plug for a Normally Open switch set for 200 Fahrenheit. This will then ground my pusher fan relay, making a nice safety feature if I forget to flip the toggle switch for the same. I don't like letting my engines get over 200 F under any circumstance down here. 190 F is a GOOD running temperature for normal driving; less than that I see too much un-burned fuel in the exhaust, over 200 things get problematic, though I know with good coolant under 16 psi one can let things get up to 225F without much worry. Still with a cutoff at 200F, I have NO worry! :D
 

Gerald Morris

Senior Member
Joined
Mar 9, 2016
Messages
2,200
Reaction score
1,093
Location
Tucson
Indeed, you can buy a Dakota Digital guage that has the input screwed into those extra holes mentioned and it fits very nicely into the ash tray in my 1966 300. Since the ashtray isn't used any more you can just leave it shut unless you are concerned. It is very accurate and you can quickly learn how much speed, load, altitude and outside temp affects the engine temp.
Reach out to larrywjett@gmail.com if you want photos and details. I have put the guage in every Mopar I ever had because it is spot on correct. No need to add stuff under the dash.

Pity Dakota doesn't do C body dash sets. I like what they did for some of the B body stuff.
 

WissaMan

Well-Known Member
Joined
Sep 12, 2018
Messages
533
Reaction score
524
Location
Northeast PA, 10 minutes from Knoebels Grove
So today I attempted to install the sending unit into the little hole on the front of the water pump and.... the sending unit was just a little too big :( Not sure what to do now.

The gauge is an AutoMeter 2532 with electric sender.

Thoughts?
 

Gerald Morris

Senior Member
Joined
Mar 9, 2016
Messages
2,200
Reaction score
1,093
Location
Tucson
So today I attempted to install the sending unit into the little hole on the front of the water pump and.... the sending unit was just a little too big :( Not sure what to do now.

The gauge is an AutoMeter 2532 with electric sender.

Thoughts?
Find another electric sender that is exactly 1/8 inch NPT. If the 2532 is wedded too close to its sender, ditch it. OR, get one of those adapters that goes into the upper hose, and put the larger sending unit into that. 1.5 inches is going to be about 38 mm, which is the size these things are sold in, SI, not SAE. OR see if you can use a 1/8" sender w the old Mopar idjit light.
 

WissaMan

Well-Known Member
Joined
Sep 12, 2018
Messages
533
Reaction score
524
Location
Northeast PA, 10 minutes from Knoebels Grove
According to the item page on Summit, it states "Includes 1/8 in. NPT sender"
AutoMeter Traditional Chrome Analog Gauges 2532

But the sender didn't fit in that hole. Not just the threads, but the sensor portion didn't even fit into the hole. When I compared the plug and the sender side-by-side the plug was smaller. The car isn't here at my house where I can just walk over and check it again, but I'm 99% sure of it. Could it be that some water pumps have a smaller plug in that spot?

I'm not sure what you're referring to with the other suggestion of putting an adapter in the upper hose.
 

Ripinator

Old Man with a Hat
Joined
Jul 31, 2013
Messages
5,602
Reaction score
6,338
Location
Germantown, MD
According to the item page on Summit, it states "Includes 1/8 in. NPT sender"
AutoMeter Traditional Chrome Analog Gauges 2532

But the sender didn't fit in that hole. Not just the threads, but the sensor portion didn't even fit into the hole. When I compared the plug and the sender side-by-side the plug was smaller. The car isn't here at my house where I can just walk over and check it again, but I'm 99% sure of it. Could it be that some water pumps have a smaller plug in that spot?

I'm not sure what you're referring to with the other suggestion of putting an adapter in the upper hose.

EDIT: When I wrote the post shown below, I erroneously referred to the water pump hole I used as 1/8 NPT. It should have been 1/4 NPT. Sorry for the confusion. I fixed the errors. . .

Look again in the box the sender came in. I bought the same gauge, and mine came with an adapter that the sender screws into; then the adapter with the sender screws into the 1/4 NPT hole. Here is a picture of the adapter and sensor screwed into the 1/4 NPT hole on my '66 440 engine:

img_20180908_110844385-jpg.jpg
 
Last edited:

WissaMan

Well-Known Member
Joined
Sep 12, 2018
Messages
533
Reaction score
524
Location
Northeast PA, 10 minutes from Knoebels Grove
Ok, I brought both the plug and the sender home and tried them in a female 1/8" NPT thread hole I had here and they both fit.

So....why won't the sender go into the hole on the water pump? I am trying to put it in the hole that's on the front of the pump, not the one on the top like you have in your pic. Could it be that there's a crusty build-up that's preventing the sender from going in? I mean, the sensor part of the sender doesn't even fit in the hole, so the threads never even get close the water pump. If that's all it is, I have a 1/8" NPT tap that I can just run through the threads that should take care of that.

However, we had some concern that the sender might interfere with the coolant flowing through the passage. The plug is very stubby and doesn't protrude at all, but the sender has longer threads and the sensor portion protrudes about 1/2" past the threads. Anything to worry about?
 

jct

Senior Member
Joined
Jun 11, 2015
Messages
3,742
Reaction score
3,766
Location
indianapolis
I had the same issue as you due to crud build up. i cleaned it out with a small screw driver not sure i put tap through it
 

Ripinator

Old Man with a Hat
Joined
Jul 31, 2013
Messages
5,602
Reaction score
6,338
Location
Germantown, MD
. . .I am trying to put it in the hole that's on the front of the pump, not the one on the top like you have in your pic. . .

I'm curious. . . Does your water pump housing have a 1/4 NPT plugged hole? If so, why are you using the 1/8 plugged hole in the water pump and not the 1/4 one?

Here is a picture of my gauges during the recent break-in run on my newly rebuilt 440. I took this picture about a half hour into the run:

img_20181110_161545500-jpg.jpg
 

live4theking

Old Man with a Hat
Joined
Nov 24, 2014
Messages
12,057
Reaction score
8,089
Location
Rockland; Venango County Pennsylvania
I just finally got my gauges mounted and oil pressure connected. I want to do the coolant next. Am I going to loose any major amount of coolant when I remove the bung? I will do it when the engine is cold of course, but just wondering if I need to drain any coolant in advance.

This is OT, but my oil pressure sits around 20psi on low idle and 40psi at high idle. Does that sound pretty decent for an engine with 100k on it?
My father was a Chrysler mechanic when these cars were new. He always said that they will live fine at idle with as little as 7 PSI. That is wonderful pressure on a motor with 100K.

I'm willing to bet you'll find crude blocking the hole. I'de be leery about running a tap though.

I'm curious. . . Does your water pump housing have a 1/4 NPT plugged hole? If so, why are you using the 1/8 plugged hole in the water pump and not the 1/4 one?

Here is a picture of my gauges during the recent break-in run on my newly rebuilt 440. I took this picture about a half hour into the run:

View attachment 237936
Rip,
I've looked and I don't think our 68's have that port.
 

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
1,984
Reaction score
2,393
Location
Ponte Vedra Beach, FL
I just stumbled upon something in the FSM [Page 24-1] about the Cold idiot light regarding why it's there in the first place: You're supposed to wait until it goes out (about 110 degrees by my recent stovetop test) before you turn on your heater and freeze yourself. How brilliantly simple is that?
 
Top