The Ford Barn

George49Ford · 08-04-2012, 08:17 AM

Going uphill the temperature gauge pegged hot. Pulled over with engine still running and it did not feel or smell hot. I've experienced an overheating flathead before and this one appeared normal, except the for the gauge. Gauge returned to almost normal on return downhill trip. I suspect one or both of the temp. sending units.

Is there a way to check the sending units and the gauge before I go replacing them? Engine is stock '49. Engine replaced as short block 10 years ago, Temp sending units are probably originals, and car was completely re-wired about 3 years ago.

Thank you for help and input.

Barry B./ Ma. · 08-04-2012, 08:43 AM

I had the same experience with the 51 sedan I had. In my case it was the right head temp.sensor. If I remember right if that one is defective the reading will double. I replaced with another and reading was normal.

V8 Bob · 08-04-2012, 08:57 AM

The single contact sender, usually on the passenger side, normally operates the gauge, while the double contact switch in series opens and sends the gauge full hot when the left side gets around 212 F.

George49Ford · 08-06-2012, 06:53 PM

Replaced both sending units. Temp. Gauge still shows hot but engine does not smell or feel hot. Any other ideas? Thermostats, pumps, radiator?

Frank Miller · 08-07-2012, 10:29 AM

I have a laser thermometer and when my gauge pegged I took different temp readings. The highest I recorded was at the sending units, which was about 220. It do not boil over and this was at the end of a long hill climb. It quickly cooled back down. My suggestion is to get one of these units so you can verify what is going on. I think they are less than $40 at harbor freight.

peewee2you · 08-07-2012, 12:49 PM

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George, had same experience, and had new wiring, new temp sending units, and replaced guage w/NOS and to no avail still pegged hot, yet water temp was right at 180 after a nice drive, but staring at that guage always made me uncomfortable because if it truly was having a problem, I'm not going to know about until it's steaming and visible or the engine is bucking and burning up. My cousin talked me into seperate mechanical guages and as reluctant as I was to add or change from originallity, it sure is a whole lot more peace of mind seeing and knowing what each side is actually reading.

ora masters · 08-07-2012, 02:03 PM

none of my gauges work on my 48 coupe put in all new senders no help i keep a log of my miles buy gas every 100 miles works for me and dont have to look at the gauges

Alaska Jim · 08-08-2012, 02:26 AM

my experience has been that most "new" original replacement temp sending units are junk. I tried several quite a few years back with no good results 3 were inop. right out of the box 2 did not read even close. finally pulled out my collection of temp sending units and tried untill I got the correct one to read right. there are #'s on the sending units that corespond (?) to certain years so that they match the proper gauge. I can't remember where I found this info, and have not been able to find my notes since I moved 5 years ago. I am sure someone here or on the other flathead site knows where to find it, pretty sure thats how I found out.

George49Ford · 08-08-2012, 09:48 AM

Thank you everyone for your input. I appreciate. And for Peewwee2you - You're right - It's really hard to ignore that gauge when it's pegged, even when you're pretty sure it's not hot.

George49Ford · 08-10-2012, 10:45 AM

Got a pair mechanical gauges from Napa. Easy to put in and they work great. Thanks all.

peewee2you · 08-10-2012, 12:47 PM

George, excellent move. Nothing like peace of mind. Enjoy the ride!

08-04-2012, 08:17 AM	#1
George49Ford Senior Member Join Date: May 2010 Location: Carson City, NV Posts: 179	1949 8BA Temperature Sending Units Going uphill the temperature gauge pegged hot. Pulled over with engine still running and it did not feel or smell hot. I've experienced an overheating flathead before and this one appeared normal, except the for the gauge. Gauge returned to almost normal on return downhill trip. I suspect one or both of the temp. sending units. Is there a way to check the sending units and the gauge before I go replacing them? Engine is stock '49. Engine replaced as short block 10 years ago, Temp sending units are probably originals, and car was completely re-wired about 3 years ago. Thank you for help and input.

08-04-2012, 08:43 AM	#2
Barry B./ Ma. Senior Member Join Date: May 2010 Location: Southbridge, Ma. Posts: 1,614	Re: 1949 8BA Temperature Sending Units I had the same experience with the 51 sedan I had. In my case it was the right head temp.sensor. If I remember right if that one is defective the reading will double. I replaced with another and reading was normal.

08-04-2012, 08:57 AM	#3
V8 Bob Senior Member Join Date: May 2010 Location: Granger (Northern) Indiana Posts: 1,520	Re: 1949 8BA Temperature Sending Units The single contact sender, usually on the passenger side, normally operates the gauge, while the double contact switch in series opens and sends the gauge full hot when the left side gets around 212 F. Last edited by V8 Bob; 08-04-2012 at 09:38 PM.

08-06-2012, 06:53 PM	#4
George49Ford Senior Member Join Date: May 2010 Location: Carson City, NV Posts: 179	Re: 1949 8BA Temperature Sending Units Replaced both sending units. Temp. Gauge still shows hot but engine does not smell or feel hot. Any other ideas? Thermostats, pumps, radiator?

08-07-2012, 10:29 AM	#5
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	Re: 1949 8BA Temperature Sending Units I have a laser thermometer and when my gauge pegged I took different temp readings. The highest I recorded was at the sending units, which was about 220. It do not boil over and this was at the end of a long hill climb. It quickly cooled back down. My suggestion is to get one of these units so you can verify what is going on. I think they are less than $40 at harbor freight. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

08-07-2012, 12:49 PM	#6
peewee2you Senior Member Join Date: May 2010 Location: Elk Grove, CA Posts: 663	Re: 1949 8BA Temperature Sending Units Sponsored Links (Register now to hide all advertisements) George, had same experience, and had new wiring, new temp sending units, and replaced guage w/NOS and to no avail still pegged hot, yet water temp was right at 180 after a nice drive, but staring at that guage always made me uncomfortable because if it truly was having a problem, I'm not going to know about until it's steaming and visible or the engine is bucking and burning up. My cousin talked me into seperate mechanical guages and as reluctant as I was to add or change from originallity, it sure is a whole lot more peace of mind seeing and knowing what each side is actually reading.

08-07-2012, 02:03 PM	#7
ora masters Senior Member Join Date: Oct 2010 Location: gordonville mo Posts: 519	Re: 1949 8BA Temperature Sending Units none of my gauges work on my 48 coupe put in all new senders no help i keep a log of my miles buy gas every 100 miles works for me and dont have to look at the gauges

08-08-2012, 02:26 AM	#8
Alaska Jim Senior Member Join Date: May 2010 Location: Palmer, Alaska Posts: 1,575	Re: 1949 8BA Temperature Sending Units my experience has been that most "new" original replacement temp sending units are junk. I tried several quite a few years back with no good results 3 were inop. right out of the box 2 did not read even close. finally pulled out my collection of temp sending units and tried untill I got the correct one to read right. there are #'s on the sending units that corespond (?) to certain years so that they match the proper gauge. I can't remember where I found this info, and have not been able to find my notes since I moved 5 years ago. I am sure someone here or on the other flathead site knows where to find it, pretty sure thats how I found out.

08-08-2012, 09:48 AM	#9
George49Ford Senior Member Join Date: May 2010 Location: Carson City, NV Posts: 179	Re: 1949 8BA Temperature Sending Units Thank you everyone for your input. I appreciate. And for Peewwee2you - You're right - It's really hard to ignore that gauge when it's pegged, even when you're pretty sure it's not hot.

08-10-2012, 10:45 AM	#10
George49Ford Senior Member Join Date: May 2010 Location: Carson City, NV Posts: 179	Re: 1949 8BA Temperature Sending Units Got a pair mechanical gauges from Napa. Easy to put in and they work great. Thanks all.

08-10-2012, 12:47 PM	#11
peewee2you Senior Member Join Date: May 2010 Location: Elk Grove, CA Posts: 663	Re: 1949 8BA Temperature Sending Units George, excellent move. Nothing like peace of mind. Enjoy the ride!