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Engine Temperature

Posted by toddnic 
toddnic Avatar
Todd Nichols
North Carolina, USA   usa
1977 MG MGB

I'm not sure if I have a faulty temperature sending unit or if it is normal to see as much fluxuation in temperature as I currently am. During the summer months I run between 1/2 to 3/4 on the temperature gauge but during the winter months the gauge is barely reaching 1/3, if that. Two things: First, I'm concerned if I am getting a correct temperature readout on the gauge. Second, I'm concerned if the engine is going to reach a proper operating temperature during the winter months.

Any one else have a similiar issue? Any thoughts.....

shughes Avatar
Scott Hughes
North Carolina, USA   usa

Todd, I rebuilt my cooling system last summer along with a new temp sending unit. I started getting much higher gauge readings than before rebuild. Finally to ease my paranoia I bought a relative inexpensive laser temp device to check my system under different conditions. Found that I have relative normal temp ranges for a RB car.
Might suggest the same to ease your mind or help troubleshoot. Easy to check system before, during and after drives to verify system temps. If you are sure the thermostat is operating correctly before driving then should help to pinpoint any potential problem areas. There are many factors that can affect running temperatures.
Likely culprit in my system is the temp sending unit. Newer ones from some sources have been identified to give off readings. Not so much a worry anymore as I know the system is working properly.



I haven't lost my mind.....I sold it on Ebay!


Kimberly Avatar
Kimberly ?
Pinole, CA, USA   usa

toddnic Wrote:
Quote: I'm not sure if I have a faulty temperature sending unit or if it is normal to see as much fluxuation in temperature as I currently am. During the summer months I run between 1/2 to 3/4 on the temperature gauge but during the winter months the gauge is barely reaching 1/3, if that. Two things: First, I'm concerned if I am getting a correct temperature readout on the gauge. Second, I'm concerned if the engine is going to reach a proper operating temperature during the winter months.
Any one else have a similiar issue? Any thoughts.....

What is the temperature rating of the thermostat you have installed?

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AVIMAX Avatar
Ryan Nadler
Toronto, Ontario, Canada   can

I had a problem for years with the reading on my temp gauge. In the summer it would read 3/4 to full hot. In the winter (the odd time I drove it) it would read normal. I tried a new sending unit and no change. A new thermostat and water pump, no change. A local british car mechanic (who may or may not be that good) told me that he replaced the voltage stabilizer, but still no change. Finally after looking at the voltage stabilizer and realizing that it was not attached to anything, just hanging off the wiring, I checked the schematic and sure enough it looked as though the housing needed to be grounded. I attached the unit to the firewall, and bingo! The guage works perfectly, reading just under 1/2 in the summer now, unless it is really hot and I'm in traffic, then it starts to climb. The only down side is now my fuel gauge never seems to reach full, almost but not full! But I can live with that reading a little lower than it should. Years of worry for something so small but overlooked.



BManBrian67 Avatar
Brian M
HB, California, USA   usa
1967 MG MGB MkI "MI MG"
2000 Porsche Boxster S "Got Box S"

DO YOU HAVE A THERMOSTAT INSTALLED???

You should!

B

toddnic Avatar
Todd Nichols
North Carolina, USA   usa
1977 MG MGB

Thanks everyone! I have a 165 degree thermost that I put in over the summer. I specifically put in the "summer thermost" to see if it would effect the engine temp during summer driving. No such luck! I'm going to check out a few of your suggestions. Hopefully a solution can be found!

MT-B Avatar
Matt T
New York, USA   usa
1959 MG MGA "Delilah"
1959 Royal Enfield Indian
1961 Royal Enfield Interceptor
1972 Opel GT
1976 MG MGB "Ruby"

Todd most people I know run a 180 degree thermostat year round.

I'm a little confused, you say "I specifically put in the "summer thermost" to see if it would effect the engine temp during summer driving. No such luck!" but your car is running in the normal range according to the gauge (1/2 to 3/4). So if it was running in the normal range during the summer with the standard 180 thermostat and now it is running cold, why don't you just change back to the standard 180?

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toddnic Avatar
Todd Nichols
North Carolina, USA   usa
1977 MG MGB

There is a 180 degree thermostat and a 165 degree thermostat. Some of the articles that I read stated that using the 165 during the hot summer months would help the car run cooler. You are correct in that I have not switched the thermostats back at this point but I had the same issue last winter so I don't think that the thermostat is really the issue.

DanN1DLH Avatar
Dan DiMartino
McDonough, GA, USA   usa
1976 MG MGB

Get one of those laser thermometers as mentioned in the earlier comment. They take the mystery out of the process. Harbor freight...around 10.00...accurate enough!

ourmg Avatar
George Heissenberger
Victor, New York, USA   usa
1973 MG MGB MkIII "OUR MG- The Old Girl"
2006 Mini Cooper "Greta's Mini"
2014 BMW MINI Countryman "Little Red"

Your readings are consistent for a "summer" or 160 degree thermostat. Typically in cold winter temps its hard to get the car fully up to temperature. a 180 degree may help or so will the old trick of blocking a portion of the radiator with cardboard.



"OUR MG" Glacier White 1973 MGB, owned since 1983. Factory hardtop. Member MG Car Club Western New York Centre
"Beer is proof God loves us and wants us to be happy" - Ben Franklin

AVIMAX Avatar
Ryan Nadler
Toronto, Ontario, Canada   can

Regarding the winter, I cannot speak from experience becuase I do not drive my car in the winter, but my dad had a '71 MGB back in '71 in Montreal and I remember him telling me two things he had to do in the cold. Every winter he had to block the radiator with a piece of cardboard, and he also had to add a battery warmer. But I don't think you'll need to worry so much in North Carolina, it's a little cooler in Montreal in the winter!

toddnic Avatar
Todd Nichols
North Carolina, USA   usa
1977 MG MGB

Thanks everyone for the advice! I just put in the 180 degree thermostat and blocked off 1/2 of the radiator with cardboard. I went for a 20 mile drive and the temperature gauge in the vehicle in 30 degree weather was registering about 1/2 way and with the heater on was just slightly below that level. Thanks for your help! I still am going to get a laser thermometer to get a precise check.

Thomas Lovell
San Diego, USA   usa

I've had the same problem. It worried me for a while but I noticed I was not smelling the normal hot engine stuff. (Oil and coolant) I got it to what I thought was hot and drove it to a very reliable mechanic who tested it with some kind of thermal lazer gizmo and his conclusion is that my guage is faulty. I've been trying to find a replacement but no luck so far. This is a part that I would want NOS not someones old one.

Let me know what you find you find out if it's different.

Later,

Tom

Lovellthomas@hotmail.com

mac townsend Avatar
Fairfield, CA, USA   usa

IMHO:

Visualize for a moment what a Thermostat actually does. (most folks, imho, do not really understand what it does or how it work)

Until the threshold temperature is reached (threshold being soemthing less than the rated value--rated value is when it is full open, not just partially open) it prevents coolant from leaving the engine to the radiator.

At threshold it starts to open allowing SOME coolant flow to the radiator. as coolant ion the engine gets warmer, it opens more. when coolant temp hits the rated value the stat should be full open and no longer has any effect on engine temperature. "Radiator, handing it over to you!"

If the conditions when the stat hits threshold are such that the radiator is being hyper efficient (like the ambient is cold) and the coolant is being cooled back down to, oh 30 degrees (ambinet) then the water returned to the engine, if any, is cold. and the stat may close back up but will then open slightly again when the jacket gets warmer. It will work back and forth like this until temp stabilizes.

A cool stat, like 160, will result in teh engine running cooler in cool/cold wether because the water jacket won';t be able to get to proper operating temperature. coolant is sent to the radiator at 150-160 but is retuend at 30-40 and that cools it back down

you do not want to run an automobile engine at 160 degrees jacket temperature. You want it at about 200 (which per std calibration on the B sender, is near H. H being 212 ideally).

So a hotter stat will move the jacket temp up because it keeps water in the jacket longer.

And, if the radiator is in good shape, there is no real reason to change stats for the season. I use a 195 stat in my '73 B all summer and rad temp is usually about 195-205..slightly over the rating on teh stat...which is as it ought to be. Well within safety for a 13 PSI system. If I replaced it with a 160 stat, it WOULD NOT lower the jacket equilibrium temperature but it would simply open fully sooner and the equilibrium temp would end up being within a few degrees of what is is with a 195.

This time of year, however, it would make a difference. and a cooler stat would mean a cooler jacket. Which is not really desirable.

if the rad cools too much (jacket does not get to about 1/2 or so), first block off the oil cooler if you have one. then block off about 1/3 of the radiator. cardboard with bungee cords works...or string or such.

Note that many diesel trucks have radiator covers visible on the outer surface of the grill this time of year...for the same reason





1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks: www.mgrescue.com

mac townsend Avatar
Fairfield, CA, USA   usa

Tommy Wrote:
Quote: I've had the same problem. It worried me for a while but I noticed I was not smelling the normal hot engine stuff. (Oil and coolant) I got it to what I thought was hot and drove it to a very reliable mechanic who tested it with some kind of thermal lazer gizmo and his conclusion is that my guage is faulty. I've been trying to find a replacement but no luck so far. This is a part that I would want NOS not someones old one.
Let me know what you find you find out if it's different.
Later,
Tom
Lovellthomas@hotmail.com

an aftermarket mechanical sender unit would work fine. summitracing has 'em

but...is it gage or sender? the gage only reports what the sender provides. unless the test mapped the voltage of the sender and compared that to the specs for the sender, there's no easy way to point the finger at the gage.



1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks: www.mgrescue.com

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