Joined: May 05, 2005 Posts: 105 Location: Del Rio, Texas
Posted: Sat May 16, 2015 2:36 pm Post subject: Engine temperature
How hot should the engine get? OK, I'm not completely stupid, I realize engines get hot, very hot, even with propoper coolant, but is there a visual way to tell if an engine is too hot? I'm asking because it seems to me my engine is over heating. Yes, I have adequent coolant in the radiator. My temperature gauge appears to be working properly, the needle moves when ignition is turned on and it increases to about 170 after running for several minutes. But when you lift the hood you can physically feel heat radiating out from the engine, and if you spray water on it while running, instant, copious amounts of steam is generated. Again, I realize a hot engine is normal, but it seems to me it is excessively hot. If my temperature gage appears to be working, is there a way to check its accuracy? Is there a way to check that the water pump is actually circulating coolant? Am I being be too sensitive to these "older technology" engines?
Thanks,
Dan _________________ Dan
1951 M38
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Sat May 16, 2015 4:23 pm Post subject:
Hi Dan,
With the engine cold, remove the radiator cap and leave it off.
Start the jeep normally and allow to come up to normal temp.
Monitor the liquid in the radiator neck. It should begin to move
around a little , and you can stick your finger in and feel it warming
up.
Once the fluid gets to the temperature required to open the
thermostat it will open, and you will begin to see the fluid
moving from one side of the radiator to the other.
That is the water pump moving the fluid from the engine
through the radiator and back.
If the engine reaches operating temp and you do not see
any fluid movement you probably have a bad water pump
or thermostat. One is infinitely less expensive and less of a
pain to replace than the other.
Just be aware that at some point if you reach to 212 degrees the fluid
in the radiator can get warm enough to come up and out of
the radiator top. Keeping the fluid from boiling is a function
of not only antifreeze/coolant but pressure as well and with the
cap off you've taken one of those out of the equation.
Never trust a 50 year old electrical gauge. Always keep a pair of mechanical gauges you can use as a test set. One for water temp and one for oil pressure. Every old jeep I have ever restored with electrical gauges I have always made the first startup with a pair of these mechanical gauges substituted for the correct electrical gauges. When I am satisfied all is well then i pull the mechanical gauges and hook up the electrical and compare readings. If there is a significant error in readings you can bet that 99% of the time it is the electrical system that has the error.
Joined: May 14, 2009 Posts: 971 Location: South Dakota
Posted: Sun May 17, 2015 5:27 am Post subject:
Two simple ways: infared point and read thermometer, or if you are careful, open up the cap on the radiator and immerse a candy making thermometer into the antifreeze that you see moving accross. The engine is returning the hot antifreeze out of the block to the top. Pulling a hill with your Jeep can reach 200 degrees commonly. Going down the other side, it should cool back down to near the rating of the thermostat. Drain some coolant down in the radiator while it's not running and cooled off. Look in with a flashlight at the tubes of the core. If they are full of junk, You found your problem. John
The simple way will not give you the long haul picture. Use the mechanical gauges and drive the jeep so you can see what is really going on in the engine for the whole range of operations not just the few seconds you use the simple tools in the driveway. When I run a M jeep as a daily driver I use the mechanical gauges all the time. If you are showing and driving your jeep then stash the gauges in the glove box so you can still get real accurate info when you need it. Just "T" them into the engine adapters. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Oct 10, 2012 Posts: 310 Location: Toronto, Ontario, Canada
Posted: Sun May 17, 2015 5:00 pm Post subject:
While prepping mine I found a mechanical oil pressure setup (http://www.amazon.ca/OTC-5610-Transmission-Engine-Pressure/dp/B000R5G0DO) but it has been more difficult to find one for the temp.
Wes, I'm assuming any temp setup would replace the electrical temp sending unit in the head as well? _________________ Jordan
When I say mechanical gauges I mean both electric senders are replaced with mechanical devices. The oil pressure uses a tube and adapter fittings at the block and the water temp uses a capillary tube and adapter fittings at the block. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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