M38 Boilover question

Scott21 · Post by **Scott21** » Sat Feb 20, 2010 8:57 am

I get boilover in my 38 when I put a thermostat in. I have just recored the radiator, rebuilt the water pump. When the thermostat is out the flow is great. I am thinking that I keep putting the MODERN thermostat in wrong. How should the thermostst sit. Spring up or spring down??

Scott

Post by **wesk** » Sat Feb 20, 2010 9:34 am

Sensor bulb/tube goes down. Don't forget the spacer.

Scott21 · Post by **Scott21** » Sat Feb 20, 2010 1:48 pm

Wes,

I had it on the wrong side of the retainer. And backwards, too.

thanks

Scott

Keith · Post by **Keith** » Mon Feb 22, 2010 8:19 am

Is the thermostat a must have or is it optional?

Keith

cmpman · Post by **cmpman** » Mon Feb 22, 2010 8:53 am

Thermostats are a must have, especially in colder climates. If the engine is not to operating temp, it will develop sludge. We used to see it as a milky white foam in the oil on the dipsticks, especially during our harsh winters. Sludge will significantly lessen the lifespan of an engine. Quite frankly, I never found the Willys engine would last much more than 35,000 miles before the wear on them would require overhaul or replacement. One certainly wouldn't want to shorten that lifespan by saving a couple bucks on a cheap (or no) thermostat.

Regarding the problems with modern day thermostats, I definitely found that some house brands of thermostat do not compare to the quality of an auto manufacturers thermostat. Some house brand thermostats with a temp rating of 180 does not open until it is near 240 degrees. With the low radiator pressure of the old jeeps, this temp results in boiling over before the thermostat opens and maintains the 180 temp.I prefer the Ford Motorcraft brand myself, and have never had a problem with one of those in a Willys.

Post by **wesk** » Mon Feb 22, 2010 11:17 am

Engines in southern climates also need to use the thermostat. Otherwise they too will never reach a normal operating temp range. This normal temp operating range not insures we burn of the moisture in our engine's oil but also contributes to less cylinder wear and better fuel economy.

More often than not the owner leaves a thermostat out due to overheating problems as a cheap band aid to a problem that has nothing to do with the thermostat such as clogged radiator or block passageways, bad pressure cap, bad water pump and timing advanced too far.

Anytime you feel the need to change a thermostat you should suspend both the old and new thermostats in a pan of water (so they don't touch the sides or bottom of the pan) them suspend a thermometer in the water and heat the water. Water boils at 212 F so monitor and record the temps that each thermostat starts to open at, is fully open at and then when both are fully open remove the heat and record what temps they start to close at and then are fully closed at. Compare those numbers to the spec sheet.

Scott21 · Post by **Scott21** » Tue Feb 23, 2010 6:17 pm

Wes,

Had no thermostst when I brought my 38 home. Come to think about it the radiator was so sealed up I had no flow. After the recore and cleaning out the block everything is great with a super flow with the thermostat out. Who sells the NOS style thermostst? Oe which new style should I use. How should it sit on the head? I had it in FUBAR.

Scott

Post by **wesk** » Wed Feb 24, 2010 12:54 am

http://www.willysoverland.com/index.php ... 345/early/

http://www.kaiserwillys.com/category/willys_thermostats

http://www.walcks4wd.com/Product/Retain ... d-4-C/2633

http://www.willys-jeep-parts.com/produc ... cts_id=654

You hold the thermostat housing upside down. Insert the thermostat with it's temp sensing pellet facing you then slip the retainer support in narrow end first. Now lay the gasket on the head and flip the thermostat housing right side up on the head and bolt it down.