M38 Thermostat

RonD2 · Post by **RonD2** » Thu Feb 21, 2019 9:51 pm

After much research, I don't see a down-side to drilling the 1/8-inch bypass hole in the flange of the thermostat that's been suggested in several posts going back years in this and other forums. The range of opinion as expected --- from --- it won't harm anything --- to it's not necessary --- to it improves the overall L134 cooling system. Some even say two holes is better than one.

Nothing in any TM that I can find says to do it. I'm thinking if it's such a good thing then why isn't it in the TM? Why can't I buy a thermostat with the hole already in it? Which makes me think it's all just another urban (jeep) legend.......or maybe it's one of those things real mechanics learned in ancient times from mechanics that taught them and nobody bothered to put it in the manual?

I've got a M38 head with the by-pass hose and have a 160-degree thermostat as called for in the M38 TM. Summers are hot and humid in South Carolina. Winter is better

.

With your help, I'm just trying to find some ground truth, and another gold nugget for my thimble of knowledge. Unless you kind gentlemen tell me that little hole can cause bad things --- then I'm inclined to get the drill out (and note the unauthorized modification in my log book

). Thanks!

Post by **wesk** » Thu Feb 21, 2019 11:34 pm

You are chasing an unnecessary modification. Your bypass hose already has that one or two 1/8" hole crap taken care of. In the future try posting links to the BS stories you are reading so we can all enjoy a fantasy trip!

RonD2 · Post by **RonD2** » Fri Feb 22, 2019 9:03 am

Search "thermostat" ---- here's one of many hits for your reading pleasure:

http://willysmjeeps.com/v2/modules.php? ... thermostat

Still no down side

Post by **wesk** » Fri Feb 22, 2019 10:37 am

Still no down side

Actually that's how a non mechanic or driver would feel.

There are a few downsides:
1 - you are playing for no good reason with the operational integrity of an important part.

2 - Your putzing with this important part damages it's structural integrity.

3 - Your jeep will not have a stock M38 thermostat.

THE UPSIDE: Nothing gained!

RonD2 · Post by **RonD2** » Fri Feb 22, 2019 6:41 pm

Ok Wes, thanks. I didn't realize this was such a big deal.

By the by, I don't have a stock M38 thermostat now. I believe the stock thermostat is a "bellows" type that isn't made any more?

I have the modern "pellet" type (I think its called) --- available from most any auto parts store. Wish I could find one Made in U.S.A.