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318LM running 130 degrees. Is this normal?

I

iflyboeing

Member
New longblock, intake and exhaust manifolds, new water pump (raw water cooled). Also new thermostat and housing. Problem is that it's running at about 130 degrees. Is it possible that the installer used a 140 deg thermostat? Why are there two different thermostats used on these engines? (140 vs 160).
 
I know that raw water cooled engines use the 160 degree thermostats and my engines top out at 150 normal. The 140 I believe is for fresh water cooling.
 
RWCooled engines use a 140 T-stat and run about 150. (FWCooled use a 160 t-stat and run about 165.)

I suspect you either have a bad t-stat (it happens) or the housing it goes in is heavily corroded. That allows water to bypass the t-stat. I use a stainless plate riveted to my smaller (and cheaper!) t-stats at a barrier with a gasket on both sides. you might have to do that as well.

Jeff

PS: 130 is way too cold. Moisture will not be burnt out of your oil, leading to sludge.
 
Tested t-stat at home. Opens and closes normally. Housing is brand new. Here's what's even more bizarre: The so-called "sweet potato" was discontinued by tech service bulletin back in the 70's. Keep in mind that this a completely new engine (long block, manifolds, et-al). The installer plugged the bypass hose. One would think that this would make the engine warm-up faster (perhaps even run warmer).

Here's what I want to know: The dual pocket pump delivers one side of it's load to to coolers and exhaust manifolds. The other side of the pump delivers it's load to the engine block. When cool, the bypass is open.....but mine is plugged. So where is the water going when the engine is cool (thermostat closed)? Is this putting back pressure on the pump?
 
I have a service bulletin (No. 210 dated Aug 1973) in my service manual which advises putting a 5/16" restrictor in the by-pass hose to increase water flow through the heat exchanger. If that helps.
Tony
 
If output is stopped, it's definately putting back pressure on the pump. Whether it harms it or not I don't know. I do know that in order for the pump to actually pump fluid, the blades must be compressed by passing over the cam. This decreases the space between each blade. When the blades pass the cam and straighten out again, the space between the blades increases there by creating a vacuum to allow fluid in. In order for the pump to continue sucking fluid, the blades must straighten out. If it can't displace the fluid, I suspect it will build enough pressure to prevent the blades from straightening and therefore creating a vacuum. Only when fluid is allowed to pass will the blades straighten out again.

I didn't get why they plugged off the bypass?
 
The original plumbing from 1968 had the bypass line feed back into the raw water intake. Chrysler called the plumbing "manifold" device that it fed back into the "sweet potato". In 1970 the sweet potato was eliminated by TSB. Chrysler suspected that feeding the bypass back into the water intake was somehow leading to overheating. As a side note, I'm not sure why recirculating the bypass water would cause overheating. When the thermostat opens, it actuates in such a way as to close the bypass. Therefore, bypass water should never be greater than 145 degrees or so.

Anyhow, the TSB directed that the bypass line was to be moved to discharge into the maniflods. My mechanic didn't do this, he merely plugged it. Yesterday, I un-plugged it and it does now flow well.
 
Curious, I have the "sweet potato" fitting and have never had the heating issue though they are 440s. Maybe that's the difference but the cooling circuit is the same.

FYI, it's not uncommon for 318s to show 120deg with proper t-stat, gauge, sender etc. You're probably fine.
 
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