Thermostat

[leversole]

I have read all of the posts regarding building heat in our old trucks. People (like me) complaining that they never get above 120 degrees.

One glaring questions stands out for me, if my 160 degree thermostat is working, would it not hold the coolant IN the engine until it reaches 160 degrees? I think the issue is our old thermostats leak through, or are stuck open, which accounts for the trucks not getting to operating temperature...

I am going to pull mine out today and replace...I would think running our engines 20-40 degrees below operating temperature would result in incomplete combustion and lots of buildup on top of the piston!

Thoughts?

Leslie

[fxfymn]

You are right on; Remember the purpose of an engine is to convert heat energy to mechanical energy; the lower the operating temp the lower the efficiency. That is why Mack used shutterstats to keep the heat in (and other brands used custom made sheets of cardboard). Before you replace the thermostat try testing it. Place the thermostat in a pan of water on the stovetop using a thermometer to check the temp that it opens at.

You can also try a hand held infrared thermometer on either side of the thermostat housing before you remove it. The engine side should be hotter than the discharge side before it opens.

[leversole]

Well, here is what the thermostat looks like for those that have not seen one...put it in a pan of water and tested it. It opens at

155 degrees just like it is supposed to! This is not the problem....hmmmmm

Took me a little while to figure out how this thing is supposed to work...the hose from the bottom comes from the oil

cooler and allows that water to flow to the radiator even when the thermostat is blocking the discharge from the water manifold

Down at the the bottom is the seal that the thermostat fits in to the seal off the water from returning to the radiator, you can

see in this picture the seal is completely gone! That is why the truck would never reach opearting temperature, the water

was free flowing thru the system.

A quick trip to the Mack dealer and $40 later I have all the parts I need, gasket, O rings, water conditioner cartridge,

even new check valves for the water water conditioner.

Put it all back together, no leaks and the truck builds heat now much better than it did before...had 145 degrees pretty quick, as it

was cold today that is all of the heat that I got, but the radiator was not hot (exept for the oil cooler heat). I think it is a worthwhile quick

project which might help your engine and block! The water conditioner helps eliminate scale and rust buildup in the block...my conditioner

looked new, but the check valves were NOT working, both were seized up!

[Freightrain]

Interesting. Mine has always run at 160+ degrees pretty regularly. Lucky I guess. Mine doesn't have the oil cooler though. Is that screw-on a charged filter for coolant? Be interesting to add that to mine? I've had the coolant out of mine a couple times in the last 10 yrs, added a few new gallons, but never checked PH level. Probably should?

[fxfymn]

Did you run flush through it while you had it down? It's pretty amazing what comes out of the old iron when the system is flushed. I put a T fitting in the heater hose that has a garden hose fitting on it. Drain it, use flush, drain again, let it cool, flush it with the garden hose through the heater hose with the engine running and the radiator cap off to let the dirty coolant escape. Drain. Refill with the right amount of coolant.

[leversole]

Didnt flush it but will!

[Maddog13407]

ah 237 sooooommmmeeeday maybe my B613 will have one of those under the hood haha

[fxfymn]

Didnt flush it but will!

Just keep the dogs penned up unless there is one you don't want around anymore. They love the taste of the anti-freeze.

[96Mack]

Where is the water conditioner located ? I have a 96 RD688 and am replacing thermostat this week 

[Joey Mack]

Some don't have one.. it will be a spin-on filter in front of the thermostat housing... Front and center... jojo

[Vladislav]

On 11/23/2012 at 5:46 AM, leversole said:

Yup. Here you go. E6 or E7 mechanical has it at the same location.

[JoeH]

Should be running at 180, that's where all my Macks run, 1979-1995. Dont know what your truck setup is, if it's real light and you have no hills it'll take forever to warm up, it's meant to work hard.  A new thermostat would have been a good idea, they're not expensive.  Running cold slobbers up the valves, can make them sticky.

[JoeH]

Also make sure those 2 little pins in the side where it says "TOP" are mounted top, they're air bleeders so you don't get a pocket of air against the thermostat when you refill the system. Air won't conduct heat to open the thermostat properly on the first heat cycle.

 

Automotive thermostats frequently don't have those so I drill a pin hole in them to serve the same purpose.

Edited May 30, 2021 by JoeH

[Vladislav]

On 5/30/2021 at 2:04 PM, JoeH said:

Automotive thermostats frequently don't have those so I drill a pin hole in them to serve the same purpose.

In such case I usually put some antifreeze in the upper radiator hose to fill it up getting the upper side of thermostat sunk. Than put the hose on radiator. When you start the engine that above amount of the fluid conducts heat and supplys it to thermostat so it opens. Usually when you observe the temp gauge during the first heat cycle the temp grows up and gets a little bit higher than normal and than drops down to Ok level in half a minute.

Edited June 5, 2021 by Vladislav