Which thermostat - 180F or 190F for Series 60?

[belfert]

Detroit talks about both a 180F and 190F thermostat for the Series 60, but doesn't say why to choose one over the other.

Would a 180F thermostat really keep the engine cooler?  It seems to me that the thermostat is open almost all the time once the engine warms up, so how would a 180F thermostat help cooling?

I am going to replace my thermostats and need to decide on 180F or 190F.

Brian Elfert

[gumpy]

The thermostat is what regulates the temperature in the engine. Until that temp is reached, there's very little circulation through the radiator because the thermostat is closed.

You've been sweating overheating since you bought this thing. Put a 180 in it, unless you can find a 175!

[H3Jim]

But if your 1 or 2 speed fan doesn't kick in until a higher temp, it will only run the 180 until you put a load on it, or the air temp is quite cool.

[FloridaCliff]

Brian,

Couldn't agree with Craig more.

For Grins....Put the old thermostats in a pot and slowly bring up the water temp to there rating.....

See if they open correctly or at the right temp...Might give you an idea of what was causing your previous issue....

Also test your new ones before install...Make sure they open at the specified temp and open and close smoothly.

Cliff

[belfert]

But if your 1 or 2 speed fan doesn't kick in until a higher temp, it will only run the 180 until you put a load on it, or the air temp is quite cool.

I think the fan clutch kicks in once the key is on and is only a single speed.  I will call MCI tomorrow and try to confirm for sure.  If it is dual speed, I would have to find out what temps the DDEC uses to kick the fan clutch to high.

Brian Elfert

[belfert]

The thermostat is what regulates the temperature in the engine. Until that temp is reached, there's very little circulation through the radiator because the thermostat is closed.

You've been sweating overheating since you bought this thing. Put a 180 in it, unless you can find a 175!

I've been skittish about overheating since it happened to me many times on the grades in Pennsylvania.  The engine went into shutdown mode once due to overheating and I had to pull over.  I watched the temp gauge like a hawk after that and had to slow way down on pretty much every grade to keep the temps in control.

Just yesterday or today I found the work order from the Detroit dealer in Youngstown, Ohio.  It says that radiator inlet is 40F warmer than outlet which indicates restriction in system.

Others have speculated that I merely have a partially stuck thermostat so maybe a 190F thermostat will be fine if that is the case.  Won't know until I pull the tthermostats I guess.

Brian Elfert

[H3Jim]

or perhaps the radiator needs to be rodded out.

[Stan]

To clarify the function of the thermostat, it should never be wide open unless you are exceeding the cooling capcaity of the system. It is a modulating valve that moves slightly more open or more closed as the load (and fuel demandl) changes on the engine. At idle it will be completely closed with some coolant circulating through the by-pass. The DD manual gives the ' start to open'  and  'fully open' temperatures. Under normal load, the thermostat should  be partially open maintaining the coolant in the engine  at the temperature marked on the thermostat.

The fact that buses are notorious for overheating does not mean that is the way an engine  is supposed to operate. There are many reasons for overheating, such as exceeding design criteria (too high an ambient temperature, too much load, too much horsepower, etc,) but by far, the reason is some failure in the cooling system to operate properly.

[DrivingMissLazy]

Thanks Stan for the excellent explanation of the purpose and operation of the thermostat as part of an overall cooling system. From many of the posts I have seen it appears that many people think of the thermostat as either open or closed only.
Richard

To clarify the function of the thermostat, it should never be wide open unless you are exceeding the cooling capacity of the system. It is a modulating valve that moves slightly more open or more closed as the load (and fuel demand) changes on the engine. At idle it will be completely closed with some coolant circulating through the by-pass. The DD manual gives the ' start to open'  and  'fully open' temperatures. Under normal load, the thermostat should  be partially open maintaining the coolant in the engine  at the temperature marked on the thermostat.

The fact that buses are notorious for overheating does not mean that is the way an engine  is supposed to operate. There are many reasons for overheating, such as exceeding design criteria (too high an ambient temperature, too much load, too much horsepower, etc,) but by far, the reason is some failure in the cooling system to operate properly.

[busguy01]

I have a 60 series in a 01 Eagle. I had cooling problems when I first put it in. Finally got all the issues fixed but somewhere in the process went to 170~ stats. Now the bus runs right on the stats most of the time but when my foot gets heavy on some really steep grades the extra 10~ lower starting temps does help out. Can ususlly make any grade and stay below 190 on temp. It may actually be running at a lower temp than it should be now but it is great to not have to worry about overheat. By the way - mine has a DDEC II in it and I have seen temps over 220 without a shut down.
Just my way - your mileage may vary.
JimH

[Burgermeister]

Guys,

Your missing the point if you feel installing a 175 deg Thermostat in a 180 or 190 deg system will increase heat rejection CAPACITY.

The lower thermostat only changes the "setpoint" or target temp for engine operation and may adversely affect emissions

A 175 deg. thermostat may, in fact, exacerbate a marginal system into full blown overheat.

Brian,  I'd make sure your radiator is up to snuff before you start chasing other gremlins.

Onward and Upward,

Marc Bourget