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Moose · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

With the colder then usual temps down here in the past couple weeks I'm finding that it cannot hold 180 at idle past an hour. My local work is slow so I'm having to rollerskate it regionally and I found out this the hard way up in TN on night. I woke up to no heat, 12 deg ambient outside and 140 degree coolant temp. It has done it every night I've had to idle since it's been demandated and cold. It acts exactly as if the t-stat is sticking open like the older ones with the bad bridges, but this is not the case. Some history: De-mandated (fully), t-stat recently changed again (frivolously).

Now, I know with the modification already done I'm losing a large amount of heat rejection with the EGR cooler now producing zero heat while its in bypass loop but there's either something else providing cooling or I'm just not producing enough cylinder temps anymore. I'm looking for advice or history as to what everyone has possible dealt with before.

I'm thinking it's one of two things:

It looks like the coolant still flows to and from the trans oil/water exchanger along with the heater core when the t-stat is closed/bypass. I could solve this with an oil/air conversion. There is normal flow through the vent tubing even with the t-stat closed but I do not want to mess with this flow.

At idle (700) the exhaust temp is around 230F and will go as low as 200F. Raising the idle up to 1500RPM and locking the fan in I can get 360F exhaust and it will come up to temp VERY slowly. Driving the truck it will reach temp and hold it. Barely if empty and it's typical 185F coolant/215F oil temps when loaded.

smorgan87 · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

Ur idle egt's snd prty normal. As for the coolant ur either pulling A LOT of heat off thru ur heater coils or ur t stat isnt shutting off the flow. When u changed the tstat did u replace the brass press in seal and all gasket/orings? Check all mating surfaces?

Chamberpains · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

I see you stated that you lock your fan in. Just a question. But could your fan be running too much and drawing too much heatout? Why not let it go through its normal fan Cycles

Moose · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

(01-21-2018 )smorgan87 Wrote: When u changed the tstat did u replace the brass press in seal and all gasket/orings? Check all mating surfaces?

It got a new OEM t-stat, gasket and 186780 seal. I always clean with Roloc pad or appropriate for the material.

(01-21-2018 )Chamberpains Wrote: I see you stated that you lock your fan in. Just a question. But could your fan be running too much and drawing too much heatout? Why not let it go through its normal fan Cycles

This was used the day of the repair only to try and create heat while finishing up the refill process. It was mainly to say it took "this" much to force it to get up to temp. Normally, I don't lock the fan in. This truck has the two-speed viscous/air type. I've never had a need to.

trucklogger2 · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

Can you try idling up to 900 or 1000 and also cover your grill up with a winterfront or cardboard during the night? You"ll benefit with better oil pressure also.

Check your coolant for temp rating. (freezing point).

Moose · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

(01-21-2018 )trucklogger2 Wrote: Can you try idling up to 900 or 1000 and also cover your grill up with a winterfront or cardboard during the night? You"ll benefit with better oil pressure also.

Check your coolant for temp rating. (freezing point).

I was trying not to have to resort to a winterfront or high idle. If I have to spend that kind of money I'll get a Webasto and just not run the motor. I haven't looked at the fuel consumption numbers but it has to still be less than idling it that high.

Coolant was reused & tested for freeze, SCA & Ph when we did the t-stat. It only has around 50k on it.

I was just throwing the problem out there in hopes that others have had similar issues and it was a known fix.

trucklogger2 · 01-21-2018, **(Subject: ISX CM2350 trouble maintaining temp )**

(01-21-2018 )Moose Wrote:
(01-21-2018 )trucklogger2 Wrote: Can you try idling up to 900 or 1000 and also cover your grill up with a winterfront or cardboard during the night? You"ll benefit with better oil pressure also.

Check your coolant for temp rating. (freezing point).

I was trying not to have to resort to a winterfront or high idle. If I have to spend that kind of money I'll get a Webasto and just not run the motor. I haven't looked at the fuel consumption numbers but it has to still be less than idling it that high.

Coolant was reused & tested for freeze, SCA & Ph when we did the t-stat. It only has around 50k on it.

I was just throwing the problem out there in hopes that others have had similar issues and it was a known fix.

If you are looking for a quick fix go get a vasectomy. In the meantime check your coolant hoses from your engine to your water valve. Hot or just warm? If hot your problem is water valve or dump door or in your cab. Are the sleeper hoses the same? Must be. You will have to look at your thermostat again otherwise.
Idle at 700 is stupid