Not reaching operating temp?

[bigbeanbus]

I've had my 8.2L DD on the road as an RV for a couple days now, driven about 300 miles (1100 if you include driving it back when I first bought it). I first drove it back in the winter, had the low temp alarm blaring at me when I wasnt moving, and figured the low temps were probably my biggest problem. However, just to be sure I took the bus to a shop to have a proper coolant flush thinking if I had problems with a thermostat or anything they would uncover it
(in an effort to charge me more).

Driving now the temp gauge just barely covers the first notch right past 100, 180 is the operating temp for the engine, and I get a bit of white smoke out the tailpipe when shes first started (a problem from before the flush as well). The low temp alarm will beep for a second or two before fading away like a dying tornado siren.

I know that running at low temps isnt great for MPG and can build up deposits in the engine, but the 8.2L is very sensitive to overheating as well. How concerned should I really be, if at all/ should I try changing out the thermostat? Has anyone done that change on this engine?

[Jolly Roger bus 223]

what year model is your bus?
what type of cooling fan do you have?
i assume you have the 8.2 NA because i cant imagine a turbo diesel ever running to cool?
have you verified guage temps at the block and radiator with an infrared gun?
could be a bad guage and the alarm reads off of the guage?
need more bus info. to help you more.

[bigbeanbus]

The bus is a 1999 NA DD 8.2L. I haven't verified the temp with an IR gun yet, not sure where the best place is to get one is (have only looked at a Walmart we passed by and they of course didn't have one). Currently looking through the service manual for info on the fan but am having trouble finding out exactly what type it is. I have seen forum post elsewhere where owners say GM put too large of a radiator in these systems.

[bigbeanbus]

Originally Posted by bigbeanbus

The bus is a 1999 NA DD 8.2L. I haven't verified the temp with an IR gun yet, not sure where the best place is to get one is (have only looked at a Walmart we passed by and they of course didn't have one). Currently looking through the service manual for info on the fan but am having trouble finding out exactly what type it is. I have seen forum post elsewhere where owners say GM put too large of a radiator in these systems.

1990*** whoops it's not a 1999

[cadillackid]

shoot an IR gun at the thermostat housing in a couple different pl;aces.. (sometimes smooth or shiny durfaces throw the IR gun for a loop).


any diesel engine can run too cool.. you want them warm but not too warm.. warm means your fuel atomizes and burns completely.. better efficiency, condensation in the oil pan is evaporated, etc..



the coolant temp sensors on GMC's are a known failure point so I would definitely check with a temperature IR gun before tearing things apart..

[CHEESE_WAGON]

Originally Posted by cadillackid

shoot an IR gun at the thermostat housing in a couple different pl;aces.. (sometimes smooth or shiny durfaces throw the IR gun for a loop).

the coolant temp sensors on GMC's are a known failure point so I would definitely check with a temperature IR gun before tearing things apart..

CK is right, you don't want to throw parts and effort chasing a problem that doesn't exist.

If engine temp matches the gauge, check the thermostat. I had an engine with a thermostat that wasn't closing all the way and letting coolant bypass before it reached operating temp. Wouldn't top 155° unless I let it sit and warm itself. Some people drill holes in them to allow bypass.

[bigbeanbus]

Originally Posted by CHEESE_WAGON

CK is right, you don't want to throw parts and effort chasing a problem that doesn't exist.

If engine temp matches the gauge, check the thermostat. I had an engine with a thermostat that wasn't closing all the way and letting coolant bypass before it reached operating temp. Wouldn't top 155° unless I let it sit and warm itself. Some people drill holes in them to allow bypass.

That seems like the current plan of attack. I have a new thermostat already, but would have to grab a new gasket and deal with possibly corroded bolts, let alone draining and readding coolant. None of which is too troublesome but rather not create possible hiccups if I don't have to.

[bigbeanbus]

So after buying an IR gun, and driving a couple 100 more miles (yikes), it seems like the thermostats (two in this engine for some reason) do in fact need to be replaced. The housing around the thermostat was only reaching just over 100 degrees - which would mean my gauge is accurate.

Currently awaiting the parts to come in to the town I am currently parked in and will probably attempt to make the change tomorrow morning. Any tips for changing out thermostats? I known its relatively easy and quick, which eases some of my stress, but I just want to make sure I do not create any larger problems!

[Booyah45828]

Hopefully someone didn't remove the thermostats on you to keep it from overheating and hide a head gasket issue.

I've also never seen a low temp alarm. Typically it's a high temp/low oil pressure alarm.

[bigbeanbus]

Originally Posted by Booyah45828

Hopefully someone didn't remove the thermostats on you to keep it from overheating and hide a head gasket issue.

I've also never seen a low temp alarm. Typically it's a high temp/low oil pressure alarm.

I hope so as well; however, besides the white smoke, I don't seem to have any other symptoms of a blown head gasket. With this engine being 30 years old and having two thermostats it seems likely to me that one of them has just failed in the open position, but I guess i'll find out more tomorrow.
I don't know if it's actually a low temp alarm, when I drove it back or was winter and the alarm would kick on during idle so I figured that's what it was alerting me to.

[Booyah45828]

What was your oil pressure reading when it was at idle? If it was low, the alarm might be going off because of that.

[bigbeanbus]

Originally Posted by Booyah45828

What was your oil pressure reading when it was at idle? If it was low, the alarm might be going off because of that.

That's could have been the case considering I no longer have the problem since replacing the oil. The alarm may come on when I first start the engine but after a second or two goes off.

[CHEESE_WAGON]

Originally Posted by Booyah45828

Hopefully someone didn't remove the thermostats on you to keep it from overheating and hide a head gasket issue.

I've also never seen a low temp alarm. Typically it's a high temp/low oil pressure alarm.

This was done on a Toyota I bought a while back. Thermostat had been removed to keep the radiator from blowing out from the exhaust pressure building up in the cooling system. Turned out to have a cracked head, common to the 2200 engine it had.

However, it ran and drove with no issues and wouldn't go past operating temperature on a 95 degree day with the hood closed and the air conditioning running.

But oh boy, was that a cold son of a gun come winter...

[bigbeanbus]

Just wanted to update the thread:
This morning I pulled the housing off and pulled out the old thermostats, both of which had failed in the open position. Oddly enough it also appeared as if there was no gasket previously connecting the housing.
Engine is now heating up on its own and sitting at a comfortable 180 degrees. Thanks to everyone for their input!

[Booyah45828]

I love it when a positive outcome happens. I was worried for you that the PO removed the thermostats. Good to hear that wasn't the case.