View Full Version : 6.5L temperature issues
I recently bout a 1994 Chevrolet 3500 6.5L diesel. For some reason my “low coolant” light will come on. And my temp gauge stays about a 1/4 way. An will rise at times to full hot but with in two seconds it will go back down to 1/4 way. Heat blows great. My second issue is I am having white smoke coming out of my dipstick while the engine is running. It will only blow white smoke at startup from the exhaust then nothing. Runs great. Has 114k miles on it. I’m not big on diesel motors but can definitely fix anything with some directions or tips.
If you are adding coolant and in a short the light is back on you likely have an internal coolant leak.
Take a look at the oil and see if it's gray and sloppy looking.
If you are adding coolant and in a short the light is back on you likely have an internal coolant leak.
Take a look at the oil and see if it's gray and sloppy looking.
Oil looks good, I just filled the coolant. Took only about 1/2 a gallon so it seems to be holding. Haven’t seen any leaks it all. Even when it is parked over night.
Start the rig and allow it to warm up with the hood up.
Observe the top radiator hose and see if it gets HARD while the engine is warming up.
I it gets hard it means there is a head gasket/combustion leak.
A small leak will go by somewhat unnoticed for a time.
The temp should rise steadily and level off at about 190/210 and not pin the gauge and then fall.
Could be a goofy T stat too.
See what shakes out.
I will try that as soon as I get home to see if the hose gets hard. I was thinking maybe a sticky thermostat as well, I am going to buy one just too try out. Other than that it may be a issue with the white smoke coming from my dipstick. While the truck is running.
trbankii
02-23-2019, 09:21
I'm dealing with a similar issue with my '94 Yukon - low coolant light comes on with coolant at normal levels and no overheating issues. If I mess with the wires going to the sensor, it usually goes off but comes back on again in a day or two.
I need to pull the recovery tank to see if I can get better access to the sensor and wires to see what is going on.
Alright, testing the radiator hose today.
Hose stayed soft after starting engine and idling.
Temp gauge gradually rose to around 190 stayed for a few minutes.
Then rose to around 230. Then fell back to around 180-190.
Has me puzzled. No leaks. Not overheating.
I'm dealing with a similar issue with my '94 Yukon - low coolant light comes on with coolant at normal levels and no overheating issues. If I mess with the wires going to the sensor, it usually goes off but comes back on again in a day or two.
I need to pull the recovery tank to see if I can get better access to the sensor and wires to see what is going on.
It is weird. My low coolant light will come on after the gauge goes all the way to hot, then when it drops back to normal the light will pop on.
I just bought a new thermostat gonna throw it in here in few minutes see if that will fix the issue.
Also, going to do an oil change. The smoke coming from the dipstick worries me quite a bit.
When the eng. is at full operating temp. and you've been driving it, do you hear any bubbling from the coolant reservoir after you shut it down?
DmaxMaverick
02-23-2019, 16:59
It's easy to find out what's huffing out of your crankcase. Stick a thick/smooth piece of steel in the freezer for an hour (bar stock works well, but it can be just about anything, just needs to stay very cold for a while). Leave in the dipstick. Remove the oil filler cap. Start engine. Hold the chilled piece in the vapor stream and see what condenses onto it. Beware of the spinning fan. The feel and odor can also be very telling. Soot/smoke, oil, and coolant are unique.
What Maverick said ;)
Another thought came to mind....has the engine been "BURPED"
With the engine off...open the air bleeder valve on top of the T stat housing and allow any air to escape and add coolant to the coolant tank until coolant flows out the bleeder valve.
These engines have to be bled out due to the way the coolant fill tank is situated and plumbed into the system.
The coolant tank feeds into the lower radiator hose and the radiator and upper part of the system can have an air bubble.
Once the stat opens the coolant will flow, but the bubble is still in there and needs to be bled out.
See what shakes...
My low coolant light will come on after the gauge goes all the way to hot, then when it drops back to normal the light will pop on.
Did you mean to say "pop off"? That sort of behavior sounds a lot like there's a huge air bubble in the cooling system that's interfering with normal circulation of coolant. How the air got there is the big concern...
(Yeah, what she said...) ;)
Did you mean to say "pop off"? That sort of behavior sounds a lot like there's a huge air bubble in the cooling system that's interfering with normal circulation of coolant. How the air got there is the big concern...
(Yeah, what she said...) ;)
I have figured out the temp issue. I replaced the T stay and the temp stays where it needs to be. However, the light for “low coolant” light will still come and go.
As for the smoke in the dipstick, had a friend of mine check it out. Not really sure what valve he said it was called. But, it goes into the motor little white piece. He pulled hose out of the part by turbo and put covered the hole. The smoke went away from the dipstick. Opened it back up an smoke came back. He said either that valve is probably clogged or something. Or a ring is out. However, I’m not certain still. I haven’t pulled the valve to check yet will be doing that tomorrow.
Also, if any of y’all have any tips on how to get alittle more power out of this rig would be appreciated.
The "GIZMO" by the turbo is the CDR VALVE
Crankcase depression valve.
This valve allows the intake airflow into the turbo to create a small low pressure in the crankcase.
The valve regulates this low pressure to a specific level to allow blowby from combustion to be removed.
Does the engine still have the factory air cleaner and plumbing connected ???
Seeing a whispy trail of vapor out the dipstick or the oil fill cap if removed (at engine idle) is not that uncommon on a high mile engine.
To get more power....
4 inch free flowing exhaust.
A better turbo
A power chip or ECM flash (96 and later needs the ECM FLASHED)
Our member John Kennedy can help with the power mods.
The "GIZMO" by the turbo is the CDR VALVE
Crankcase depression valve.
This valve allows the intake airflow into the turbo to create a small low pressure in the crankcase.
The valve regulates this low pressure to a specific level to allow blowby from combustion to be removed.
Does the engine still have the factory air cleaner and plumbing connected ???
Seeing a whispy trail of vapor out the dipstick or the oil fill cap if removed (at engine idle) is not that uncommon on a high mile engine.
To get more power....
4 inch free flowing exhaust.
A better turbo
A power chip or ECM flash (96 and later needs the ECM FLASHED)
Our member John Kennedy can help with the power mods.
Yes that is the one! And I’m going to guess that this truck does have all factory everything. It has 114k miles on her. Was a 1 owner. Old man I bought it off of.
I’m new too diesels as you can tell, so some of my questions about what things are called may sound dumb. Haha. I’m going to check the air filters and things today, I am also going to do the complete oil change.
Well, did the oil change today, as well as burped the coolant.
Crazy that the piece there going into the motor by the turbo is just a plastic piece of pvc. Is it supposed to be like that? Cause someone said you should be able to shake it and hear a piece rattle or something.
Oil was blacker than black, got it all changed out with a pretty good new filter.
Now, just gonna do the small other little things to try to get this engine tip top. Would definitely like to get some more power, as I pull a lot of horse trailers and really what I got this truck for.
Does anyone know the bolt size for the front driveshaft? I have to install it yet. Have the shaft just not the bolts.
I attached pictures of the pvc valve. If someone can tell me why it is just a plastic piece of pvc. Just doesn’t seem right to me.
It presses down into the motor right by turbo, then has a hose connected to it that goes to in front of the turbo before the air filter where the hose is pressed into. I will get another picture as to where exactly it goes if someone doesn’t know what I’m trying to explain.
First two pictures are of where the pvc piece goes and where the hose leads too.
Last 3 pictures are of a line I discovered that has a bolt in it.
Any ideas of if it is needed or what? I believe after tracking it down it goes into the plug in the back of the pictures.
The last photo shows a thin plastic line that probably went to a boost gauge at one time. There should be a Crankcase Depression Regulator (CDR) about the size of a tuna fish can with a fitting stuck into one of the valve covers A hose from there goes to the rubber connector between the air filter box and the turbo inlet. Air rushing through there creates a vacuum. The CDR regulates how much of that vacuum is applied to the valve cover. A slight negative pressure in the crankcase evacuates any blowby and helps prevent oil leaks.
Here is an exploded view of the CDR. (https://www.thedieselpageforums.com/tdpforum/showpost.php?p=308600&postcount=20)
https://www.thedieselpageforums.com/photopost/data/500/CDR-diaphragm.jpg
The last photo shows a thin plastic line that probably went to a boost gauge at one time. There should be a Crankcase Depression Regulator (CDR) about the size of a tuna fish can with a fitting stuck into one of the valve covers A hose from there goes to the rubber connector between the air filter box and the turbo inlet. Air rushing through there creates a vacuum. The CDR regulates how much of that vacuum is applied to the valve cover. A slight negative pressure in the crankcase evacuates any blowby and helps prevent oil leaks.
Here is an exploded view of the CDR. (https://www.thedieselpageforums.com/tdpforum/showpost.php?p=308600&postcount=20)
https://www.thedieselpageforums.com/photopost/data/500/CDR-diaphragm.jpg
Yeah the thin plastic line is too a boost gauge. The last photo shows that plug with the blue connector there. That’s where the line with the bolt in it goes too.
And I figured it was supposed to be something else other than a plastic pvc pipe coming out of there. Definitely looked off. I wonder once I go buy a CDR it will make my smoke from the dipstick go away.
The truck does miss here and there usually only after it’s been warmed up for a few minutes, or on take off up the road. But, works itself out of it.
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