+- STD (https://www.superturbodiesel.com/std)
+-- Forum: Maintenance (https://www.superturbodiesel.com/std/forumdisplay.php?fid=22)
+--- Forum: General (https://www.superturbodiesel.com/std/forumdisplay.php?fid=4)
+--- Thread: Temp sender question (/showthread.php?tid=1921)
Temp sender question - JB3 - 11-01-2010
Couple questions, I have an 84 300D and my temp gauge never gets past about 45C on the gauge. Ive got a new thermostat in there, did a coolant flush, and shot the engine with a temp gun, and it "appears" to be running at a normal operation temp.
I tested the ohms cold on the sensor in the middle of the block above the glowplugs, and got 1.07 ohms, and at hot, its like 40 ohms or such, but I had a questionable connection.
I have heard that if I take the temp lead that connects to the sender, and ground it to the block, I will peg the gauge, as a way to test if the gauge is working correctly or if there is a wiring problem, basically to isolate it to the sender if so. Can this be done and work in that way?
2nd question, the second temp sensor on the thermostat housing to run the aux pump, is that simply another sensor, or some kind of switch? Question is can I switch them, and or, can I in a emergency situation run the gauge off the front thermo housing sensor?
RE: Temp sender question - ForcedInduction - 11-01-2010
(11-01-2010, 01:03 PM)dropnosky I have heard that if I take the temp lead that connects to the sender, and ground it to the block, I will peg the gauge, as a way to test if the gauge is working correctly or if there is a wiring problem, basically to isolate it to the sender if so. Can this be done and work in that way?Yes, ground it to the block.
Quote:2nd question, the second temp sensor on the thermostat housing to run the aux pump, is that simply another sensor, or some kind of switch?That is a 40*c temperature switch that locks off the heater fan so occupants don't get blasted with cold air.
RE: Temp sender question - JB3 - 11-01-2010
(11-01-2010, 01:15 PM)ForcedInduction(11-01-2010, 01:03 PM)dropnosky I have heard that if I take the temp lead that connects to the sender, and ground it to the block, I will peg the gauge, as a way to test if the gauge is working correctly or if there is a wiring problem, basically to isolate it to the sender if so. Can this be done and work in that way?Yes, ground it to the block.
Quote:2nd question, the second temp sensor on the thermostat housing to run the aux pump, is that simply another sensor, or some kind of switch?That is a 40*c temperature switch that locks off the heater fan so occupants don't get blasted with cold air.
thanks!
EDIT- So after verifying that I had a good wire between the sensor and gauge, I grounded the sensor as described and the gauge pegged to max, pointing to the sensor as the guilty party. Removed the sensor and replaced it with a spare, which immediately showed that instead of cool, the car is actually running a tad hot at all times. I might check the water pump out now, and see if its worn, or if the little bleed line is blocked. Radiator looks ok.
RE: Temp sender question - JB3 - 11-02-2010
the car is running just above or below 100c at all times, which is too hot. Interestingly, it gets cooler when you push it, and hotter when you back off.
Running up some fairly big grades, it crept down to 95c, and on the downside, moved up to 105c.
Ive got a water pump coming anyway, but Im thinking that the water pump impeller is eroded or loose on the shaft or something, any thoughts?
RE: Temp sender question - ForcedInduction - 11-02-2010
Go to a car wash and blow out the radiator from both sides. Make sure there are no leaves or road debris packed between the rad and condenser.
RE: Temp sender question - JB3 - 11-02-2010
(11-02-2010, 07:17 PM)ForcedInduction Go to a car wash and blow out the radiator from both sides. Make sure there are no leaves or road debris packed between the rad and condenser.
I did that when i first got it, since it spent so much time in a field, but its worth a second check for sure. I don't remember blowing straight down between the condenser and radiator at least.
It will be interesting to see if it does the same thing tomorrow and hovers around 100c in the morning. Supposed to be about 20-25F tomorrow morning. Ive also got a brand new temp sender coming just in case. This one is an unknown quantity, it sort of feels like its coming up to temp too fast to be believable in the local ambient temps. When I left this morning, it was at 100c really fast and it was about 30f out.
RE: Temp sender question - JB3 - 11-21-2010
to continue with this saga-
original temp sender read cold, 50C.
Replaced it with spare temp sender out of parts engine, which immediately read hot, around 100C
Replaced it with brand new sender, which read colder, 45-50C
Replaced THAT with KNOWN good sender out of my 240, and it read hotter, 105-115C! That seems to be the most correct temp, as I verified it with a temp gun a few times, the engine is running at between 230 and 240 degrees F when its up to temp.
During all this, I discovered that the no name radiator in this car is about 1/2 inch thinner than another nissens 300D radiator I have, so I swapped them. heres a pic of them compared-
I also replaced the water pump, flushed the coolant a few times, checked that little bleed line above the water pump, pulled the entire water pump housing out and looked for blockages, same with the thermostat housing, did the same with the radiator, checked my new thermostat and will maybe replace it again, ect. maybe there is some huge blockage in the block or something?
Every single thing I do, the engine runs a little hotter every time. Theres no head gasket problem or anything (yet), and the coolant is not leaking or otherwise disappearing, it just runs REALLY hot. ie-
Now Im going back to possible faulty parts, or maybe a faulty gauge now. Any suggestions would be much appreciated, this is annoying me
RE: Temp sender question - 300D50 - 11-21-2010
Take a digital meat probe thermometor and stick it in place of the sendor, using a compression fitting and various adapters to the right thread style. Use that to verify if you have an overheat condition or not.
RE: Temp sender question - Captain America - 11-21-2010
I just use the infrared gun to check temp, those are plenty accurate.
RE: Temp sender question - JB3 - 11-21-2010
(11-21-2010, 08:59 PM)Captain America I just use the infrared gun to check temp, those are plenty accurate.
where did you check temp and what did it read? I used the gun right around the stock temp sender location. Im thinking of throwing a complete aftermarket temp gauge on to verify what temp its really running at. I just don't trust the stock setup at the moment.
RE: Temp sender question - Captain America - 11-22-2010
I always check everything; hoses, radiator, oil cooler, turbo, exhaust manifold, head, block just for curiosities sake... but as far as comparing against the temp gauge in the dash, I shoot the temp sensor itself and around the head right next to it. The gauge in my dash is dead accurate. I also shoot the thermostat housing which always reads a bit cooler.
RE: Temp sender question - ForcedInduction - 11-22-2010
(11-21-2010, 05:34 PM)dropnosky original temp sender read cold, 50C.The sensor is $12 and it lasts 20+ years, just buy one. Its one of the first things anyone should do when buying a 10+ year old car.
Replaced it with spare temp sender out of parts engine, which immediately read hot, around 100C
Replaced it with brand new sender, which read colder, 45-50C
Replaced THAT with KNOWN good sender out of my 240, and it read hotter, 105-115C! That seems to be the most correct temp, as I verified it with a temp gun a few times, the engine is running at between 230 and 240 degrees F when its up to temp.
Quote:During all this, I discovered that the no name radiator in this car is about 1/2 inch thinner than another nissens 300D radiator I have, so I swapped them.The thinner one is from a non-turbo 300D.
Quote:Now Im going back to possible faulty parts, or maybe a faulty gauge now.You verified the gauge with your thermometer.
Have you bled all the air out?
Is the water as hot as the engine? Does the radiator get hot? You may need to do a good acid flush to get rid of scale in the block. The problem with using an external thermometer is its reading the metal temperature surrounding the water.
RE: Temp sender question - Captain America - 11-22-2010
Arent we using the water to keep the metal cool? So if the metal is cool..... I mean you can't compare cylinder temp vs water or egt vs water obviously but when I shoot the temp sender with the gun it reads the same as the gauge. There isn't much difference as long as your not shooting the exhaust or something...
RE: Temp sender question - 300D50 - 11-22-2010
Cast iron, especialy thick cast iron, is a very poor thermal conductor.
The inner cylinder side could be a few hundred degrees hotter than the outside of the block, and the water temp could be something else entirely.
Hence using a sensor in the water stream instead.
As for the sender heat soaking and thermal hysteresis, that's not my real cup of tea, but someone with more thermodynamics experience can chime in.
I'd be ordering some citric acid from bulkfoods and getting some MB cooling system degreaser from Rusty.
RE: Temp sender question - JB3 - 11-22-2010
(11-22-2010, 02:07 AM)ForcedInduction The sensor is $12 and it lasts 20+ years, just buy one. Its one of the first things anyone should do when buying a 10+ year old car.
The thinner one is from a non-turbo 300D.
You verified the gauge with your thermometer.
Have you bled all the air out?
Is the water as hot as the engine? Does the radiator get hot? You may need to do a good acid flush to get rid of scale in the block. The problem with using an external thermometer is its reading the metal temperature surrounding the water.
I did order a new sender after the spare was so different from the original. The reading on that one was unusual, and extremely low.
The radiator and upper hose are all heating up like normal, and aside from the consistent high mark on the dash, everything feels correct temp to the touch in the engine bay, not way too hot, and its completely bled of air.
This is whats making me doubt the gauge and maybe the temp gun I borrowed. Im going to check the thermostat again, then attach another gauge and see if I can verify the stock temp gauge reading.
Everything appears clean in the coolant passages as well. A citrus flush is a good idea, ill put that on the list. I did several hose flushes and the water came out pretty clear.
RE: Temp sender question - ben2go - 11-23-2010
Big if,the coolant is over heating.Have you checked the fan and fan clutch?Or is that fan direct bolt on without a clutch.Is the fan shroud in place and in good condition.I'm just tossing out ideas.You are already doing everything I would do.Do you know anyone that would loan you an aftermarket gauge to compare your dash gauge to?
RE: Temp sender question - Captain America - 11-23-2010
I have not found the engine block or any other component for the matter to be such a poor conductor / trensferer of heat that you can't accuratly measure it to compare against the gauge in the dash. That's all im saying
RE: Temp sender question - JB3 - 11-24-2010
(11-23-2010, 10:59 PM)ben2go Big if,the coolant is over heating.Have you checked the fan and fan clutch?Or is that fan direct bolt on without a clutch.Is the fan shroud in place and in good condition.I'm just tossing out ideas.You are already doing everything I would do.Do you know anyone that would loan you an aftermarket gauge to compare your dash gauge to?
Im going to replace the thermostat again, maybe its faulty, later in the week. This guy over on PP had a really interesting idea, since I have the car parked directly next to the parts car, he was saying make a common ground between both vehicles, and run the temp lead from the one car over to the other and use the other gauge! I might try that, I know the 240 gauge to work properly
EDIT- While I was on the road today, I picked up a 15 dollar sunpro temp gauge as well just in case the thermostat is not the problem. Im hoping to drive the car like 700 miles in a few days, can't be running that hot! I can't believe how cheap those things are!