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Old 01-25-2021, 08:19 PM   #1
volvowagoon
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Default Over cooling?


1989 245 DL LH2.4 with temp faker bypass

I was in my cluster for the billionth time. This time it was replace the odometer motor. While it finally fixed my issue, a new one immediately arose. This time it was the temp display you see above. Coincidence? I think not.

My first reaction was to replace the thermostat. In the early summer I was having a problem with overheating at stoplights or heavy traffic, but it suddenly just went away without any sort of repair. When I removed the old thermostat, it was pretty apparent with manual manipulation that it could get stuck open or closed. The new one was nice and smooth. I thought for sure I had it figured out.

Nope. The needle still won't move above the 7:00 mark. Now I don't know what else to question besides the gauge.

If I'm looking at this right, the problem can only be in the red. If that voltage regulator was bent or something it would hurt my fuel gauge too. Right? I filled up today, so I know it works through at least the top 75% of it's sweep. Should I unplug the temp sensor and see If my meter will find a 10V drop between the wire and sensor terminal? Thanks in advance.
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Old 01-25-2021, 09:21 PM   #2
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Quite interesting. I cant help, but staying tuned. I have a new/ old 850 with a stuck thermostat, I just discovered. Easy fix later. yeah, troubleshoot the input signal. Or try a second gauge cluster. Sort out the issue. Best advice I ever had at engineering. Split the system in half, find which side has the problem. Good luck, bricker!

Thermostat hit the wrong hole. I love it. Hahahahaha
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Old 01-25-2021, 10:00 PM   #3
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Does you fuel gauge work as expected?

If not, look at 'M'.
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Old 01-25-2021, 10:12 PM   #4
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Quote:
Originally Posted by TestPoint View Post
Does you fuel gauge work as expected?

If not, look at 'M'.
Yep. I filled up from red today, and the needle went all the way to full.
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Old 01-25-2021, 10:13 PM   #5
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I use the 82C thermostat and on a 30F day like today that's where the needle runs. Should run a bit higher if you use the 88C thermostat.

I've had the whole stamped top of those thermostats come apart. The Vernet brand versions are nice. Sometimes the wahler type like that is all you can find and they do work ok. It's just you know it's going to fail sooner.
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Old 01-25-2021, 10:22 PM   #6
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Quote:
Originally Posted by dl242gt View Post
I use the 82C thermostat and on a 30F day like today that's where the needle runs. Should run a bit higher if you use the 88C thermostat.

I've had the whole stamped top of those thermostats come apart. The Vernet brand versions are nice. Sometimes the wahler type like that is all you can find and they do work ok. It's just you know it's going to fail sooner.
Good to know! This one is an 87°. I just find it odd that I never noticed this kind of behavior before. Then again, I might have still had the temp faker last winter.
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Old 04-12-2021, 12:16 PM   #7
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So this issue is still happening. My theory for a while was that the rich running condition caused by exhaust leaks was actually cooling the engine down too much. Now those leaks are closed up, the engine runs a lot better, and the "overcooling" issue remains. When ambient temps are around 80, the gauge displays 9:00, but at 60s or lower it doesn't get above 8:00. Strange.

I never fiddled with the gauge wire either, so I'm not necessarily looking for more ideas. I'm just letting everyone know that I'm lazy and haven't done anything to resolve this issue. Maybe the ambient temps are causing shrinkage and expansion of my wire kinda like my odometer motor? Doubt it, but who knows!
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Old 04-12-2021, 12:19 PM   #8
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perhaps measrure temp of thermostat housing.
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Old 04-12-2021, 12:57 PM   #9
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Have you ever thought about the possibility that the gauge itself is the problem? I don't have a service manual for the 240; but, I expect that there should be a calibration test that you can perform by disconnecting the sensor and applying a resistance between the sensor wire and chassis ground. Given that the gauge has no numbers, the test specs usually provide two test points

R1 - bottom of markings
R2 - start of red

It is also possible that your sensor has gone out of calibration.
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Old 04-12-2021, 01:22 PM   #10
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Testing procedure per the greenbook.

Quote:
Testing temperature gauge
lf the temperature gauge is faulty, the faulty component
(sensor, indicating instrument or voltage regulator)
must first be traced and then the fault
remedied. ln order to trace the faulty component,
two or possibly three resistors are required, one or
two at 40 ohms and one at 282 ohms.

Trouble shoot as follows:
First disconnect the electric cable from the temperature
sensor and then connect up the 282 ohm
resistor between cable and ground.
With the ignition switched on, the pointer on the
indicating instrument should be at the beginning of
the green field (=122°F). Instead of the 282 ohm
resistor, then connect the 40 ohm resistor. The
pointer on the indicating instrument should be at the
beginning of the red field (2480F). With correct
indicating instrument function, the sensor is defective
and should be replaced
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Old 04-12-2021, 01:32 PM   #11
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One benefit of having owned Turbobricks for decades is having a bunch of spare parts readily available; were I in the OP's shoes I'd remove the cluster and swap in a replacement fuel gauge to rule out that possibility.

Maybe you can source a spare at a JY?
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Old 04-12-2021, 02:55 PM   #12
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Quote:
Originally Posted by apachechef View Post
perhaps measrure temp of thermostat housing.
Do you know about how hot it should be? I think I mentioned in my build thread that it was only up to 145F while being measured with an infrared gun.
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Old 04-12-2021, 03:13 PM   #13
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Quote:
Originally Posted by volvowagoon View Post
Do you know about how hot it should be? I think I mentioned in my build thread that it was only up to 145F while being measured with an infrared gun.
Theoretically it should match the thermostat set temperature, or at least be fairly close.

IR thermometers aren't necessarily super accurate especially on shiny surfaces.

Could try measuring temp of the radiator hoses. Could also measure other points for comparison, or a known temp (like a pot of boiling water, or the housing of a home thermometer) for a bit of sanity check.
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Old 04-12-2021, 05:17 PM   #14
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At idle, particularly when the air temp is cool the temperature of the coolant in the engine outlet hose fluctuates about 6 Deg C (give or take) because the thermostat tends to be a bit of a bang bang controller - goes open, goes closed, goes open ..... At higher engine loads it tends to get a little steadier.

So, at idle you will typically measure a fluctuating temperature. You are also measuring the outside of the housing which runs at a slightly lower temperature than the actual coolant temperature. That said, if the engine was as hot as it was going to get, 145 F is only 62 C and even allowing for the typical temperature fluctuations and temperature gradient through the housing that seems too low. Either your IR thermometer is out to lunch or your thermostat is out to lunch. For more accurate temperature measurement I prefer a thermocouple which I can slip under the hose where it clamps to the housing and can be positioned right in the coolant flow.

Last edited by 142 guy; 04-13-2021 at 01:06 AM..
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Old 04-12-2021, 07:54 PM   #15
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The TempFaker has its place
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Old 04-13-2021, 07:56 AM   #16
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Thanks all. I have pretty strong trust in my IR gun. It was really accurate when I put it up against a calibrated standard, but I only checked up to 40C. When I say that I'm pointing at the T-stat housing, I actually mean at the upper hose right where the housing exits. Either way, 145F sounds like it's too low. I'm on my second brand new thermostat, which has been in and out a couple times to check for wellness. I haven't tried putting it in a pot of hot water to see if its operation is smooth or anything like that, but it would be a bit odd to have two bad brand new thermostats.

I don't know. Weird stuff. Maybe it's worth seeing what it will do with the fan removed while cruising the neighborhood. It does only seem to hit operating temp if we are in stop/go traffic (rare). Once you open up the throttle though that temp shoots down to nothing in a matter of a minute or two. FWIW that fan really feels like it's giving it all she's got even at cold idle.

Last edited by volvowagoon; 04-13-2021 at 08:01 AM..
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Old 04-13-2021, 12:28 PM   #17
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Even though you've tried two, it really seems from all the symptoms like it's just a thermostat opening too early.

Are they both the same brand? Maybe they just made a bad batch.
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Old 04-13-2021, 12:52 PM   #18
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Sounds like a bad fan clutch
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Old 04-14-2021, 04:11 AM   #19
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Quote:
Originally Posted by 240240 View Post
sounds like a bad fan clutch
Interesting ..or part of several weird junk going on ?
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Old 04-14-2021, 08:51 AM   #20
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Quote:
Originally Posted by Khrrck View Post
Even though you've tried two, it really seems from all the symptoms like it's just a thermostat opening too early.

Are they both the same brand? Maybe they just made a bad batch.
I tried buying two different brands only to find out that both were made by Wahler. Is there a different one I should try?
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Old 04-14-2021, 09:18 AM   #21
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Remove the lead and test the resistance of the sensor connector to ground .

Approximations but:

212 degrees 185 ohms
160 degrees 450 ohms
100 degrees 1600 ohms

That will eliminate, or not, the sensor.
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Old 04-15-2021, 12:20 AM   #22
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Quote:
Originally Posted by volvowagoon View Post
I tried buying two different brands only to find out that both were made by Wahler. Is there a different one I should try?
Wahler usually pretty good quality. Better than stant, gates, etc. Having said that nothing is fail proof, as evidenced by your old one. I’d test the new one(s) you have in a pot of water with a thermometer. Heat from cold, and observe what temp it starts to open and when fully open.

With your IR thermometer check the rear of the head when hot. 185-195 is a reasonable number there.
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Old 04-20-2021, 04:45 PM   #23
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The other brand of thermostat is Vernet. Both the Vernet and Wahler are supplied by other brands like Stant for example. They just rebox the Wahler or Vernet ones. Beck Arnley supplies reboxed oem stuff but I don't know whether it's the Wahler or Vernet version. The only bad part about the Wahler ones is that they can fly apart when the rivets fail.

BTW using an 82C thermostat my car runs with the gauge at that location in the winter and just a bit higher in the summer.

Last edited by dl242gt; 04-20-2021 at 04:46 PM.. Reason: add comment
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