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Joe's '91 405 Mi16...


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In that case it's an easy fix, try changing the oil temp sensor, its the one next to the oil drain plug on the oil pan. They are cheap, if that doesn't fix it, you can add resistors to the wire from the sensor to add or subtract resistance, with that lower the gauge reading.

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Hey guys, was able to get the car up on my lift today and figure some things out. For starters, the connection to my oil temperature sensor was fine, no corrosion, just a little bit of oil, so I disconnected and cleaned everything, and put it back together snug. Took it for a drive this evening and all the same symptoms.

Another thing I noticed is that the oil level gauge is quite erratic too. When you turn the ignition on, it gives you a reading on the gauge, if I turn it off and then turn it back on again I get a completely different reading, and so on and so forth. So it just seems like the sensor is bad at this point.

I spoke to Brian Holm, but he doesn't have any in stock and cannot get one for at least six weeks. Anyone else know where I can get a sensor in the meantime? I checked all the regular places I would normally check, but no luck…

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I can’t see it taking much effort to ensure they work properly, so why not see if it can be made accurate?

The resistance of the sensor should be easy to test, usually the higher the resistance the higher the temperature indication, but making sure it’s within spec is the first think I’d do since issue could be gauge side.  If it’s a single wire connection you may want to check and clean engine grounds as well to ensure pan is nicely grounded.

There’s a Vendor section on the site as well, either Madhu or Rob in Texas would be good to check with.

Rabin

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12 hours ago, Mike T said:

Those oil level gauges were next to useless when the car was nearly new so I'd simply ignore it and enjoy the temp. gauge.

I agree, I'm not too concerned about the oil level gauge, that's simple enough to check on my own...

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1 hour ago, Bean said:

I can’t see it taking much effort to ensure they work properly, so why not see if it can be made accurate?

The resistance of the sensor should be easy to test, usually the higher the resistance the higher the temperature indication, but making sure it’s within spec is the first think I’d do since issue could be gauge side.  If it’s a single wire connection you may want to check and clean engine grounds as well to ensure pan is nicely grounded.

There’s a Vendor section on the site as well, either Madhu or Rob in Texas would be good to check with.

Rabin

Fair point, I already cleaned everything at the sensor, might have to go up and check it at the block.

Also I'm not sure what the resistance should even be on the sensor, anyone have that information?

Lastly, electrical is not my specialty. I have a multimeter but can't even remember the last time I used it. Also not sure which setting I should be checking it on. Any help with these matters would be most appreciative…

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Rob Courter is Javel Garage in the vender section on the home page.  
 

To check the resistance you set the multimeter to ohms and check the reading from where the wire connects to the body of the sensor or it’s ground.  If you Google the sensor you often will find the specs for it as well.

FSM should have that info, but I don’t think I have any 405 manuals.

Rabin

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When my 405 was nearly new it gave wonky oil level readings (I'm talking about 30,000 km under warranty) and I was told at the dealer that the sensors/gauges were crappy and not accurate at all.  As the car aged it got worse but it's not worth wasting any further thought about it IMO.

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If my experience with the local Peugeot dealer in the late 80’s was anything to go by, they were ridiculously undertrained Dodge/Plymouth/Chrysler dealership dudes that had little to no interest in these cars.  
 

In my experience that’s usually the response one gets when they have no idea how to fix it and really just want you to concede and accept the flaw.  :)

Temp and level should be dead simple to suss out, but I’m likely too OCD to not let that bug me. 
 

Rabin

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Thanks for the information guys, I obviously have some more stuff to figure out here...

I guess I never realized that the oil temperature sensor acted alone, and the oil level sensor is a different one altogether. I never considered that the gauge could be an issue, but now it seems like that is another potential here… 

Still looking for the specs on the oil temperature sensor, but I should be able to find it. I'll also check the connections at the block for both sensors and go from there...

Will update soon, and thanks again, you guys are the best...

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  • 1 month later...

Gentlemen, long time, no update...

I've been enjoying trouble free driving in the Mi16 for the last couple months, as I waited for my oil temperature sensor to arrive, and it finally did the other day, so after a few days of fiddling around in the garage, it is now installed.

However, my issue is still there with the higher readings. My first clue that this wasn't going to fix my issue was when it arrived, I tested the ohms on it compared to my original one. Sadly, they were reading almost the same. I kind of figured that it was unlikely to cause any changes once the new one was installed, and of course that was the case. Was worth a shot for the low price/effort, plus my oil was due to be changed anyways...

Seems the issue now may lie in the gauge itself (good call, Bean), since as I noted, the oil level gauge too gives seemingly incorrect/inconsistent readings. I now have to decide how far I want to go with this issue...

Since I've been able to verify oil temperature with my infrared gauge (getting around 175-185 when I shoot the bottom of the pan), I think it is safe to assume my gauge is regularly reading about 50 degrees too high. I hate looking at it knowing this, but at least I know for sure now...

Options at this point now are to pull the cluster and then ???

I already briefed my mechanic on this one, he's not sure yet if he wants to start pulling the cluster apart. Can't say I blame him, as I don't want to either. I could buy a used cluster from Brian Holm I guess, and then try to match the odometer. Or try to find the gauge itself if possible and swap into my cluster? But struggling a bit with the decision of whether it's worth it or not...

Thoughts?

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I’d calibrate the sensor readings with the temps using a potentiometer to add resistance to circuit in series, or run it in parallel to lower the resistance  to the point where it reads the temp the same as the gun.  
 

Sensor is fixed/not adjustible, and you really have no idea if the gauge cluster can be adjusted, but since it all works, “calibration” is all it needs to work properly.  I’d wager once the proper resistance is found, that will bring the gauge range into proper spec.

Rabin

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First try to check the wiring, sadly I don't have any 405 wiring diagram but looking at the 309 diagram you may have many things that can go wrong between the sensor and the cluster:

1655065133_Recepteurscombin309.thumb.png.769062a996c2aea12b8ca7817b6da7b5.png

Anyway removing the cluster doesn't look too hard: http://xrms.free.fr/phpwebgallery/category.php?cat=12&start=0

Sure you need to take the top of the dashboard off but after that you got plenty of space. For having done the exact same fix than this guy on a 309 I can tell you that it's not as fun when you need to put back the cluster.

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Guys, thanks for the responses. I like what you both are thinking, and will continue to try and figure out this issue.

Does ANYONE know the specs of the oil temp. sensor? I have been unable to find them. That would be a great start, as my mechanic has some ideas as well...

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  • 2 months later...

Gentlemen, long time, no updates...

Been slammed this summer (which is the usual routine for me), and the Mi16 has regrettably gotten very little attention these past couple months (my work is busiest in the summer), however the gentleman I bought my car from did bring me a spare gauge cluster, once time allows I will pull mine out and see if it is even the same cluster as what I have. I believe there are 2 manufacturers. If they are the same, I'll swap out gauges and see what happens. Not much more I can go on at this point, since the new oil temp. sensor didn't change anything. Will update at that time...

Hope you all are doing well.

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Always nice to see updates even if they're just to say hi...  :)

You might want to check the sensor values via the wiring to the cluster when you have it out.  If you see the same / close sensor values as you do at the sensor then you can rule the wiring out at least.

Rabin

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  • 4 weeks later...

Gentlemen, another update...

Took the car out for a ride the other day and noticed the cooling fans were taking WAY longer than normal to come on - close to 220, and even then only the low speed function (I think) seemed to come on. No sooner than when the car got that hot, I was merging onto the highway, and it quickly got back down to 175-180, which is pretty normal from what I've seen with this car.

The car has 3 coolant temp. sensors that I'm aware of, the 1-pin connector for the gauge, the one nearby/below for the ECU, and one one that goes vertical up into the water jacket, which I think is for the fans? This sound correct? A friend and I did some diagnosing, and after jumping with a paper clip the one that we suspected was for the fans, the cooling fans instantly went on the high mode. 

Our takeways - not a wiring or relay issue, so that fan sensor most likely needs replacing?

Thoughts?

 

IMG_7616 (2).jpg

IMG_7617 (2).jpg

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Small update, after speaking to Brian Holm, it seems there are 5 total sensors/switches related to coolant temperature. The 3 clustered near the thermostat / water jacket are the one for the temperature gauge (1 wire), one for the signal to the ECU, and one for the fans (we think). Then there are 2 others, a low coolant warning (suspected to be in the radiator), and an overheat light sensor (not exactly sure where this one is located).

I ordered the sensor for the fans, as well as one for the temperature gauge (just to be sure everything is accurate/linked). Once it arrives I'll install and update accordingly.

 

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