coolant temp sensor issues - CTS

[Mikem635csi]

Hello all,

Wanted to confirm something:

I still get hesitation during acceleration although all vacuum tubes have been changed and all kinds of other tune up done...(too much to list).

I remember reading something about teh CTS being a possible culprit in hesitation problems. My cts is brittle and after driving the car for sometime, I notice tiny air bubbles coming out of cts connection to the expansion tank. Obviously something is going on there and air/collant is escaping when engine is hot.
Q- can anyone confirm the CTS contributing to hesitation/loss of power issues?
Q- my dash temp guage seems not to work as well. Is this related to the potential CTS issue?

thanks in advance..

[carsnplanes]

Hello all,

Wanted to confirm something:

I still get hesitation during acceleration although all vacuum tubes have been changed and all kinds of other tune up done...(too much to list).

I remember reading something about teh CTS being a possible culprit in hesitation problems. My cts is brittle and after driving the car for sometime, I notice tiny air bubbles coming out of cts connection to the expansion tank. Obviously something is going on there and air/collant is escaping when engine is hot.
Q- can anyone confirm the CTS contributing to hesitation/loss of power issues?
Q- my dash temp guage seems not to work as well. Is this related to the potential CTS issue?

thanks in advance..

Q- can anyone confirm the CTS contributing to hesitation/loss of power issues?

It can , but you would probably feel some inability of the engine to idle properly too. Hesitation can come from several areas. Lack of fuel or perhaps a vacuum leak. Have you checked or replaced the intake boot?

Q- my dash temp guage seems not to work as well. Is this related to the potential CTS issue?

"..seems not to work as well"... What do you mean?...as well as it used to?....intermittent?....Maybe you have a stuck open thermostat and the engine is not getting up to proper operating temp. This can cause hesitation as well. Does your needle stay in the cold range?

[Mikem635csi]

Q- can anyone confirm the CTS contributing to hesitation/loss of power issues?

It can , but you would probably feel some inability of the engine to idle properly too. Hesitation can come from several areas. Lack of fuel or perhaps a vacuum leak. Have you checked or replaced the intake boot?

Q- my dash temp guage seems not to work as well. Is this related to the potential CTS issue?

"..seems not to work as well"... What do you mean?...as well as it used to?....intermittent?....Maybe you have a stuck open thermostat and the engine is not getting up to proper operating temp. This can cause hesitation as well. Does your needle stay in the cold range?

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Yes, idle is not ideal :)...RPM is not stable but it's not too bad. The temp gauge is stuck in cold, but the red light (HOT!) is on all the time.
BTW had had all the coolant hoses, belts, vacuum + thermostat changed last week. All intake boots are brand new.

[CW6er]

I remember reading something about the CTS being a possible culprit in hesitation problems.

If the CTS (or it's plug) is bad, the car tends to buck and snort like it is possessed, not just a hesitation.


My cts is brittle and after driving the car for sometime, I notice tiny air bubbles coming out of cts connection to the expansion tank. Obviously something is going on there and air/coolant is escaping when engine is hot. The CTS is not on the expansion tank, it is in the T-Stat housing next to the Temp Gauge Sender and the Thermo-Time switch. What location/sensor are you referring to?

Edit: I just saw that you have an M635 (Euro Spec, right?). The CTS and other senders are on the pipe on the right side of the engine.


The temp gauge is stuck in cold, but the red light (HOT!) is on all the time.You can pull the Brown/Violet wire on the Temp Gauge Sender and see if the red light goes out (the sender is bad), if not the wire is shorted somewhere.

Pull the Brown/white wire and ground it to the T-Stat housing. the gauge should go to a full scale "hot" reading. If it does the sender is probably bad, If not, there may be a brake in the wire, bad connection or the gauge in the cluster is bad.


Yes, idle is not ideal :)...RPM is not stable but it's not too bad. The number one causes of a bad idle are vacuum leaks, the second leading cause is a vacuum leak ..... Oh yes, did I mention a vacuum leak? :shifty

Check this out: Vacuum leaks, line routing and hose size:
http://bigcoupe.com/phpBB2/viewtopic.php?p=107414#107414

When was the last time you adjusted the valves and replaced the valve cover gasket?

Edit: The link above won't be as pertinent with the M635 but the statement about vacuum leaks still holds.

[Mikem635csi]

If the CTS (or it's plug) is bad, the car tends to buck and snort like it is possessed, not just a hesitation.

The CTS is not on the expansion tank, it is in the T-Stat housing next to the Temp Gauge Sender and the Thermo-Time switch. What location/sensor are you referring to?

Edit: I just saw that you have an M635 (Euro Spec, right?). The CTS and other senders are on the pipe on the right side of the engine.

You can pull the Brown/Violet wire on the Temp Gauge Sender and see if the red light goes out (the sender is bad), if not the wire is shorted somewhere.

Pull the Brown/white wire and ground it to the T-Stat housing. the gauge should go to a full scale "hot" reading. If it does the sender is probably bad, If not, there may be a brake in the wire, bad connection or the gauge in the cluster is bad.

The number one causes of a bad idle are vacuum leaks, the second leading cause is a vacuum leak ..... Oh yes, did I mention a vacuum leak? :shifty

Check this out: Vacuum leaks, line routing and hose size:
http://bigcoupe.com/phpBB2/viewtopic.php?p=107414#107414

When was the last time you adjusted the valves and replaced the valve cover gasket?

Edit: The link above won't be as pertinent with the M635 but the statement about vacuum leaks still holds.
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Thanks for the feedbacks...

I am referring to
http://realoem.com/bmw/showparts.do?model=5531&mospid=47202&btnr=17_0035&hg=17&fg=05

#11.
The air bubbles are coming from there and just ordered the part this morning from RMEuropean ($27 + shipping). Vacuum's were all changed so not sure why still the unstable RPM (as I said earlier, its not that bad, but still should be rock solid when idling)

Valves- valve cover has a small leak and that's the next thing on my list- to change the gasket + adjust the valves. Didn't consider this may also be the issue.

[carsnplanes]

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Thanks for the feedbacks...

I am referring to
http://realoem.com/bmw/showparts.do?model=5531&mospid=47202&btnr=17_0035&hg=17&fg=05

#11.
The air bubbles are coming from there and just ordered the part this morning from RMEuropean ($27 + shipping). Vacuum's were all changed so not sure why still the unstable RPM (as I said earlier, its not that bad, but still should be rock solid when idling)

Valves- valve cover has a small leak and that's the next thing on my list- to change the gasket + adjust the valves. Didn't consider this may also be the issue.

#11 is the coolant level switch. It's simply an electronic float/level sensor. Works just like your windshield washer reservoir.
If you see bubbles, large bubbles, then you either have air the system or the system is being pressurized by combustion (Bad).
Did you order a new level sensor because you have a coolant level light on your check panel?

By the way, I wouldn't drive the car if i didn't know what the cooling system was doing. With the red overheat light on all the time, I would never really know when it was really overheating.

[Mikem635csi]

#11 is the coolant level switch. It's simply an electronic float/level sensor.
If you see bubbles, large bubbles, then you either have air the system or the system is being pressurized by combustion (Bad).

By the way, I wouldn't drive the car if i didn't know what the cooling system was doing. With the red overheat light on all the time, I would never really know when it was really overheating.
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the bubbles I see are coming under the cap..meaning the cap is not holding tight. does that make sense? Also, just got the car back from the shop a week ago having all the above stuff replaced...am just trying to diagnose the issue of the gauge before taking it back...prior to the work, the gauge was working fine.

[carsnplanes]

----

the bubbles I see are coming under the cap..meaning the cap is not holding tight. does that make sense? Also, just got the car back from the shop a week ago having all the above stuff replaced...am just trying to diagnose the issue of the gauge before taking it back...prior to the work, the gauge was working fine.

ok, but still not sure why you ordered #11 (level sensor) if your cap is bad? You should have ordered a new radiator cap (#3). It has a spring loaded seat with a gasket on it that opens at a predetermined pressure(about 16psi) to overflow tube (#4).

I would make sure that they bled the system correctly and that you are not really overheating, which is why your gauge and light really need to work.

[Mikem635csi]

ok, but still not sure why you ordered #11 (level sensor) if your cap is bad? You sould have ordered a new radiator cap (#3). It has a spring loaded seat with a gasket on it that opens at a predetermined pressure(about 16psi) to overflow tube (#4).

I would make sure that they bled the system correctly and that you are not really overheating, which is why your gauge and light really need to work.

____
bubbles are not coming from the radiator cap (which btw is brand new), but from the coolant level switch cap. I am being told that has an o-ring and may need to replace it- it basically is leaking.

Only drive the car on weekend and don't put a lot of mileage on it. Also, worth mentioning that bought the car last year-- it had been sitting for 6+ years...and has been slowly bringing it back to life as I continue to work on small things as such..

[carsnplanes]

____
bubbles are not coming from the radiator cap (which btw is brand new), but from the coolant level switch cap. I am being told that has an o-ring and may need to replace it- it basically is leaking.

Only drive the car on weekend and don't put a lot of mileage on it. Also, worth mentioning that bought the car last year-- it had been sitting for 6+ years...and has been slowly bringing it back to life as I continue to work on small things as such..

oh, ok, the "body" of the level switch. Was confused when you said it was the "cap".
Yes could be a seal or an o ring on the level sensor. Coolant shouldn't be up that high anyway....unless the leaking sensor is not allowing the system to be pressurized and then the coolant could boil out of there.

[CW6er]

Take a close look at the base of the neck that the level sender screws into. These have been known to develop cracks in the expansion tank at the base.

[Mikem635csi]

Take a close look at the base of the neck that the level sender screws into. These have been known to develop cracks in the expansion tank at the base.
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Thanks all for your responses.

I looked at the CTS and when I pulled the wire plug, the plastic connector/plug was so brittle, it broke! I can still connect it but need to find another connector piece that can help in holding it in place since vibration may disconnect/disrupt it and not even sure if those things are sold. But have cleaned it up and will test it today.

As far as the coolant level switch cap, I can tell its not holding since it does not tighten up all the way...I can also see the O-ring it old and beat up so will try to fit a custom or try to buy if possible. If the CTS needs to be changed, is it a matter of unscrewing and switching or do I need to flash out the coolant fluid? thanks again

[TJC1]

The connector repair kit can be purchased from AutohausAz, part# 1287013003, $8.26. If you need other bits and can make an order of $50.00 or more shipping is free.

You should drain some coolant out so the level is below that of the CTS, and you will probably need to bleed the system after your repair.

[Mikem635csi]

thanks all for your feedbacks...

[CW6er]

The AutoHuas kit is an OEM replacement but can be a bit fiddly. You can also get a replacement plug locally:
http://bigcoupe.com/phpBB2/viewtopic.php?p=116442#116442

http://bigcoupe.com/phpBB2/files/cts_pigtail_plug1_166.jpg

[Mikem635csi]

quick update--

I cleaned the plug and connector with a brush last night and run the car for about 10 minutes..lo and behold, the temp gauge was working albeit sometimes jumping erratically. So it seems that I probably need to change the connector/plug at some time.

Regarding the connector pic, does it require splicing the wire etc or is it an adapter type of application? Hard to tell from the picture...thx

[carsnplanes]

quick update--

I cleaned the plug and connector with a brush last night and run the car for about 10 minutes..lo and behold, the temp gauge was working albeit sometimes jumping erratically. So it seems that I probably need to change the connector/plug at some time.

Regarding the connector pic, does it require splicing the wire etc or is it an adapter type of application? Hard to tell from the picture...thx

Any new replacement plug will come with the plug and pigtails so you can splice them to your existing harness. Cut the wires as close to the old plug as possible so you don't lose too much of the original harness wire. If you're going to use butt splices, stagger the butt splice so that you don't have a mound of splice next to each other. If you will be soldering the wires, slip individual pieces of heat shrink over the wires first, then once soldered move it over the soldered repair and shrink it down.... and also a slightly larger heat shrink to slip over those two pieces. Basically each wire repair gets a heatshrink plus the whole area gets one such that you don't see the two soldered areas when done.