Coolant Temperature Sensor Change help

Jonsey89

Hi, picking up a new CTS from VX in the morning but need to clear a few things up before i try to change.

I beleive its on the back of the engine at the right (not had chance to look yet).

Also im guessing im will need to top up the coolant (or full change) when i do this. Is there a bleed point on these engines or will they self bleed?

Thanks, Craig

astra22bertoneauto

Yes back of the engine bay to the right of the exhaust manifold on the z22se. If you are quick enough you wont get hardly any coolant leak if engine is cold.

IIRC size 13 spanner does the trick.

Gary14

Jonsey89 said:
Hi, picking up a new CTS from VX in the morning but need to clear a few things up before i try to change.

I beleive its on the back of the engine at the right (not had chance to look yet).

Also im guessing im will need to top up the coolant (or full change) when i do this. Is there a bleed point on these engines or will they self bleed?

Thanks, Craig

Follow the bottom radiator hose to back of engine you will see the thermostat housing, you will see the sensor screwed into the housing. Have the new sensor at hand, unscrew the old sensor, pop it out quickly and plug the hole with your finger for minimal coolant loss, pick up the new sensor ready to fit, remove finger quickly install new sensor again for minimal fluid loss. Remove expansion cap give the bottom hose a couple of sqeezes to expel any air, top up fluid as required, replace expansion cap, run engine check for leaks

The cooling system is self bleed.Whenever i do any work on the cooling system i top up the coolant, leave expansion cap off, let the engine run until luke warm thermostat open giving all hoses a squeeze to expel any trapped air, take the car for drive, back home leave car idling and wait for radiator cooling fan to cut in, you may see the coolant go down in the expansion bottle when the fan is running. Turn off engine and leave until engine cold. Check for any leaks aoround newly fitted componants, if ok top up coolant as required.
:thumbup:

Nik_L

astra22bertoneauto said:
Yes back of the engine bay to the right of the exhaust manifold on the z22se. If you are quick enough you wont get hardly any coolant leak if engine is cold.

IIRC size 13 spanner does the trick.

Its a 19mm spanner.

Ratchet spanner ftw when changing the CTS.

astra22bertoneauto

Nik_L said:

astra22bertoneauto said:
Yes back of the engine bay to the right of the exhaust manifold on the z22se. If you are quick enough you wont get hardly any coolant leak if engine is cold.

IIRC size 13 spanner does the trick.

Its a 19mm spanner.

Ratchet spanner ftw when changing the CTS.

Sorry. cant believe i put 13mm - definately got crap memory. But yes ratchet spanners are king!

Jonsey89

Thanks guys, job done i no time. Warm start problem still there though. Any suggestions?

Could an old chain cause this? Even tho its only when warm.

Polibon

Hi, I have a coolant temperature warning light on permanently now, for the last week, though my temperature guage reads correctly and the car seems to drive fine. Another forum suggested this device could be the cause...or wiring.
Could this be the cause? Someone suggested I short the sensor wire to the block and see if light goes out to see if wiring is ok. Got any other tests?
BTW, my engine has 158k miles on it and still runs like a dream.
Thanks,

comet

Polibon said:
Hi, I have a coolant temperature warning light on permanently now, for the last week, though my temperature guage reads correctly and the car seems to drive fine. Another forum suggested this device could be the cause...or wiring.
Could this be the cause? Someone suggested I short the sensor wire to the block and see if light goes out to see if wiring is ok. Got any other tests?
BTW, my engine has 158k miles on it and still runs like a dream.
Thanks,

There are two sensors. One is the little one (about 11mm I think) with a single wire going to it. That is what operates the temperature gauge. The other one is down the back of the engine (as said above) 19mm (I use a ring spanner sawn in half - too poor to afford rachets 🙁 ) has two wires running to it. This one sends a signal to the ecu to tell is the engine is warm so it leans the fuel/air mix. If it goes wrong the engine runs too rich - like the old auto chokes when they stuck on.

The putting the wire to earth test is for the first one. When you earth the wire the gauge ought to read hot.

To test the second one you measure the resistance cold, then hot, but I can't remember what the exact readings are (Google it). They are only a tenner. One way to tell is get the engine hot, turn off, then try a hot restart without touching the throttle pedal. If it starts OK then that sensor is usually fine.

I have no idea where the feed for the coolant warning light is - mine doesn't have one! Poverty spec rules - far less to worry about.

Polibon

Hi Comet, thanks for info. As an electronics engineeer, it would make more sense if the sensors you mention were the other way around, and the 2 wire sensor feeds the gauge (so resistance varies the dashboard reading) , and the single wire one just provides a flag to the ECU, but armed with this knowledge it will be easy to unplug one and see what happens. I will report back :thumbup:
Cheers,

astra22bertoneauto

comet said:

There are two sensors. One is the little one (about 11mm I think) with a single wire going to it. That is what operates the temperature gauge. The other one is down the back of the engine (as said above) 19mm (I use a ring spanner sawn in half - too poor to afford rachets 🙁 ) has two wires running to it. This one sends a signal to the ecu to tell is the engine is warm so it leans the fuel/air mix. If it goes wrong the engine runs too rich - like the old auto chokes when they stuck on.

I didnt realise that the z22se has 2 sensors notsure.gif I know of the one down the back of the engine, where is the other one located?

Would the sensor down the back not be able to report the temp to the ecu & the gauge? doesn't seem logical to have 2.

Gary14

Only has one sensor :thumbup:

comet

My apologies, my mistake. I'm usually working on engines which use 2. tbh I've never had to touch anything on my own so I just assumed it used the same system. In which case change the one 19mm sensor, they're not expensive.

MikeS

air temp sensor on air intake pipe from airbox to throttle body

coolant sensor on thermostat housing back of head next to EGR valve

yorkie200

MikeS said:
air temp sensor on air intake pipe from airbox to throttle body

coolant sensor on thermostat housing back of head next to EGR valve

If it was the air sensor on the intake pipe, it would throw an EM light up. mine has to be turned 45 degrees to stop light coming on.

Have you any em lights? codes?

you could have been sold a faulty new sensor! has been known. try putting the old one back on and see if it runs better. that way you know that it is faulty and that you haven't knocked something.