V6 engine coolant bridge and temp sensors

[chrisp]

After looking at the V6 engine setup in Cavaliers, Calibras and Omegas, the coolant bridge piece that sits in the V and connects the cooling channels in the 2 heads seems to be a different design in the Omega from the Cavalier and Calibra.
On the Omega, it has connections for two coolant temperature sensors - one for the dashboard gauge and the other for (presumably) both the ECU and the radiator fan. This bridge is connected to the heads at each end by hollow banjo bolts.

On the Cavalier and Calibra, the coolant bridge has 3 coolant temperature sensors - one for the dashboard gauge, one for the rad fan and one for the ECU. One of these coolant temp sensors is actually part of one of the banjo bolts - so this looks to be a bit of a specialist item.

I'm wanting to replace the engine oil cooler on my V6 engine because it is leaking oil into the coolant, and this item sits below the coolant bridge, which will therefore have to be removed first. This requires undoing the banjo bolts, including the one with the built-in temp sensor. According to Calibra owners, this special banjo bolt often snaps off when you try to undo it, so I want to obtain a spare.

Online searches for this special banjobolt/coolant sensor have so far not turned up anything. Does anyone know the part number of this item or, better, know where I can get a new or secondhand one?

[vexorg]

The special one (banjo one) on the calibra / vectra is used for the aux cooling. It controls the alternator fan, and when engine is off also controls the electric water pump and runs the rad fans at half speed.

The part on it's own went obsolete many years ago. For some reason you could buy the coolant bridge with sensors and bolts for an extortionate price.

It's the same part on the v6 vectra C, which was listed by vauxhall after it went NLS on calibra and vectra b.

There are a couple of things to think about, unless you are doing a whole loom swap then you'll need to wire your own circuit in the engine bay relay box, loom runs to the alternator fan, water pump, sensor and main fans. I've done it for three other's cars in the past, you need to understand relay logic to make it work right. If you have aircon then it's even more complicated as half speed puts the two fans in series, and full speed puts them in parallel. Most alternator fans and water pumps have died and many just leave them dead, unless you want to all working as intended then you'll need to make the call on how important this sensor is.

[chrisp]

Thanks for the advice, and I can now understand why the coolant bridge on the Omega doesn't have the third sensor, since I presume it doesn't need the alternator fan and electric water pump. My alternator fan is still working but comes on at erratic times - especially when the engine is off, when it cuts in and out randomly for a while. Also the main radiator fan only appears to run at full speed. So I guess my existing banjo temp sensor may be faulty anyway.
I've got on order a new coolant bridge kit (part no. 93177190 - I think I found the last one on eBay!) but as far as I can see from the illustration, this is coming with the two standard banjo bolts. I ordered it before I'd realised about the special temp sensor banjo bolt.
I see the coolant bridge kit with the sensor is also used on the Vectra C - is this still available at a suitably extortionate price?
Otherwise, if I do have to leave the temp sensor/banjo off because it broke when I tried to remove it, and just use the standard banjo bolt on re-assembly, will my main radiator fan still operate at full speed when required - triggered by the other temp sensor on the coolant bridge?

[vexorg]

It's only used in standaing traffic and after you turn the engine off. The alternator is tucked away and the back and has no airflow, so happily cooks itself. The rear bank of the v6 was supposed to be prone to hotspots that can warp the head when you turn the engine off, hence the electric waterpump that keeps the coolant flowing until safe. Side efffects of have the v6 rotated to be transverse.

The main fans aren't off that bridge sensor, other than when the electric pump is running, the half speed helps the cooling.

If I had kept the calibra v6, I was planning to look at fitting the vectra alternator, it's more convetional with the fan and a duct that draws air in from the wheel arch. And then ditch the alt fan and ducting.

Couldn't say on the vauxhall parts availability, but given that just about every part on the cav/calibra is NLS now, I'd be surprised if the vec c is stall available.

[chrisp]

I've now established that the part number of the temp sensor/banjo bolt is 90462372. An online search has shown that the only supplier (outside Russia) that has this item is located in Germany (Mahler). This would not normally be a problem but, because of EU-applied customs issues following Brexit, Mahler is currently not sending anything to the UK. They supply to plenty of other non-EU countries, but not the UK at present. So I'm a bit stuck.
At least one Russian dealer also stocks this item but the website is all in Russian with no translation available and, anyway, I'm a bit dubious about handing over credit card details to a Russian site. Ho hum - just one of the issues trying to run a 1993 car I suppose!

[GP123]

Hi mate, i think i had a post on this exact same sensor on the coolant bridge last year with my v6 cav. I tried everywhere for one and they cannot be got!

I ended up taking the connector out of the sensor and put 2 wires into the pins and running it into the inside of the car to a simple on/off switch and it worked a treat! you could turn the alternator fan and electric coolant pump on and off as i wished even when the car was off.

My problem with the sensor was that when the car was warm at all it just ran all even when the car was off, one day it was all still running for half an hour till i unplugged the connector at the sensor to shut it off or it would have drained the battery.

at least with the on/off switch you can control when you want it on and off, handy in heavy traffic etc on really warm days.

[GP123]

I forgot to add that the main fan that kicks in when the temp gauge reaches the red bar is it 107 or 110 degrees? it still works off its own sensor which is not related to the coolant bridge so no need to worry about it not kicking in. Thats of course there isnt something wrong with it but its not on the bridge.

[vexorg]

Yeah, the main fan is controlled by the sensor on the side of the rad.

[chrisp]

Hi mate, i think i had a post on this exact same sensor on the coolant bridge last year with my v6 cav. I tried everywhere for one and they cannot be got!

I ended up taking the connector out of the sensor and put 2 wires into the pins and running it into the inside of the car to a simple on/off switch and it worked a treat! you could turn the alternator fan and electric coolant pump on and off as i wished even when the car was off.

My problem with the sensor was that when the car was warm at all it just ran all even when the car was off, one day it was all still running for half an hour till i unplugged the connector at the sensor to shut it off or it would have drained the battery.

at least with the on/off switch you can control when you want it on and off, handy in heavy traffic etc on really warm days.

That sounds like a good idea. My alternator fan also runs erratically when the engine is just turned off - on for a period, then off, then on again etc. Just to be clear though - can you just connect the 2 pins in the sensor connector via a simple switch to start the fan and the electrical coolant pump, presumably by energising a relay?

[GP123]

yeah the wee connector that plugs into the sensor on the coolant bridge i just disconnected it and if you look in the end you can push 2 wires into this and simply have a on/off switch in the middle

[chrisp]

Thanks for the info. I'd assumed that this sensor was some kind of variable-resistance-with-temp device, but clearly it must just switch from off to on when the temp exceeds a set level.

[vexorg]

No, just a simple bimetallic switch inside. In theory you could get a similar temperature one and bolt it on to the outside of the bridge, or slightly lower temp one. Kind of like the tumble drier/oven type ones that bolt on.