Stock 240 coolant gauge + whiteblock swap = ?

I hate asking questions on forums, because search usually answers everything...but this time I just can't seem to get the right phrasing. What's the best way of getting the stock 240 coolant gauge to work with a whiteblock swap? Ideally I'd like to have the 240 gauge sensor mounted before the thermostat, so I could see it warm up, but I'm not sure I want to tap my thermostat housing...since they're definitely not growing on trees around here. I've considered mounting it after the thermostat, but I don't like the idea of the gauge only reading after the car warms up.

I'll be using my MS2 v3.57 for management, with the stock coolant sensor, but I really don't want to have my tablet/phone on all the time just to see the engine temp.

[SOLVED] see post #16 for the resolution

So... I don't know the whiteblock very well, but of course on the 240's there are 2 sensors. One is reporting temps to the ECU and the other is sending temps to the gauge.

If you're implying that the whiteblock doesn't have this gauge sender... then I might suggest looking to Saab (or anyone) and place a piece of pass through pipe in whichever the correct coolant line is and tap that for your correct sensor.

If the whiteblock has the hole, but it's not correct threading or something... my logic would be to simply adapt the threads, and run the redblock sensor. On the redblock... and someone will correct me if I'm wrong, but all of the gauges are essentially reading isolated circuits and not related to the ECU aside from speed and RPM. Coolant and fuel are reported on their own though.

The B6304S I'm using has a coolant sensor for the ECU in the thermostat housing, but no separate one for the gauge. Since I'm using megasquirt, I'm going to be hijacking that sensor. There's no place before the thermostat to put a sensor to run the gauge. I could easily put it after the thermostat, but then the gauge would only read correctly after the car hit operating temperature and the thermostat opened. That's what I'm trying to avoid, mainly because I love having a properly functioning cluster.

I see all kinds of whiteblock swap threads, but there isn't much info on how everyone is handling their cluster functions. I really don't want to drill and tap the housing, since I'll inevitably crack it or destroy it completely, lol.

What is the part # for the B6304S sensor? Any other specs you have like resistance or voltage ranges could be helpful too.

Broke4speed said:

The B6304S I'm using has a coolant sensor for the ECU in the thermostat housing, but no separate one for the gauge. Since I'm using megasquirt, I'm going to be hijacking that sensor. There's no place before the thermostat to put a sensor to run the gauge. I could easily put it after the thermostat, but then the gauge would only read correctly after the car hit operating temperature and the thermostat opened. That's what I'm trying to avoid, mainly because I love having a properly functioning cluster.

I see all kinds of whiteblock swap threads, but there isn't much info on how everyone is handling their cluster functions. I really don't want to drill and tap the housing, since I'll inevitably crack it or destroy it completely, lol.

Click to expand...

I see where you're going here but also...

The gauge would always read correctly. If your thermostat failed, it would probably read low rather than hot I guess but... ideally, with the cycling of the tstat you'll have an idea of your temps no?

Hmm... you staying NA? And/Or what about putting something in line with the heat exchanger? One of those lines would be full engine coolant temp no?

Here's what the 240 gauge is expecting to see:



The part # is 460191. Same part from 1975-1993. It's resistance based which means the gauge is putting out 12v.

I'm sure it's possible to build a circuit which converts your reading to drive the gauge, but how complex and expensive that'll be will depend on what exactly the B6304 gauge is outputting.

Most likely it's going to be easiest to splice in the coolant sensor somewhere. This guy says there were two sensors on earlier model B6304s. Perhaps you can tap the head in the old sensor location and just screw in the 240 sender there?

I can't be of much help other than the temp gauge on the white block does show warm up.

Do you have the white block installed? I've seen pics of the 6304 in the 240 and the 780, and it looks right at home in either.

EivlEvo said:

I see where you're going here but also...

The gauge would always read correctly. If your thermostat failed, it would probably read low rather than hot I guess but... ideally, with the cycling of the tstat you'll have an idea of your temps no?

Hmm... you staying NA? And/Or what about putting something in line with the heat exchanger? One of those lines would be full engine coolant temp no?

Click to expand...

The stock redblock temp sensor is in the head, pre thermostat, which is ultimately what I'm trying to emulate. I could definitely put it after the thermostat, but until it opens, it won't really show accurately on the gauge. I'm just worried that if the tstat doesn't open, it'll start to overheat, but I won't know it because the sensor will still be seeing cold coolant.

I hadn't thought about the heater core lines. There is one that comes off the back of the head, which would be full engine temp, definitely.

Khrrck said:

Here's what the 240 gauge is expecting to see:

The part # is 460191. Same part from 1975-1993. It's resistance based which means the gauge is putting out 12v.

I'm sure it's possible to build a circuit which converts your reading to drive the gauge, but how complex and expensive that'll be will depend on what exactly the B6304 gauge is outputting.

Most likely it's going to be easiest to splice in the coolant sensor somewhere. This guy says there were two sensors on earlier model B6304s. Perhaps you can tap the head in the old sensor location and just screw in the 240 sender there?

Click to expand...

My engine is a 94, and it has the rear sensor as well as the front. It's super tight back there, since it's a swap, but I might be able to use that coolant sensor for my megasquirt and pirate the front one for the gauge location. I was kinda hoping not to use that rear one though, since if it ever goes, it'll be a bear to get at, lol.

On my car, I use the coolant temp sender in the thermostat to provide coolant temp to megasquirt, and then output from megasquirt to the gauge cluster. Simple and works just fine.

Jacob (Homer) just used the 240 one and had it retreaded to fit in the back of the cylinder head. http://forums.turbobricks.com/showpost.php?p=4124913&postcount=1081

Or:

Use the me7 (99+) thermostat housing. It has the temp sensor and another port for an additional coolant line the later heads use. If not using that, put second temp sensor there.

Or do what Tom ^^^ did.

The standard B230 LH2.4 temperature sensor is actually 2 sensors in one housing. It has 2 pins and uses the block for the grounds. With LH2.4, one goes to the EZK box and one to the ECU box. There's a separate B230 temperature sensor (1 pin) just for the gauge.

I don't know if the LH2.4 sensor will fit the hole in the whiteblock, nor if the temperature curve is the same as what the gauge wants. Maybe find a Bosch catalog and compare part numbers and specs? Or look for a gauge&block compatible 2-pin dual sensor.

VW golf my83 temp sensor works with 240 temp gauge and fits in thermostat housing. I' ve been told.

Hank Scorpio said:

Jacob (Homer) just used the 240 one and had it retreaded to fit in the back of the cylinder head. http://forums.turbobricks.com/showpost.php?p=4124913&postcount=1081

Or:

Use the me7 (99+) thermostat housing. It has the temp sensor and another port for an additional coolant line the later heads use. If not using that, put second temp sensor there.

Or do what Tom ^^^ did.

Click to expand...

Amazingly, before I saw this post, I happened to find an ME7 V70 at my local yard...and snagged the thermostat housing. One port is M10 and the other is M12, so I'm going to rethread the B21 gauge sensor for one of those ports on the lathe at work .

The PWM option is cool, but my MS2 can't really do what is required, and I don't really want to upgrade just for that. Future plans though .

OttoB said:

VW golf my83 temp sensor works with 240 temp gauge and fits in thermostat housing. I' ve been told.

Click to expand...

This is another option. The stock B230 sensor goes up to 120*C, and the VW one you mention goes to 125*C, so it would be really close. I might give that a try, since I'm pretty sure I have one already and it's M10 threaded.

[SOLVED]

The VW single-pole sensor (part number 027 919 501, various models. I found it on a 91 Passat 2.0 16v, but it's the same as the 83 Rabbit one mentioned above) has a listed 125*C limit, which will be good enough to keep everything close to accurate. The sensor I got has that part number, but 120*C listed on the sensor itself. I'm going to give it a try. I also grabbed a Delphi/GM coolant temp sensor from an LS* engine, which I THOUGHT was going to be a 1/8NPT fitting...but it turns out to be M12x1.5 (or the NPT close-enough-equivalent). The 99+ ME7 thermostat housing, which has two ports, has one M12 and one M10...which is great! Now I have a GM CLT for the MS2 and a CLT for the stock 240 gauge, and it took no modifications to anything.

[summary]
99+ ME7 thermostat housing has two ports. One M12 and one M10. VW/Audi part # 027 919 501 fits in the M10 and goes to the gauge, and a GM coolant sensor from virtually any LS* engine seems to be M12, and fits the other port perfectly. No fuss, no muss.

A picture.