Chargecooler - To Expansion tank or not

[DottySkee]

Hi All,


Been reading up on the expansion tank for the ST205 chargecooler and I'm a bit split on what to do. I don't have the expansion tank, it wasn't used on the setup the chargecooler came from but having read a lot about the water level loss etc. I'm now wondering if it would be worthwhile to get one.
If my system is set up right, should I not need one? Just leaving the hose from the filler cap going to atmosphere?

I'm also just running a Rev 3 ECU so no ST205 ECU to take the reading from the level sensor. I was thinking of wiring this sensor to either a light in the cabin or a guage for water level to monitor this, espeically if I don't have the expansion tank.
Is it possible to be able to wire the sensor straight into a gauge or warning light to monitor the level? What sort of signal does the sensor give?


Thanks

[shinny]

The sensor is just a level switch... it's closed when the coolant level is ok and open when it's too low. So to light up a warning light, you'll need some form of 'NOT' circuitry. (There are all kinds of ways of doing that we could talk about, depending on what light you want and how good your electrical skills are)

As for the expansion tank, the system wants to draw in liquid as it moves water (that's the bernoulli effect), and the rad cap will suck in whatever it is connected to. So if you leave the pipe from the cap vented to atmosphere, you'll suck in air every time the pump starts. So your options are to leave the system sealed by sealing that pip form the cap, or running with a reservoir. It makes sense for the system to have a small reservoir which is why Toyota fitted one, and explain that the system should be topped up while the engine is running and the throttle has been blipped to turn on the pump. (If you're not using the ST205 ECU, that probably just means "with the ignition on" for you)

[DottySkee]

The sensor is just a level switch... it's closed when the coolant level is ok and open when it's too low. So to light up a warning light, you'll need some form of 'NOT' circuitry. (There are all kinds of ways of doing that we could talk about, depending on what light you want and how good your electrical skills are)

As for the expansion tank, the system wants to draw in liquid as it moves water (that's the bernoulli effect), and the rad cap will suck in whatever it is connected to. So if you leave the pipe from the cap vented to atmosphere, you'll suck in air every time the pump starts. So your options are to leave the system sealed by sealing that pip form the cap, or running with a reservoir. It makes sense for the system to have a small reservoir which is why Toyota fitted one, and explain that the system should be topped up while the engine is running and the throttle has been blipped to turn on the pump. (If you're not using the ST205 ECU, that probably just means "with the ignition on" for you)

Thanks for the reply Shinny.

Basic electrical skills but my Dad is an electrical engineer so he can check my work and guide me. I'd not look to do anything too fancy. Either a green and red light so that when level is ok green is lit, level too low red is lit. My thinking being, if there is an issue either both or neither light will be lit. Other idea is just a red light, out if level is ok and lights up if level is too low. Only thinking is, if there is an issue and light does come on, I may jsut take it as the level being ok.

Just googled Bernoulli effect, learn something new every day! I should really get an expansion tank then. There's one on ebay for £15 which isn't too bad.
For setting it up, I looked at the guide and the expansion tank doesn't get metnioned really. Possibly means I'm missing something obvious but where does the second outlet on the expansion tank go to?

[shinny]

You want to connect the pipe from the core's rad cap to the bottom port on the expansion pipe. This helps the system bleed by making sure it will always draws in coolant (if any is present in the tank) even though it might expel air.

[Lefty1991]

I'm just building my chargecooler setup.
To have a light come on when the level gets too low you will need a normally open relay, this will then allow 12v to the led when the level switch goes open circuit with a low level.
If you need a diagram send me a pm

[SteelMistAlex]

I did this to mine about 6 months back.

No expansion tank, and I plumbed the expansion pipe into the main coolant system (low pressure side) with a t piece so it can suck from the expansion tank.

No problems so far (many thousands of miles later) and the level has never changed.

Just bleed it THOROUGHLY when you install it.

Btw I also liquid gasketed and double jubilee clipped all the joints - easier to do it right first time than chase leaks later.

I'd also recommend a new pump. Mine (second hand gt4) failed within a month so put a bosch high flow one in and it works a lot better.

Just my experience, and Btw while a ball ache to install (2 full days in my dad's workshop, but then we also changed aircon rad) totally worth it

Alex

[DottySkee]

You want to connect the pipe from the core's rad cap to the bottom port on the expansion pipe. This helps the system bleed by making sure it will always draws in coolant (if any is present in the tank) even though it might expel air.

As son as I posted that, I realsied that it would be connected at the bottom so that it actually drew fluid! Thanks for the help, got a tad confused with it all! Got the expansion tank ordered so that will be here in 2 days for the engine going back in this weekend

Connecting it to the main coolant system is a rather good solution actually! Hadn't thought of that at all but I ordered another expansion tank now. I will however be making extra sure all the joins are sealed tight. 19mm hose is on the 21mm ends though so they are proper tight!

I'm going to have the pump mounted in the usual place on the gearbox so it won't be too hard to swap out if it does let go. I'd stick a nice one on at that point but my money is going towards getting the engine running and cage/buckets/harnesses in before April. Take a chance the pump doesn't let go before then

A diagram would be excellent actually, PM on it's way.

Thanks for the help chaps, I'd be totally stuck without IMOC

[shinny]

No expansion tank, and I plumbed the expansion pipe into the main coolant system (low pressure side) with a t piece so it can suck from the expansion tank.

I'm not sure that's a perfect plan. I mean, it's a simple solution but not optimal.

Why? Well, if you have a system that turns the pump on and off (as the ST205 ECU does) then there's a reasonable chance that your charge cooler system could ingest some hot coolant from your engine.

[raptor95GTS]

as shinny says, the car coolant is running near or over 100degC so thats pretty damned hot compared to anything the chargecooler should be getting from the incoming air. It might work ok but it wont be the better solution that already mentioned by others on here

[SteelMistAlex]

True, but it can only suck from the expansion tank which is at engine bay temp and I don't think it has ever actually sucked anything in, it was more to vent it out.

The fluid never gets that warm in the cooler and there is an air gap to allow expansion.

I filled it so it couldn't flow over the internally baffled shelf to make sure it all flows through the core.

Appreciate it's not ideal though, just with my cai I didn't have much room for an extra tank in the bay.

Not questioning people's point btw - it was a short term fix that I've use never felt needed rectifying.

And if you have a water temp gauge like I do I just over ride the pump and it drops the temp pretty dam quick - love my pump - about twice the flow rate of the gt4 one


Let me know where you fit yours though, and if yours does suck (to coin a phrase )

A