Throttle Body coolant hose for flushing/bleeding purpooses
 

I didn't want to create a thread for this because I'm sure it has been covered but I've looked around the forums and can't find a picture to locate which hose it is or if its necessary.

I'm going to be installing a KOYO N-FLO rad along with most of the related cooling system parts( Thermostat,Water pump, hoses etc...) so I want to do a thorough coolant flush as well. I found plenty of info for the coolant flush, including the location of engine drain plug located on the left side of the engine. I see quite often mentioned that there is a throttle body coolant hose that you want to unplug.

Just a couple questions, does anyone have a picture or can describe this hose so I know which one it is and locate it? Also which end to unplug it from?

Second, Is it really necessary or that beneficial to unplug this hose for bleeding purposes? I am already going to be using the Lisle No Spill funnel to bleed the system.

The hose I unplug is the one that attaches to the top nipple of the throttle body, next to the firewall, highest point in the cooling system. You should be able to see it without removing any parts. Disconnect it during the refill process to help purge air from the cooling system - you can get quite a lot of coolant in fairly quickly with the hose disconnected, but not a 100% fill. I have never tried to do a fill without removing this hose, but I imagine it would take considerably longer to get the coolant in and the majority of air out.

Personally, I have never used the block drain, only the radiator drain. But I am doing annual coolant flushes so I figure the little that remains in the block will get purged next time and the coolant never gets that bad since it is frequently flushed. Annual flush may be excessive though...

Exactly what I do - quick, easy, and has worked for 25+ years.

Disconnecting the throttle body coolant line and filling slowly will help a little, but a Lisle coolant funnel that seals to the fill neck will do a much better job. I have the Lisle 24610 kit , should be easy to find online and at some auto parts stores.


The block drain is easy to access if the car is on a lift, but probably a huge pain if you're working on ramps or jack stands. It will get a significant amount of additional coolant out of the system after the radiator drain has run dry, I'm guessing about 1.0L of coolant.

Awesome, thanks man this is the answer I was looking for!

I think I see the hose you're talking about, I'll include a pic and highlight it so you can double check it's the right one.

And to just get the right understanding, I disconnect it when I'm refilling with the engine off correct? Then once it's initially filled do I reconnect it before starting the engine and begin to bleed out the air ? Or do I leave it disconnected until after I bleed out all the air?

Yea I just got the car and since I'm doing a bunch of cooling work I minus will take out the engine drain plug and fully flush her out, but I feel you, if I do it annually I won't bother with the engine drain plug either.https://cimg4.ibsrv.net/gimg/www.rx7...11a24a939c.jpg

Nice, I'm new to the rotary life so I was completely unaware of this. I'm glad we have such a helpful forum community.

Yea brotha, luckily in the Cooling threads they advise to get that funnel. I just received it actually, the same one Lisle 24610 less than 20$ on amazon!

Really? I haven't looked for it yet, I have her on stands, hopefully it's not that much of a pain in the ass. I do want to do a thorough flush.

Since getting a Lisle funnel, I don't bother with the throttle body coolant line anymore.

This picture is not great, but should help give a general idea where the drain plug is. I think it's a 14mm bolt. Even with the radiator completely empty there is going to be a good amount of water pressure when you first remove the bolt, and unfortunately there's not a great path around that area so plan for coolant to spill everywhere and drip all over the subframe.

https://www.rx7club.com/attachment.p...1&d=1520408854

Yea that's a good point and that's why I bought that funnel kit. I mean if it's the hose that I took a picture of and all you have to do is disconnect it from up there that wouldn't be a problem. I just want to understand the procedure; do I disconnect it when I do the initial fill and then reconnect it, start the engine and do the normal bleeding with the funnel kit? Or do I leave it disconnected while I start the engine and do the bleeding with the funnel kit ?

Awesome, thanks for the pic! It gives me a better understanding, and thanks for the heads up about the prrssure brotha. Yea that sucks, I don't want to get coolant everywhere but I mean since I just bought the car and I'm changing the water pump, thermostat and radiator I'm thinking I should. The coolant it has now is actually really clean, it was just replaced by the company I got her from, but since I don't know what ratio or brand coolant they used I want to flush it all out, but if it's too difficult to get to I'll just leave it... With my regular bi-annual flushes I definitely won't be removing it haha

Also, use 50-50 distilled water and ethylene-glycol (green) antifreeze. It's the only type that works correctly in the FD.

Yea I have it, thanks for pointing that out to Me! I just wanted to be sure of what I was doing and ask the communuty before I went at it, mainly the procedure.

Ah yea that's the pic that I saw online somewhere, thanks for posting it! Yea since its my first time I want to drain as much as possible, but with the annual or bi-annual I will only drain from the radiator as well. I'm going to be using the Mazda FL22 full strength, still haven't decided on the ratio yet.

Agreed.
Antifreeze actually loses some of its properties if it's not diluted at with at least 40% water. However, for corrosion protection I'd use at least 30% AF to 70% water. I'd not trust that there would be enough anticorrosion chemicals to be effective at 20% concentration. OEM's recommend 40 to 60% AF.

Awesome man, this is exactly what I was looking for. You know my car is red so I might do that for Christmas to get a nice look going on in my bay hahaha. I know it sounds like a stupid question and I was pretty sure I would have to reconnect before starting it if not it would start coming out of there, but I just wanted to be sure.

That's a good alternative, but yea I already got the Lisle funnel so ill use that.
Thanks for your help, I appreciate it.

Exactly!! I was planning on doing a 70/30 water to coolant, for better cooling efficiency and still some decent freeze protection since it could get really cold here in the Springs.

Thanks again brotha!

Yea I was able to find some good threads about the coolant for our rotary engines. Im going to be using the genuine FL22 full strength and plan to do a 70/30 water to coolant ratio.

Yea that's true, I plan on doing a 70/30 ratio for that reason. I've read some guys running all water with water wetter?? I'm sure there's a performance reason to it, but for now I wouldn't dare do that.