Hi guys, I've noticed a coolant leak somewhere around the throttle body, so rather than muck around disassembling the throttle body, I'm just doing to bypass it

While I'm at it, I'm going to change out the coolant, replace thermostat and possibly some of the other hoses depending on condition - and also really give the radiator a good flushin'.

This is the first time I'm removing the thermostat to do a proper coolant flush on this car, though, and it looks a bit trickier with the V6 (KF-ZE) than the 4-cylinder models as it's in a tricky position and connected to the lower rad hose rather than the top like I'm used to!

First step is to disconnect bottom radiator hose (I don't trust the radiator stopcock not to break on me), and drain into bucket. BUT, I'm keen to flush the block out too but the thermostat's in a dog of a place (see http://mazdaepc.com/parts/323F/AEBM03/E2/1500%20B/). As soon as I loosen that, coolant's going to start pouring out all over the place, surely? The tranny's sitting right below... Any tips to lessen this? Or... is there a separate drain plug? Or... am I going about this entirely the wrong way ?!

Thanks for the advice!




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The throttle body coolant pipes will cause higher tick over if it gets bypassed and will mess with fuel mixture. I did the same thing and regretted it within a week. Lower mpg etc and engine constantly runs like its got an old fashioned choke on. If you turn the revs down when warm to compensate for the bypass it will cut out when cold. leave the radiator caps on when you disconnect the bottom rad hose. you'll be surprised how slowly it drains but caps off it will gush out.

Hi Brucey, thanks very much for the reply. Yes good call on leaving the caps on - do you have an idea of how to avoid the gushing out of the thermostat housing when I remove the thermostat, though?

Re: Throttle performance - I'm in the slightly warmer climes of Auckland, New Zealand - so do you think I'll still suffer those problems you mention? I'm tempted to plumb in a couple of T-pieces so I can switch between bypassed and non-bypassed and try it out!

Hi Chris,

To limit the amount of coolant spilling all over your tranny.
Remove one end of the thermo housing hose.
(take the end off that connects to the rad) place in bowl/bucket ect
drain as much as u can, Then jack car up from back drivers side, this will help just a little.

Hope that helps mate

may not have as much of an effect but only you will be able to tell, its not going to be an irreversible experiment, one of the pipes on mine was long enough to do the bypass anyway but after i felt the difference in the performance and wallet i just replaced them to how they were supposed to be with new pipe.

Thanks guys - I'm out of town for a few weeks but will let you know how I get on when back!

Sorry to jump in on this, but why does the throttle cooling bypass affect idle?

The "cooling" has the opposite efect to the sucked air entering the TB.
The water(cooling liqud) is at aproximately 95-98C degrees at work T, that way it warms the tiny little ports that the air is going through.If the humidity is higher the air passing those holes can create ice and reduce the flow when the temperatures are colder... that is why you need warming the TB idle rpm ports..
Well, that's my explenation really..
And i'm thinking that i may have problems at winter

Hi guys, just a quick update - I did the bypass mod, seems fine - haven't noticed any changes to idle behaviour.
Absolute dog of a time removing and reattaching some of the hoses in the hard-to-reach spaces - are there any lubricants that I can use in future to make this an easier job?

Anyways, here are the steps I followed (Lantis V6 2.0L):
1. Jack up car, jack stands.
2. Try to undo radiator petcock. Struggle to get decent purchase, worry about it being brittle and breaking, decide to back off. Give up in frustration.
3. Try to undo bottom rad hose from rad. Curse Mazda - bloody nightmare to get at "old-style" radiator clamp and hose itself. Give up in frustration.
4. Undo bottom rad hose from engine end (the metal pipe which connects to the thermostat housing). A little bit of spillage from around the thermostat, but nothing major. Manoeuvre hose downwards and collect old coolant in basin under car. Empty rad.
5. Turn attention to throttle body hoses: Hose A (engine to throttle body) and Hose B (throttle body to thermostat housing). First, remove air filter housing to get a bit more room to move. Remove Hose A entirely (allow coolant from block to drain all over tranny, then eventually into basin). Disconnect Hose B from thermostat housing, and fold Hose B around so it's connected to throttle body at both ends (seemed tidy). Take new hose (Hose C) and with great difficulty connect to engine side, then with great simplicity connect to thermostat housing.
6. Remove and clean filthy overflow bottle. Use in turn: hot water & raw rice, hot water & baking soda, pressure washer my neighbours are cleaning their house with. Get best results with hot water & oxy-action cleaner. Be lost for words with the sheer quantity of rusty crap that comes out through the entire process. Incredible.
7. Disconnect top rad hose from engine side, stuff hose and rag in, and run hose until water runs clear.
8. Disconnect "other" top rad hose (leading from rad to overflow bottle), repeat hose trick.
9. Do #7 again, was worth it, got more brown out.
10. Re-fit overflow bottle.
11. Reconnect all hoses (ie. top rad hose to engine, bottom rad hose to engine, top rad-overflow hose to overflow bottle).
12. Refill coolant, realise with a wince that I'm going to have to do this again in a few months when I pull out engine for cambelt replacement.
13. Take care for test drive - all seems fine!

EDIT 14. Wake up next morning and realise I didn't flush engine block and heater core properly before refilling coolant. Sigh!!

You can always do the cambelt with the engine in place but use a timber packer and the supplied car jack to support the engine on the cambelt side so that you can remove the engine mount. Done it 3 or 4 times now. Hardest bit is probably the plastic covers...