Thermowax issue?
 

when i start and drive the car from overnight-cold the idle will hang out at 1500 unless i drive for like half hour then it will come down to normal.

Also say if i just run to the store when i come back it will idle low like it should (700-ish) almost as if the car isnt running hot enough to melt the thermowax. the car has a 177 degree t-stat in it but the valve is supposed to melt at 77, not 177.

I presume that letting the car sit while im at the store it heat-soaks the valve and gets the thermowax to actually melt?

has anyone had this before? is this a common sign of a failed valve?

im not looking to bypass it as i kind of like the fact it does what it does.

77 Farenheit or Celsius?

thermowax is just a term, it's not a wax exposed to atmosphere... i don't know the exact inner workings of the unit but it isn't going to melt down on an engine like you think it will(in mid summer engine bay temperatures easily exceed 230F).

the opposite is likely true, you probably have a small air pocket in the cooling system which sometimes works its way through the thermowax to allow it to function normally, on short drives it is not registering engine temperature and is holding the throttle up.

feel the hoses going to and from the thermowax when the engine is to operating temperature, the hoses should be only slightly cooler than the upper radiator hose if coolant is flowing through it normally. it is common for calcium to build up inside the passages through the thermowax and stop coolant flow intermittently.

and lastly sometimes the thermowax just becomes sticky, grab the throttle cam on the front of the throttle body and force it closed several times to see if the thermowax becomes functional again.

satch...77 F. at least thats what the service manual says. 25C 77ish F.


i know its not exposed to the air and no its not a term. its a wax pellet that melts letting the plunger drop. None of what you said really seems to be whats going on other than the try reefing on it when warm to see what its doing.

when i had the UIM off it seemed to be moving freely and i adjusted it slightly. i may just back it off even more so it idles at like 1000 cold just so its not so annoying.

ill run it with the cap off for a few minutes to see what happens. see if i cant get that air bubble to pop out if there is one. however i doubt there is as the hoses feel warm when they should and cold when they should. and warm on both sides of the valve not just one, which would suggest a clog.

the last couple cars i've had have had stuck thermowaxes, because the hoses were full of crud/junk cleaning the hoses, and burping the system fixed em.

i also do like to adjust the thermowax so that it turns off a little quicker, we have mild winters here, and i really only need the high idle for about a minute, and not 5...

all my coolant hoses are new as of 100 miles ago

replacing the hoses doesn't get rid of the junk that clogs up the inside of the thermowax, or the port at the rear iron.

you could remove both hoses from the throttle body, attach a lead hose and blow into it and see what comes out, if anything.

I just pictured me painting the garage with old coolant junk. ew

ok, so reviving this thread.


i have determined that its 99% likely that the thermowax is not operating under water heat, but general under hood temps. so the coolant isnt properly flowing through the different cavities on the UIM.

when i did the vacuum hoses i rigged up a longer hose with a fitting in the middle so i wouldnt have to deal with re-attaching that keg-throttlebody hose so i can get to the "intake" side of the thermowax valve without removing the UIM.


which hose is the "exit" hose? i want to blow out the junk and i need to know which hose to unplug to let all the crap out.

the coolant path is back of water pump -> BAC valve -> either thermowax or throttle body, depending on turbo or NA -> thermowax to top rear of engine.

oh, i thought it flowed the other direction. either way i doubt it matter which end i force air into as long as the other end is open.

thanks

no idea which way coolant flows, doesn't matter as long as it can flow.

following up on this,


i took off the UIM this weekend and found that the thermowax valve was completely blocked. couldnt blow it out either. the blow gun i was using had one of those safetys that when a certan back pressure is reached it vents to the atmosphere.

I also had to take a small screwdriver to the passage way to "break" all the scale out. and i found a loose charge pipe which could have yielded some weird idle issues.


Also i think this is why it idles funky. the thermowax EVENTUALLY retracts due to underhood temps but the BAC still isnt getting the proper temp coolant so it thinks its in cold idle while the thermowax says hot idle.

the BAC doesn't get any coolant flow, a loose intake pipe may give a vacuum leak and idling issues though.

wrongola big chief. it comes off the backside of the waterpump housing.

you're right, most of the time that bolted on line is deleted.

but i doubt that line missing is causing the BAC to malfunction, it seems to be more for extreme climates to warm the valve in freezing temperatures.

I don't think you have any idea what's going on Here.

What are you talking about? The BAC doesn't sense a cold engine from a warmed engine by the temp of the coolant. The BAC is just a solenoid devoid of any temp sensing abilities as it gets its input from the ECU. There are but two wires connected to this solenoid as one is a voltage signal while the other is an operating signal wire and this signal wire is an output wire from the ECU and not the BAC, thus the BAC only inputs information as opposed to outputting.

The BAC is a solenoid valve controlled by the ECU. It's commanded by the ECU electronically via a duty cycle signal.

The coolant line is just there to prevent the valve from icing up in very cold weather and has no effect on the actual operation of the valve (unless it's freezing, of course).

The thermowax is a mechanical plunger which pushes on the throttle shaft to open it up. Purely mechanical, based on coolant temperature. If the thermowax is pushing the throttle open, the ECU typically (I say typically because at cold start it does, or if the TPS is misadjusted) will not try to use the BAC to regulate the idle.

However I'm fairly sure the same hose feeds the BAC as the thermowax. So if one of the coolant feeds on one of the devices is blocked, the thermowax won't function properly.

in almost all cases the BAC works or it doesn't at all, there isn't much in between with it. so with that said it doesn't cause erratic idle issues if the list below has been performed, more often than not that is caused by an electrical issue from a sensor/fuel pump wiring or a vacuum leak.

most FCs just don't run right because someone has worked on the car previously and not reassembled it correctly or addressed important areas such as engine ground straps. most common than anything else is simply vacuum leaks because reassembling everything without creating one isn't always an easy thing to accomplish.

then there is the proper way to tune the engine run at it's set parameters:

1) set the timing by dropping the idle below 1k RPMs and set the timing first before anything else
2) set the idle speed by jumpering the set connector and then set the curb idle speed
3) adjust the TPS to read 1 volt with the ignition on, throttle closed and engine warmed

but if you want to be a smartass i will just put you on ignore. yeah you caught me at a brainfart moment but there's probably no one on the planet besides a factory assembly technician who has worked on more FCs.

for vendor you sure are an asshole. go ahead and ignore. dont need your help.

very well. i also don't need to waste time giving free advice to a punk kid.

whatever. just delete your account if you have such a hard time helping people without being a huge dick about everything.

MODS:
do me a favor, delete all his posts in my threads. none of them are vaguely helpful, or if they are its after like 9 posts trying to wrench something out of someone that doesn't want to help in the first place.

i find irony in that i have done nothing in this thread but to help you, but i can't see your posts going forward so you won't have to worry about it anymore.

heads up, just got a call from mazdatrix that the gasket is no longer available from mazda. however it looks like its just rather normal gasket paper and nothing special. i plan on cutting my own from a sheet of gasket material from the local parts house.