29 replies to this topic

[Alberto]

When you did the pressure test, how long did it hold 16 psi for?  Have you repeated the test since fixing the hose clamp and other stuff?

 

Here is a pic of the rear of the engine and head so you can see where the freeze plugs are.

https://goo.gl/photo...9j8rHsL3hxTrqQ8

 

I can't imagine a scenario where you pressure tested the cooling system and it wouldn't show a leaky freeze plug...

Besides the 'cursed rubber plug', the green sensor in the rear water housing can also leak if it's o-ring gets hard and brittle and fails.  See this pic:

https://goo.gl/photo...7rG95wMZ7x4Eg6 

 

 

How big of a leak are we talking about?  Do you have pics of the witness marks on the engine or the cardboard?  

 

You might want to pressure test your fuel system as well in case a fuel injector o-ring is leaking.  Also check your PCV.  It's unlikely to cause your issues but can't hurt.

 

 

Here is a link to my album with a ton of other engine pics from when I rebuilt my motor

https://photos.googl...JqRmzbpGbeX0jwz

[flashburn]

Thanks Alberto, that picture is brilliant!  I think my working theory is that water is weeping out the freeze plug and catching a little oil residue from the rear main, and maybe some clutch dust that's flung around in that area.  It's only doing it when the car starts to build heat, and we are talking drops - not a stream - of water.  After a track session, it will dribble about a quarter cup of water from start of the race to finish.  It will keep dripping until it gets cold, then it dries up.  I have to add about 5-10 ounces of water after a day of racing.

 

After tightening the clamps, I did a pressure test for 30-40 minutes while I fiddled with other things.  It held from 16 PSI, dropping to maybe 15 PSI over that time.  No leak.  I haven't done it warm though, I could do that tonight if you think it will warrant any new information?  Since I already know it leaks when warm, I haven't bothered to try it that way yet.

 

I have replaced a couple of injector o-rings as well.  But the fuel system is nice and bone dry now.

[Bench Racer]

 I haven't done it warm though, I could do that tonight if you think it will warrant any new information?  Since I already know it leaks when warm, I haven't bothered to try it that way yet.

Do your garage test under same conditions as race conditions. Check your temp gauge to see you have similar temperatures. let it leak on a non absorbent material. Taste the leakage.  Without a psi sensor in your water system, 8-10 ounces of leakage during a race could get worse in a hurry and could cause you engine grief you don't want. If this leakage gets really out of control during a race by time you notice your temperature gauge your water temperature could have caused havoc with your engine. 

[davew]

So a major update last night, thank you for everyone's feedback.  After reading everything, and a few PMs, here on the forums I realized I had performed the leak down test incorrectly (read the manual for the tool poorly and was inverting the order of operations).  I rechecked last night after warming everything up and my leakage was 2-5% across all cylinders.  I had a 5%, 3%, 2% and 3% across Cyl1-4.  This sounds much healthier based of what I've been reading on the forums.

 

I also revisited my compression test to double check after I re-torqued and re-assembled the head.  Still around 170 to 180 across all 4 cylinders, which seems low for a really good comp engine - but usable.

 

I also replaced my thermo switch and thermostat last night. The radiator fan is properly kicking on now.  Hopefully that addresses my heat issues.

 

So - I think that takes us back to the mystery water leak?  Please, continue to throw any other ideas at me.  I'm a firm believer in fix what you know is broken, first.  Move on to the mystery stuff last.

 

Remember a 1.6 has 3 temp sensors

 

front, round connector,on top of thermostat turns on rad fan

rear, green Bosch style connector, on heater hose housing is temp sensor for ECU. Acts as the choke mechanism

rear, pass side of cylinder head, under intake, very hard to find, single spade wire, works the oem temp gauge.

[davew]

So a major update last night, thank you for everyone's feedback.  After reading everything, and a few PMs, here on the forums I realized I had performed the leak down test incorrectly (read the manual for the tool poorly and was inverting the order of operations).  I rechecked last night after warming everything up and my leakage was 2-5% across all cylinders.  I had a 5%, 3%, 2% and 3% across Cyl1-4.  This sounds much healthier based of what I've been reading on the forums.

 

I also revisited my compression test to double check after I re-torqued and re-assembled the head.  Still around 170 to 180 across all 4 cylinders, which seems low for a really good comp engine - but usable.

 

I also replaced my thermo switch and thermostat last night. The radiator fan is properly kicking on now.  Hopefully that addresses my heat issues.

 

So - I think that takes us back to the mystery water leak?  Please, continue to throw any other ideas at me.  I'm a firm believer in fix what you know is broken, first.  Move on to the mystery stuff last.

 

Remember a 1.6 has 3 temp sensors

 

front, round connector,on top of thermostat turns on rad fan

rear, green Bosch style connector, on heater hose housing is temp sensor for ECU. Acts as the choke mechanism

rear, pass side of cylinder head, under intake, very hard to find, single spade wire, works the oem temp gauge.

[Steve Scheifler]

Check hot. Things expand as they heat, tiny cracks get bigger, different things expand at different rates and produce gaps for leaks to show themselves.

Perhaps I missed it up above somewhere but I will repeat, if the leak is behind the engine enclosed by the bell housing, as with the rear freeze plug, it will be obvious at the transmission weep hole. Is anything running out of that? If not, look elsewhere.

[flashburn]

After having some PMs from you guys about low compression figures and being significantly down on power at Mid Ohio, I decided to buy the tools to fix this myself.  I've pulled the engine and put it on a stand so I can re-ring it.  The freeze plug on the back of the head looks fine, but I'll have to pressurize the system prior to putting it back in the car but after I can rebuild everything.  I've uploaded a bunch of photos that I took of the condition of the engine.  I welcome any feedback you may have as I order up some parts from Mazdaspeed.

 

I checked all the cylinders for warping/ovaling, and everything was pleasantly round still. Each cylinder was between 77.88 and 77.92.

 

Here is a link to all the photos: https://goo.gl/photo...jbAwL5iTTKRLqX6

 

The shopping list to date:

Rear Main

Alignment shim from block to head

Pilot bearing

head gasket kit

rear freeze plug

 

Got any recommendations for:

Piston Rings

Clutch disc

[Alberto]

After having some PMs from you guys about low compression figures and being significantly down on power at Mid Ohio, I decided to buy the tools to fix this myself.  I've pulled the engine and put it on a stand so I can re-ring it.  The freeze plug on the back of the head looks fine, but I'll have to pressurize the system prior to putting it back in the car but after I can rebuild everything.  I've uploaded a bunch of photos that I took of the condition of the engine.  I welcome any feedback you may have as I order up some parts from Mazdaspeed.

 

I checked all the cylinders for warping/ovaling, and everything was pleasantly round still. Each cylinder was between 77.88 and 77.92.

 

Here is a link to all the photos: https://goo.gl/photo...jbAwL5iTTKRLqX6

 

The shopping list to date:

Rear Main

Alignment shim from block to head

Pilot bearing

head gasket kit

rear freeze plug

 

Got any recommendations for:

Piston Rings

Clutch disc

 

FYI - Mazda Motorsports had some kind of special deal on an engine gasket kit that included the valve stem seals in case you need them.

I got my piston rings from Mazda Motorsports.

For clutch disk - ACT 4 puck sprung would be my suggestions.  The springs should relieve some of the shock from shifting adding life to the trans.  At least that is what old threads on the topic suggest...

Here is a link to my blog with my experiences rebuilding my 1.6 - including piston ring alignment where the FSM I was using was not accurate.

http://blog.miataracer.com/

Hope that helps.

[flashburn]

That was a great read, thank you! I will go grab those brushes as I definitely struggled with cleaning everything when I did the head gasket.  After reading that all, it sounds like I'm on the right track for my parts bin list.

 

EDIT: For anyone who might search for this later, as per the repair manual: Measure the piston 90 degrees perpendicular to the wrist pin, at the base of the pin.

[flashburn]

Finished doing my rebuild, thanks for all the help.  The engine goes in tonight (hopefully)!

 

For whatever it's worth, the water leak was indeed the freeze plug on the back of the bloack.  The hole in the block had some imperfections which I spent the entire day yesterday correcting.  It took me several tries at hammering in the replacement freeze plug (5 plugs later, success).  I added a small amount of blue loctite to seal the filing gaps.  For anyone that might be tackling this, my advice is to buy more than one freeze plug as they have to go in perfectly straight the first time!

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