29 replies to this topic

[flashburn]

Okay, I need to consult the gurus! All this is on a 1.6 Spec Miata engine.

 

At the end of last year, I was starting to see some oily water seepage out of the back of engine. Nothing major, but enough to keep an eye on it. I did a compression check and everything was 170-180 psi. After NCM this year, it became a considerable leak, and now I began overheating. I was also getting combustion gasses in my water, which I thought accelerated the overheating. Oddly enough, it was still registering 170-180 psi. I wasn’t getting water in my oil, but I thought I should change the head gasket anyhow.

 

I disassembled the head after NCM this year. I didn’t have the head checked by a machine shop, but I did put a straight edge on it before reassembling. It looked fine. So, I replaced the head gasket with OEM, which has fixed the combustion gasses in my water problem. However, I’m still overheating and I’m still leaking a good amount of oily water out of the back of the engine? Still not mixing water or oil in the block or the radiator which has me puzzled.  Finally, power seems a little down as well.  Yesterday I checked the water pump, it’s impeller is nice and clean and spins well. I checked the coolant flange on the back of the head, it’s still dry as a bone. Compression is now 170, 165, 170, 180 which isn’t ideal, but it’s still within the 15psi that the book recommends.

 

What do I do next? I have a spare head fresh from the machine shop that was just decked, but it’s an unknown mileage OEM valve train and my current head was built by MaCann, a NE Ohio race shop. I also have one more head gasket on hand to make the swap with.  The wild card here is we race at Mid Ohio in a week and I have limited time to "make the call" on what to do.  The car runs and drives well still, which has me totally confused. Thanks in advance!!

 

[Alberto]

I'd try a cooling system pressure tester to look for leaks.

In case you don't know what that is:

https://youtu.be/96aQ5DD5y78

[Justin Casey]

It could be as simple to trace by running it for 10 minutes with a piece of cardboard underneath to get a rough idea of where it could 

potentially be leaking. 

 

I've had issues with the engine leaking on the backside of the engine closest to the firewall, in between the thermostat, as well as the pipe

that connects to the block on the drivers side of the car. Definitely trial and error but its most likely something simple. 

 

Best of luck searching!

[Bench Racer]

Seepage from where exactly?

 

Did compression check engine normal warm?

 

Do a leak down test.

 

If you have high leakage, you should listen for air hiss in the following areas:

 

Exhaust pipe – May indicate a burnt or stuck exhaust valve

 

Carburetor/Throttle body â€“ Could indicate a bent or stuck intake valve

 

Oil filler or dip stick – Possible broken ring or piston

 

Radiator cap - Bubbles in the radiator indicates a leaking head gasket or cracked head (Doing leak down or cooling system pressure test, do it normal warm engine/hot. Doing a leak down test you'll learn more about your engine. A friend may have a leak down tester.) 

 

http://www.longacrer...ngine Leak Down

[Rob Burgoon]

Doesn't the 1.6 have that awful little rubber stopper on the back of the head near the heater hose?  That thing likes to go bad and leak if it's old.

[flashburn]

Thanks guys, I've picked up a cooling system pressure checker and a leak down tester this evening after reading a few other threads here waiting for replies!  I'll try and do those tomorrow.

 

A few things I can check off your lists:

1) I know its coming from the back of the head because of putting cardboard down and tracing up (I use cardboard for SO many things!) It's coming from below the head, above the block, somewhere near the starter.

2) Compression check was warm.

3) No bubbles in water after replacing the head gasket, but that was originally a problem.

4) Changed out radiator caps as well to make sure the system wasn't OVER pressurized. No change in leak.

5) I can verify that little rubber stopper is good, it's actually the very first thing I checked!  That whole housing is bone dry, actually.

 

The thing that really perplexes me is that it's leaking oily water, but i have no water in my oil or oil in my water anywhere else?!

[callumhay]

The water could be contaminated with oil after it comes out. There is a freeze plug on the back of the block that is very close to the trans plate and starter. That area is very oily. It's possible water may be working its way out there . On the back of the head you only have the black plug and the housing unless there is a crack in the head. Based on where you are the freeze plug would be on my list.
Cal

[flashburn]

The water could be contaminated with oil after it comes out. There is a freeze plug on the back of the block that is very close to the trans plate and starter. That area is very oily. It's possible water may be working its way out there . On the back of the head you only have the black plug and the housing unless there is a crack in the head. Based on where you are the freeze plug would be on my list.
Cal

Ah, this is what I feared, but I also couldn't find it in my Hayne's.  Do I need to pull the starter off to see it?

[luvin_the_rings]

CHECK THE RUBBER NIPPLE! A bad clamp on that or just old age wears out the rubber.  If it is bad, buy an oem one from mazda.  A normal vacuum nipple is too thin and will fail again.  The MAZDA one is like double the thickness.  

 

Squeeze the nipple or flick it to see if more water comes out when you touch it.  

 

[Steve Scheifler]

I'm pretty sure he said he already milked that idea.

[Bench Racer]

Rear of block. I believe this is a 1.8NA block. 1.6 has same freeze plug/location and same oil plug/location.

 

https://www.bing.com...x=34&ajaxhist=0

 

Side of block. Rear most freeze plug of the 4 freeze plugs could seep and travel rearward and down.

 

https://www.bing.com...ex=0&ajaxhist=0

[callumhay]

I have a picture with the flywheel on that shows the position of it. Can't upload here due to size but if you message me an e mail can send to you. I'm no expert and have only done these with the block out of the car. You will not see it if you take the starter off. I think you will need to take tranny out and look above flywheel at 12 o'clock. Taking coil pack off will help on tipping motor back to see. I think to do the job properly you need flywheel off the car as the clearance above it is very tight. No question you can see it with trans out. Would let some folks who know better correct me if I'm wrong, but water on the flywheel is likely to cause pressure plate to slip and cause u to be down on hp. Also water might be coming out at bottom of trans where bolted to engine or at boot for clutch slave/fork.

[flashburn]

Okay guys, here is the update:

 

Water pressure test, held at 16 PSI.  I did find a bad hose clamp, but it was no where near my leak down the back of the block.

Cylinder Leak Down Test - all between 10 and 15 percent.  No air out of the dipstick tube, intake, nor exhaust valves.  Is it safe to say that is "in spec" then?

I was able to see the rear most freeze plug on the side of the block which is nice and tidy.

I checked the rubber nipple again, for posterity - still dry as a bone.  Couldn't milk it if I had to - badabing.

 

I'm grasping at straws now, but I'm narrowed down to the freeze plug on the back of the block inside the transmission bell housing that last two helpers posted.  Unfortunately, I don't have the facilities to take the engine or tranny out. So... can anyone think of anything else I should try before I completely pull an engine here?!

[callumhay]

The other thing to check would be the gasket in the housing next to the black plug. Difficult to get to , probably need the coil pack removed to look at it. I don't know if it would harm anything to add some dye like food coloring or even just antifreeze to coolant, run the car until water comes out and then start disassembling what you can to get as good a look as you can before you make a decision on pulling the motor.

[flashburn]

Thanks Callumhay.  I'll try some die and see if anything shows up, up top.  Unfortunately for this problem, I did change that gasket on the housing on the back when I did the head gasket.  I wish it were just that gasket!!

[Bench Racer]

With the 10-15% leak down, are you sure the piston remained at TDC or very close to TDC? My  1.6 leak down is under 3%. I've never tested an engine at 10-15%, I would believe you would hear something. Are you sure the leak down was not coming from the leak down tester to spark plug hole? < This can be a bitchy deal to seal. I bought a steel tube extension which the tester connected to. Saul made his own connector with a modified spark plug.

 Unfortunately for this problem, I did change that gasket on the housing on the back when I did the head gasket.  

What is this "gasket on the housing" you guys speak of?

 

Have you checked leakage from the crank angle sensor sealing (the o-ring fits around the pilot diameter of the crank angle sensor) o-ring leak/seepage?

 

Put in some dye or antifreeze, get engine warm, let it leak onto something it will not soak into and taste it.

 

Do you have a small mirror on a swivel handle to stick behind the firewall and rear of engine.

 

Where are you in Ohio. Got to be a driver nearby. Two heads doing a look, talk are better than one.

[flashburn]

Hey Bench, thanks!

 

3%?  Wow, I'm sure I'm sealed and piston is at top dead center.  My leak down tester, however, is very cheap and could be at fault.  I had to get the harbor freight tool because it was all I could find same day.  I figure that if I use it as my "unit of measure" vs. a true percentage break down it would still inform me if I had a problem.

 

I did, however, run 120 PSI into each cylinder without the tester to check for leaks through the intake, exhaust, and diptsick - all were good.  No leakage anywhere, honestly probably much closer to that 3% figure.

 

I used a coolant flange gasket on the back of the head where that flange for the heater core mates to the head.  I got it OEM from MazdaRacing's program.

 

Crank Angle Sensor was a great idea!  I checked it today while fiddling with everything - however it's also bone dry

 

I don't have a mirror, but I do have visibility on all sides of the engine and I can't see anything visibily leaking.  I ordered some black light compatible dye to try, but it won't be here for several days.

[Steve Scheifler]

If the leak is behind the bellhousing you would have fluids coming out the weep hole in the bottom.

I seem to recall that the dip stick tube goes below the oil level when full, in which case you would not hear a leak there. Did you listen at the oil filler? Also, does air come out from any of the spark plug holes?

[davew]

First 10-15% leakdown is pretty bad. That pressure has to be going somewhere. Did you put you ear up against the exhaust pipe to listen for air flow? Did you remove the intake tube and listen for air flow out the intake with the butterflys held open?  Steve is correct, the dipstick will not show leakage as it is below the oil level, you must check at oil cap.

 

Your issue is with water leakage. Valves, and rings do not leak water. You need to know if you are pressurising the cooling system. Check for bubbles in the rad. And check it hot, but be carefull removing the cap when hot.

 

10-15% is a lot of leakage, it has to be going somewhere. Thus your results are non-conclusive.

 

My suggestion, have an experienced SM guy do the test to definitively show what is and is not the problem.

 

Dave

[flashburn]

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.