This is a bit of a duplicate post from my last entry under the "anyone with epoxy experience". I felt as if there was enough new information that I should re-examine whether there really is a hole in the primary runner.



I've been cleaning the offending part with acetone and for the life of me, I can't see how this thing is causing a coolant leak. There's no visible hole, light doesn't shine through it, and acetone pooled around the spot in question does not leak through.



So the facts are:

1) car burns coolant but only seems to do so under boost conditions above .75kg/cm2

2) car does not seem to burn coolant under .7kg/cm2 or under vacuum conditions

3) coolant residue was found in the uderside of the oil filler cap

4) if I boost above .75kg/cm2 and the engine "swallows" a bit of coolant, I can rev it, drive around a bit and the coolant will clean out and the car operates normally. 100% normal under vacuum conditions. Vacuum levels are just fine, about 375mm to 410mm at 1100 rpm

4) there seems to be a pitted spot in the front rotor's primary intake runner

5) we can press on it with force and it does not open up or give way



After I cleaned it, I had the idea of sealing off the ports. They did this at the shop too, using hands to block off the ports and using compressed air. A thin sheet of paper, stuck in the coolant passage below the port fluttered when air was applied to the port.



I decided to duplicate that experiment but I used thin latex gloves and towels to seal the ports. The soft latex provided a good seal. I also plugged the small port inside the injector bung and proceeded to blow as hard as I could (no jokes please) into the top of the injector port. Enough force was applied that eventually the glove/towel combo was pushed out. No air seemed to leak into the coolant passage.



Since it only leaks when boost is applied, I would think that the coolant would leak under vacuum conditions as well as under boost. The coolant system is under far greater pressure, 16psi to be exact, so theory holds it would leak all the time, no?



I'm about ready to run back over to Walmart and purchase a bit of playdough to really seal everything off but I'm almost ready to bet my left nut the "pit" in question is not causing the leak. I'm footing the bill for the whole fiasco since the shop has determined that my port job was responsible for the coolant leak. I'm now wondering if it's a convenient scapegoat for not assembling/checking the engine properly.



Where are common areas that leak coolant? Besides problems with porting, afik, they can leak around the spark plug area. We tested that. Nothing. Now, if the plates weren't checked for flatness and there was one small area which was uneven, higher boost levels would expose this weakness wouldn't it? If the bolts weren't tensioned properly, unevenly or too tight, problems could be created, correct?



Thing is, if the engine were expanding laterally, it seems like oil/coolant would leak OUTSIDE the motor as well, not just inside.

rear rotor primary runner. Same circular plug at the bottom of the runner, again, looking through the primary injector hole.

interesting........i think i remember hearing about this problem from pepe loco..... something about the casting style on original cosmo plates.... he used all new stuff on his 20B

Any evidence of seepage past coolant O rings? Since the condition is boost sensitive, I would suspect something in the intake system like any warm up devices with coolant hoses leading to them. Although, since coolant is under the oil fill cap, coolant is also in the engine oiling system. So where could the oiling system and water jacket interact? Maybe a cracked coolant passage in an endplate that is alongside an oil passage?

It'd have to be a spot that allows coolant into the combustion chamber too. I didn't see any evidence of seepage. We used stock Mazda o-rings and they come apart when pulling the engine apart. I'm not enough of an expert to tell however. I didn't see any evidence of pinching or a broken seal.

https://www.nopistons.com/forums/pub...1047683561.gif https://www.nopistons.com/forums/pub...1047683561.gif It is weird that is only leak on boost, it should leak all the time. I take it you didn't do the coolant pressure test before you tore the motor down.

To me it seems that one of the plates is warped, did you reuse the old plates? But then it would leak all the time WTF https://www.nopistons.com/forums/pub...1047683561.gif

those patterns are normal on the castings, you definitely do not have a hole there in the port runner, but you could improve that porting a slight bit. Nice pics BTW.



I suspect O ring failure, triple check that possibility, make sure the groove is intact that supports the O rings, the back side in some areas gets thin and can break.



If you can rule out O ring failure, check the housings for cracks, and especially important check the freeze plugs for problems. It's really the only other place the coolant/oil can interact.

forgot to mention, I have pretty much all emissions devices removed, everything under the UIM. No coolant lines to the throttle body either.

Digital Nikon D1H and a 60mm macro w/ off camera flash cord comes in handy sometimes :-) I put a smooth layer of epoxy over the pitted area. We'll see how it looks in the morning. If it looks like crap, I'll sand/port it out.



I'll double check the rest of the plates. Thanks for the head's up pengaru.

Ok, I checked the intermediate plate again around the 0-ring groove for anything abnormal. Again, when the pulled the motor apart, the 0-rings seemed to be intact but they came apart (as I was told they should) when we pulled the plates off the housings.



What I noticed after the inspection was a bit of carbon deposited IN the rotor groove (circled in red) and a bit more black discoloration just south of that region on the face of the plate (yellow arrow). They cleaned everything within a day or two as well so if there was any other evidence, it was washed away. Dunno. Does the black just inside the 0-ring groove signal failure on the 0-ring's part?

Todd, did not do a coolant system pressure check as I do not have an AST and eliminated it with the 1st gen radiator cap. Thus their pressure tester did not interface properly.

I'm gonna guess that somehow the coolant is seaping through the pores of the metal. Under boost it get sforced through tiny holes that would other wise not be seen.

I would guess that it is a problem taht would have gotten worse until the casting actually gave way and broke off.

Looks like you just hit the lottery on shitty cast plates Michel.

Too bad I was hoping to see engine bay pics.

Get a new plate and get on with the install.

Dave

that is weird....

The wall between the coolant seals and the water jacket all in good shape. I am not sure what the width should be, but I know that when it gets to small it can collapes causing the seal to fail.



I don't think the water is going though the plate when pressurized, or it would do it with the pressure from the cooling system.



If I was you I would just stop messing with this hidden crack/leak and just spend the money and get a new housing and be done with it. You may never find what the hell is wrong and you will mostly likely have to replace it anyway.



My 2 cents

If the teflon seperated from the inner O ring and was pinched it will cause a coolant leak under the same conditions you are talking about. I did this to my last motor and if I drove the car around with no boost I wouldn't loose coolant, but If I boosted it, it would loose coolant. It was not as bad as yours, but was enough that when I let it sit for 2 weeks with no turbo on it, the corner seals rusted causing lost compression. On tear down I found an inner O ring with about a 3mm section of the teflon that was pinched between the plates.

So it could be as simple as a coolant O rings change IGY? Would the coolant pressure be enought to push though the slit in the seal?

Igy,

So you're saying that during assembly, a ring can get pinched, causing the teflon to separate and ONLY the teflon gets stuck in the wrong spot causing the leak? Or does the pinch cause the teflon to separate and that in itself will cause the leak under boost? My rings did have the teflon separated from the rest of the 0-ring but I was told that is normal upon disassembly. Is this correct? They have the reuseable kind of 0-ring that they say everyone is moving towards now (in the racing community). It's a bit thicker than the standard 0-ring and it's cross section is round as well. All black. Anyone else hear/use them?

Michel

It is normal for the teflon to seperate. Yes, only the teflon was pinched, nothing was wrong with the rubber.

if you look at the pictures of his port runners, they are barely ported in that area at all, you can still see the small circular land which is present in the stock casting and the 'pores' are actually just the rough cast _original_ surface, it wasnt even ported down enough to remove it. The problem I'm positive is not in the metal photographed on the ports.



I'm still thinking O ring failure or freeze plugs, but if coolant was getting combusted it would be difficult for the freeze plugs to cause this. The only way I can imagine freeze plugs causing combustion of coolant, is if the coolant gets into the oil and eventually supplied to the metering oil pump, and consequently injected for combustion as if it were oil.

Your parts look good

have confidence in you self

just take you time and all should be well.

remember ..... vasoline is you best friend when putting it back together

LOL, you got that right Chase! And Pengaru, you're right...I barely touched the primary ports. Just did a bit of cleaning on them and opened up the face ever so slightly. Did all the major work on the secondary side. I figured the Cosmo primaries were fine as is, and being larger than the FD's ports, I left them alone for good idle/low/midrange and decent gas mileage. I pulled about 24mpg driving across Florida some time back (not much boost). We'll re-assemble with the new o-rings today. Thanks to everyone for the input!

Just a little update, the shop said they didn't see any 0-ring damage at all and since these things come apart when opening up the engine, I couldn't tell either. But we've both agreed that it's no longer leaking from that intake port. They were planning on going over everything with a fine tooth comb and assembling the engine today. I haven't heard anything "bad" from them so I'm assuming everything checked out. We're reusing everything except for the rear rotor bearing and everything looked just fine aside from the leaking coolant. :-)



I still believe it was an o-ring issue. It's hard for me to say if the rings were damaged however. They're going to re-assemble the engine on their bill not mine so that's a plus. It really bothers me (and them) that there's no definite smoking gun/evidence as to why it was leaking. Guess we'll see. Another bonus is that it gave me a chance to do a custom install of a 25 row Mocal on the passenger's side. I managed to mount it within 1/8" of the oil cooler vent opening and position it so that the entire duct and the slot below (FEED II front end) is filled with the oil cooler. Essentially the entire cooler is getting a direct shot of air without the use of an extra duct. I also managed to do a bunch of little stuff to improve the long-term reliability of various components.

Good luck and tell us how it went!



I'll be praying to the epitrochoidal master for you...https://www.nopistons.com/forums/pub...1047683894.gif

One thing we didn't think about (but Nick at N-Tech Engineering did) was measuring the housings. Apparently they can shrink around the spark plug area due to extreme heat/cycling. No word on what my "numbers" were but the plates checked out ok (no leak either, imagine that!).

Michel

Well we're going to replace the rotor housings front and rear. They say they're in spec, but for the life of me we can't figure out where else they'd be leaking. So two new rotor housings overnight air. The apex seals, solid side seals already have 3K on them. Think they'll be ok?

Plans changing...with new housings costing a minimum of $525 EACH, we're taking some additional steps to test the engine. We're using new, reuseable 0-rings which many shops are now turning to including Pineapple. The engine will be assembled tomorrow w/o e-shaft and rotors and the cooling system will be pressurized to 40psi. A Jaytech adapter will be put on the front plate and sealed off on one side and pressure introduced on the other. Pineapple pressure tests all their motors overnight before being sent out. IF there is some sort of leak, the entire unit will be placed in water to see which housing is leaking. If nothing leaks, it was an 0-ring issue and the engien will be reassembled.

i have seen the engines leak from where the spark plugs pass thru the water jacket, its mostly on older engines, i think they have fixed the casting, but its possible



mike

Interesting. I guess this will eliminate the posibility of an o-ring not seating due to warped housings

We did check the spark plug holes for leakage. Nada. Checked the plates as well.



Are you being sarcastic Silver? I'd think it would show just that if a housing were warped.

Vasoline really shouldn't be used for coolant O-rings on assy. Use Hylomar, & use teflon ecapulated silicone O-rings for the inner coolant seal (which it sounds you already have).



Vasoline will make the O-rings swell so if you have to stop for whatever reason the O-rings are gone. If you go too slow & don't notice the O-rings swelling you can get them pinched...



The Hylomar will hold the O-rings in place much better. Good luck with things this time around.

Found the problem. We assembled the engine minus the internals and pressurized the coolant system. Hole in the rear secondary runner. I'm not a happy camper. Next time, leaving the porting to the experts or just ordering a motor from Pineapple. Sealing her up now with epoxy. Seems that the boost would "push" the crack up a bit and allow coolant to enter. It'll seal back up if you don't probe it with a screwdriver...pretty small too. Couldn't feel it at all.



I'll mention the vasoline thing to them. They're using these black reuseable o-rings. Apparently Pineapple uses the same brand. Not sure if they're teflon encased or what. What do you recommend for the outer ring? OEM?

That sucks! Sorry to hear about it.



I use OEM for the outter, & that should be fine since it's never subjected to combustion gasses. I use Hylomar to keep it in place as well. The only thing I used Vasoline for was all of the friction surfaces. I just used fresh oil on all of the O-rings & seals.



I got the teflon encapsulated silicone from mcmaster.com.

McmasterCarr O-rings, Stock outer Seals, Hylomar on ALL seals

Not sure where they get theirs but they're supposedly the same as what Pineapple uses. Anyway, they've never had a problem with seals expanding due to Vasoline and most people use just that to assemble them. I dunno. I'd definitely prefer Hylomar but I'm second guessing them often at this point. If they had just pressure checked the engine THE FIRST TIME before installing it, we wouldn't be having this discussion and I'd be about $1K richer. Just really sucks. Yes, the porting thing was my fault but each and every engine they build should be checked before being dropped into a car. I personally didn't know any better. But that's why I pay them to install it, right?



I managed to get three layers of ResinLab epoxy on both secondary ports (just in case). I did a majority of the coating on the coolant passage side. Let each dry w/help from a heat lamp. Once dried, I slapped another layer on. Should hold Hoover Dam quantities of whater https://www.nopistons.com/forums/pub...1047683358.gif

its be tempted to put a thin layer of epoxy on all of the port runners, just in case



mike

That's EXACTLY what I did. Both secondaries on the OUTSIDE and the primaries on the inside since it's difficult to get to the back side. I put three layers of epoxy on the secondaries. Let each layer dry, heat lamp assisted, then a new layer. Should deflect bullets now. This epoxy stuff is as solid as a brick wall https://www.nopistons.com/forums/pub...1047683358.gif and makes JB Weld look like playdough. Engine is pretty much assembled and will be in the car on Tuesday. Pressure testing it over the weekend.

I mis-read your post. Check to make sure the housings aren't warped. A indication of this is the dowel pins being stuckin the housing when you dissasemble the motor. Glad you found the problem. Guess you ported too far.