OK- Background-

89-91 wiring/ecu/engine in '87 chassis. Total hodgepodge. Also VERY ugly.



Goal to make it as hideous as possible, so that the only thing I care about is having fun- no interior/exterior worries to add to things, just strictly get in and GO. Received as an empty shell and built myself. Now onto the problem

I've put around 1300 miles on since getting it put together. The engine was an unknown S5 NA that I got on CL for $150 since it wouldn't start (bought the fuel tank from the guy too, bad gas was the cause of the no start). Put it in the car, and until now, it was totally fine- Overflow bottle always stayed at the "FULL" Line, or below when cool.

Now however, I noticed after a 45 mile trip that the overflow tank is nearly overflowing, and a stream of bubbles (not champagne but more like the "bubble density" of blowing thru a straw in a cup) is coming up.

Surest way to tell would be to purchase a hydrocarbon sniffer, just un-sure where I could find one of those, but I'm thinking it's a bad coolant seal. I'm just shocked that I did the first 1300 or so miles and didn't experience any problems!

More on the cooling system:

-S5 gauge, never past the "normal" 1/2way mark,
-under belly pan is there,
-new copper rad, but lower hose attachment port is hammered in some to clear a speedway sway bar (CRINGE I KNOW!!!),
-has thermostat that came in engine when purchased,
-Engine is an S5 factory reman build date XX/1998, with ~50k miles (based on what I was told and overall engine condition, looking in ports, etc)
-brand new coolant, did a flush of block when i had it on the stand and coolant was nice and green & came clear quickly.
-Did fling an Alternator belt & was un-aware, with nothing left driving the WP. Traveled home about 9 miles, and then realized after about 5 miles the next day on way to work, and put a spare on I had in the hatch. Neither time did the gauge come over 1/2.
-Stock clutch fan, stock fan shroud.
-Overflowing/bubbling of bottle didn't start until LAST NIGHT after said 45 mile each way trip, which was done w/o a hood as I was on the way to purchase another, and don't have a truck.
-PER an infared thermometer, no point on the engine is ever over 180*F, measured at idle
-Rad cap was a .9bar, replaced w/ 1.1bar, bubbling still persists.
-NO signs of vac leak between overflow bottle & rad (IE, overflow line)

Anyway, per searching, no one had a situation JUST like mine, so just trying to get some other experts to chime in... or something.

Worst case I pull the thing & do a "budget" rebuild just cleaning everything and only do a gasket kit, as w/ the condition of the engine, most everything ought to spec out.

Thanks guys!

 

a. that is your truck.

b. i would inspect the surface the radiator cap(s?) seal on, i've seen that be full of crud, and it will cause the symptom you describe, as will a bad radiator cap.

c. the S5 gauge has a centering thing, so its kind of useless for stuff like this. i would check/replace the thermostat. if you check it, the spec in the FSM is the MINIMUM opening, a new thermostat will open almost twice that.

 

Tried cleaning the cap and its seat on the rad, get home and rev in neutral while watching the overflow.... BUBBLES GALORE!

atkins kit ordered, since I feel pretty firm w the internals of the motor I'm only doing orings. Role model budget build haha. Will post carnage pics as I open it! I've got a goal of having it ready to drive to work monday, 6 days from now. Fun weekend! Haha

 

sounds like a bad coolant seal if it persists through a 1.1bar cap and the seat is clean.

being a '98 reman it would probably still have 3 piece apex seals(in fact i don't think they made 2 piece OEM seals until '03 and an OE reman will have OE seals), i highly recommend replacing them with new 2 piece seals.

 

probably a pinhole leak if its not overheating but it will get worse eventually.

Rotary > Pistons

 

Rotaryevolution- thanks. Why do you/most think its not wise to reuse the 3 piece seals? Persuade me to make another $200 order lmao

 

i think that's correct, 2 piece seals didn't exist until sometime in 2003, maybe 2004

i'd measure the 3 piece seals, they do 200k all the time

 

i've just seen odd combinations of reused 3 piece seals that walked off the rotors. to me it's not worth the risk of prematurely losing a rotor and housing when the 2 piece seals can go a bit further.

i would venture to say that a good 2 piece seal will far outlast even the 3 piece seals that went 150-200k+. they also have less tendency to carbon stick to the rotors and cause the infamous 0 compression issues you run into further down the line.

 

That's actually how my motor died the first time. Coolant seal blew out on the exhaust side so it'd run just fine but blow exhaust into the coolant and flood one rotor with coolant if i let it sit for a couple days.

You could pressure test it and see where it leaks?

 

Get Irontite -- the red bottle.

 

Engine is out! Will have her cracked open probably by saturday. I'm thinking the iron failed. Well see!

Also pending seal condition I'm going to re use the apex seals. The 200k ref did me in haha.

 

You can get a head gasket tester kit at napa for $40
It should last years of testing coolant seal failures
Has the glass beaker and bottle of chemical dye

 

Oh and just so ya know I seized an engine on 3 piece seals
Top half got too thin and rolled out of the apex seal slot
Trashed the rotor and housing without actually breaking the seal
RA classics are cheap, but don't use they're springs, use oem
The RA springs were not consistent bends at all and had sharp ends

 

Check it!!



That's the center iron, on the front rotor side.



Bottom right section of it.

Here's another question:

I've got 1 spare S5 center plate, but it's from an engine that my girlfriend (LOL seriously) pulled from our local junkyard. It's also a mazda reman & looks good. I'd like to keep it with the rest of its parts so I have a matched set. So onto the question:

I can use an S4 center iron, correct? Obviously block off the EGR valve, and the EGR port below the 2 primary intakes is missing, but all of my emissions are blocked off anyway, so that shouldn't be an issue... Yes or No haha

Other than that I'm ready to start the rebuild process. I'm going to lazy-lap the plates w/ an orbital sander (have seen good results this way!) I'd like to cut out the exhaust diffusers too, but... it looks like a lot more trouble than it's worth. Also need to spec the seal heights and such just to be sure.

Here's another observation- this engine had FD corner seal springs. Did all Mazda builds use those after '93?

Thanks all!! Enjoy the carnage pics!

 

Nice progress, I want to learn to rebuild one of these bad boys if I can get a spare car as a project to keep learning more.

Is this your first rebuild or have you done a few before?

Rotary > Pistons

 

2nd rebuild, 4th if you count the 2 sachs air cooled single rotaries I did haha. Also have disassembled maybe 25 or so in junkyards on the hunt for good spare parts.

Definitely recommend giving it a try. Its a lot to learn but challenging and rewardimg.

 

Would've gotten further this weekend but decided to purchase this thing



It's a '9/78 build SA, hood prop is on the pass side too & has the wonky perf'd dash. Through a chain of trading events I essentially paid $9 for it. (Holley FPR, pump, & carb which I had $0 into, plus 2 FC door handles, the $9 parts, I traded for a microtech LT8 & harness. Then proceeded to trad that for the car. Excited!!)

 

Dude your fc looks so shitty I almost like it.
The vert wheels are a nice touch

 

Time to update your signature. All 20 cars are not there.

 

Update! Approx 1500 miles since rebuild. No oil leaks outside, coolant level maintains full (ie no maintenance)

I reused the rotors, housings shaft and front iron. Center and rear came from a set of parts I just picked up.3pc apex seals were on the low end of dimension spec, but going thru my pile of spares I found some that were high side! Used sprigngs everywhere, corener seals found w min wear, other side seals tested to find some w .003" clearance. Helps having lots of spare stuff and always taking the seals from a junkyard engine upon disassembly lol. Atkins oring set and a new front cover gasket is all I have $ wise into the build, and my time. Remlved exhast diffusers (cut out, sleeve still in place), hand lapped irons w vavle grinding compound, initially breaking glaze w an orbital sander and 120 grit wet. Scuffed housings w emery cloth. No omp running 2 stroke, atkins sleeves.

Compression #s!! Remember this was a BUDGET rebuild an only my 2nd one. W mazda comp tester- 7.2 6.8 6.8 @245 front, 7.4 7.2 7.2 @ 247 rear. Yea! Happily back on the streets again offending people w its ugliness lol