Mazda Rotary Club

I only ask because since my car had new intercooler and filters the other day we then dynoed it at WGT.

Whilst on the Dyno it ran real lean just before redline due to boost creep and cut.

The compression is fine, minimum reading was 8.2. However since that day I have not had a steady water level and after parking up today I came back to the car 30 mins later only to see water ****ing from the expansion bottle.

Fired it up and took the water cap off (main not AST) abd it slowly slowly started to rise until it was overflowing. Although no champagne bubbles.


Anyhow I digress. simple question, could detonation blow a water seal?

I would not have thought so, as the seals are on the ends, not were you would expect detonation to occure, there is a small risk I guess that if a piece of apexi seal came off it could damage a seal while going through the engine cycle, but I would have thought unlikely. But I am Far from being an expert.

apex seals are fine mate.

Its just a wierd one because I had the whole water system pressure tested when I got a new rad about a month ago and the water seals are less than 2 years old. However I am definitely losing coolant and wherever its going is invisible.

It is possible you have a cracked plate,where the water seal sits.Detonation could do this.

QuoteOriginally posted by Timrxmotors
It is possible you have a cracked plate,where the water seal sits.Detonation could do this.

great  :rolleyes:

Tim mate,


would that show in a compression test?

It wouldn\'t show in a compression test.
Tim maybe right,or it just maybe that a water seal has let go any way or even a side plate has corroded.
Regards
Carl

man if it is an internal engine problem I\'m gonna be so gutted. had it up to almost 320 at the wheels, great compression, loads of new shinies.

Please be something simple.......


time to find religion I think.

You could try a coolant system pressure check,that ought to give a good indication if anything is wrong.
Sometimes the fix can be as simple as changing the pressure cap on the AST tank.
Make sure it is a 0.9kg one or 13lb.
Regards
Carl

Don\'t think so. If your motor had started detonating, it would have killed the apex seals. It only takes one or two good pops to crack a seal. What normally does the water seals is if the engine overheats or develops hot spots due to localised boiling of the coolant. This causes the rotor housings and end plates to warp, exposing the seals directly to the combustion gasses, needless to say theyt don\'t hold up long! Has your car been cooked recently? Either that or end plates/rotor housings have sufferd from corrosion like carl says. Anyways, if your water seals had gone you\'d defo see bubbles of combustion gasses rising to the surface in the filler neck. If you run her with the filler cap off, the coolant will rise due to the fact that it expands as it heats up, no problems there. Coolant can only get to the overflow tank via the AST cap, take it off and inspect the spring. Might have gotten a bit tired. Also check that the little return valve opens properly. Without that, your overflow bottle level will get higher and higher because the coolant isn\'t being drawn back into the engine as it cools.

cheer MillSpeed mate, appreciate that. It didn\'t seem to make sense to me that it could have popped a water seal but hey, thought I\'d better check. It\'s definitely not cooked at all and having had a rebuild pretty recently I am also dubious about it being corosion. I did pop the AST cap off and have a look at it straight away and it looked fine, rubber seal fine spring looked ok etc. Still it is a 13 year old cap now, I\'ll go get a new one from Halfrauds and see if it makes any odds.

Yeah, it\'ll only be about 4 or 5 spods, better than paying £18 from mazda! Well worth chaging these little buggers pretty regularly......they do let the coolant pressure drop over time, letting the boiling point of your coolant fall dangerously close to the engine\'s operating temp.

Well, I think detonation could damage a water seal. The water is seal is exposed to cumbustion pressure, right?

Now, when we have detonation, we have an uncontrolled explosion, and to me that means that :
1) surely the pressure could rise higher than it would in a normal firing event.
2) the pressure could be applied in the wrong place - to places on the water seals that are not normally exposed to combustion pressure.

Please tell me if I talk bollocks ( mind you people DO on this site anyway!)  :D :D

Buy a genuine Mazda pressure cap,the ones from the factors never work the same.
Regards
Carl

QuoteOriginally posted by Martiny
The water is seal is exposed to cumbustion pressure, right?

Hells No! Well, not unless the rotor housings/end plates are warped. The water seals are just like giant rubber o-rings which rest in grooves machined into the rotor housings (or the end plates in early engines). If they are exposed to combustion gasses (which are at extremely high pressures) they\'ll burn through in no time.

QuoteOriginally posted by MillSpeed
Hells No! Well, not unless the rotor housings/end plates are warped. The water seals are just like giant rubber o-rings which rest in grooves machined into the rotor housings (or the end plates in early engines). If they are exposed to combustion gasses (which are at extremely high pressures) they\'ll burn through in no time.

All right.

So, when the seal fails, what is it that causes the water to pump out the expansion tank, then?

and

If your combustion chamber is as tightly sealed as you suggest, then what do we need an O-ring for?

surely if the are at the tops and bottoms they are only on the intake/exhaust part of the cycle, rather than the combustion section.

QuoteOriginally posted by Oedipus Rex
surely if the are at the tops and bottoms they are only on the intake/exhaust part of the cycle, rather than the combustion section.

Nope, they go right around the housing.

Usually, water gets chucked out of the expansion tank when the little return valve on the AST cap gets stuck shut. When the engine cools and the coolant contracts, the engine cannot draw coolant back out of the expansion tank. If you keep adding coolant to the engine, eventually the expansion tank will overflow. Alternatively, the AST cap spring might have become weakened with age, letting coolant flow to the expansion tank before it\'s built up any sort of pressure in the cooling system.
When you get warpage/water seal failure, it\'s very similar to head gasket failure on a piston engine. The increasing coolant system presure overwhelms the AST cap and some coolant gets forced into the expansion tank.
The O-rings are there (I assume) to keep the coolant from seeping into the rotor housings. You\'d be surprised the sort of gaps water can get through via capilarity!

Martin could well be right I think. But there would possibly be a mixture of oil/fuel etc. in the coolant if this happens.

Combustion is not only sealed by the Apex seals, it is sealed by Apex Seals, Corner Seals, Side Seals (all aided by the springs), rotor face, rotor housing face, end/centre plates (and the way it is all bolted together).

Generally the weak points are the Apex seals, Corner seals, (sometimes side seals), and the side housings.  This is where good apex seals and dowelling in an engine all helps.  Even if you do all of this, it doesn\'t mean you can get away with much detonation!!!  but it may be a little more tolerant.

Be interested to see if Carl, Tim have further comments on the weak points from the combustion point of view in the engine.

I think have the pressure checked - should hopefully provide a few more clues.

Oedipus Rex - I was actually going to ask how many miles were on it, but you said it had been rebuilt recently, so it shouldn\'t be corrosion.

Also - with extreme detonation the plates/housings can literally seperate themselves. Hence the mixture of oil/water in either and/or the cooling system (both oil and water), and coolant in the combustion chamber --> leading to loss of coolant.

This is why I think Martin\'s point is quite valid.

& for the more simple among us: boom boom is bad? lol
Si

QuoteHells No! Well, not unless the rotor housings/end plates are warped. The water seals are just like giant rubber o-rings which rest in grooves machined into the rotor housings (or the end plates in early engines). If they are exposed to combustion gasses (which are at extremely high pressures) they\'ll burn through in no time.

slightly confused i think!   very early models had the O ring grooves in the rotor housing,  for the last 20 years or so the grooves have been in the end and centre plates except for the Renesis RX8 which are back in the rotor housing!   I wish they would make up their mind  :confused:

Like any gasget,  if it was exposed to the full pressure of combustion it wouldnt last long but because the o rings are in grooves the are protected and only have to seal the tiny gaps that two metal surfaces mating leave, but still take a bit of flack which is why you can pressure the water system if its knackered.  The combustion o ring is teflon coated and is quite tuff, (try scraping an old one out of its groove!

Of course i may be wrong:(

Why not just pull a spark plug to check for signs of water contamination? If none, then that\'s not your problem.

May be hard to tell from the Spark Plug, it would be more obvious from lots of WHITE exhaust smoke, or coolant in the oil, or oil in the coolant.

It could still be something silly in the coolant sytem!  I\'m sure we\'ll find out soon.

bloody FD\'s and there coolant system, a royal pain in the arse.

Got a new AST cap today but I reckon I\'ve sussed it anyhow. After going out for a proper spin tonight I parked her up and still had the light on. Noticed a load (well some) of steam coming up under the passenger headlight. Gonna jack her up tomorrow and see if a hose has come loose from the rad somewhere.

QuoteOriginally posted by antnicuk
slightly confused i think!  

Ah, my mistake. The water seals moved to the side plates on the post \'86 13B\'s. I wonder if there was any particular reason for Mazda moving them back in the Renesis?

QuoteOriginally posted by MillSpeed
Ah, my mistake. The water seals moved to the side plates on the post \'86 13B\'s. I wonder if there was any particular reason for Mazda moving them back in the Renesis?

My money would be on an engineering compromise.  

Probably sealing in the side plates have some drawbacks (like metal thinness amybe) but sealing in the other position places them in a hotter position (just a guess that the turbo\'d engines run hotter...).

Thinking about it though, if the detonation had been severe enough to separate the rotor housing from the side plate, then wouldn\'t the symptoms would be alot more pronounced than an overflowing expansion tank? I mean surely apex/corner/side seals would\'ve been severely damaged (or even spat out!) leading to, at the very least, the car running like ass.

Yep....

QuoteAlso - with extreme detonation the plates/housings can literally seperate themselves. Hence the mixture of oil/water in either and/or the cooling system (both oil and water), and coolant in the combustion chamber --> leading to loss of coolant

QuoteOriginally posted by antnicuk
only have to seal the tiny gaps that two metal surfaces mating leave, but still take a bit of flack which is why you can pressure the water system if its knackered.  

Well thats what I meant.

Between the water passage and the combustion chamber we have only this water seal. Yes there should be a good seal fomred by the side and rotor housing, and this seal will only be exposed in very very tiny places. But I still think it could be damaged by extremely high pressure.

What a good discussion so far!:D :D

Ah ok, I got you now. I didn\'t realise the seals were exposed anywhere under normal operating conditions. I suppose that\'s why the yanks are experimenting with all kinds of strange materials for the water seals. Weren\'t Rotary Aviation offering some kind of uprated water seals?

Here\'s some interesting stuff:
 
http://www.hayesrotary.com/page11.htm

Looks like the stock seals are just rubber. A few companies are offering these up-rated teflon relacements. Notice the stainless steel seal protectors, I wonder if they\'re any good?

Cracking thread on the subject here:

http://www.rx7club.com/showthread.php?t=130983&page=2&pp=10&highlight=teflon+seals

QuoteOriginally posted by MillSpeed
Here\'s some interesting stuff:
 
http://www.hayesrotary.com/page11.htm

Looks like the stock seals are just rubber. A few companies are offering these up-rated teflon relacements. Notice the stainless steel seal protectors, I wonder if they\'re any good?

Cracking thread on the subject here:

http://www.rx7club.com/showthread.php?t=130983&page=2&pp=10&highlight=teflon+seals

The Mazda seals also come with the steel inserts. Well, they did on all the times I\'ve rebuilt engines. I think the Hayes ones might be better being stainless steel.