Hi guys,

i'm sorry for not searching it first....but my engine is being disassembled... in my mechanic's place.

my symtom was... loosing water... initially i thought that it was typical O ring failure. i was using the RA O rings, well known for fitment problem. my mechanic realise i got another problem other than loosing water, the water pressure is too great. so great that my radiator hose are expanding and it became so hard that fingers can't press it.

so.. my engine was taken out, no leakage on radiator, no leakages on any other places... but the rate of filling water is one bottle of 700 ML per day... pretty drastic.. i don't have any problem starting the car in the morning.

the engine was opened up... the good and bad news is, didn't see any sign of water entering the combustion chamber. and i ask the mechanic, what cause the water loosing.... his answer... don't know ...

my question will be,

1) will it be caused by crack on the center plate or front plate or back plate that's not visible to eyes?
2) shall i switch to OEM seals to try out ?
3) they found a weak spot on the back plate, but it's not causing any leak, but the wall is thinning. can i weld them to fill it up?

the wall thinning picture is as below

 

When you lose a coolant seal you wont necessarily get water in the combustion chamber. What you get is exhaust gasses passing the seal and going into the cooling system. This pressurizes the cooling system as you experienced and forces coolant into the overflow. Likely your overflow is overflowing and dumping coolant, that is why you need to keep adding water.

 

Another possibility is something is wrong with the coolant overflow system, either the line going to the overflow tank was blocked/capped off or the radiator cap was VERY stuck closed. This would also pressurize the hell out of the cooling system.

That iron MAYBE could be fixed, but I wouldn't trust it. Good used irons aren't that expensive, I'd replace it.

I've heard many good things about Pineapple Racing's coolant seals - I'd either go with theirs or OEM.

Dale

Dale

 

how yeah... i also found out that my rotor housing has a medium sized dent on close to the Water jacket sealing point...

can i just seal that dent with epoxy or any sort of chemical ? or i just get a used housing ?

 

can i use the tig weld to cover the dent/hole ?
or strictly no welding should be done on the rotor housing ?

 

That dip looks like its right in the path of the seal, where on the housing is it, as in what portion of the housing?

I would weld it up, if the rest of the housing looked good, and if its actually on top of the seal. I have done things like this successfully in the past. really you could use devcon or JB weld, but tig welding is better. Afterwards you would need to make the welded portion perfectly flat.

 

How often did you change your coolant? My dad's motor had some of the same issues (pitting on the rotor housing in the same area, failure of the thin wall on the iron) and it was caused by his (ridiculously negligent) lack of maintenance.

 

Ha, my answer for anything coolant related that causes extreme pressure: try changing the thermostat. It's a $10 part that takes about 10 minutes to swap out. To think, I spent hundreds of dollars on parts I didn't need, when it was just a bad thermostat...

 

Have you guys had success welding housings?

My experience is that welding anything distorts it.

Dave

 

my front iron failed in the same spot due to corrosion. Wasn't my fault as I got the car with 90k plus on it! Its really too thin there though. just get a new used iron.

t

 

I agree, I would either replace it or use jb weld before I would weld on it

 

agree

 

tig welding that tiny dip on the rotor housing wouldn't be a problem, welding does warp things but this isn't a piece of sheet metal, its a considerable mass of aluminum.

 

the thermostat opens perfectly when taken out to test on hot water....
even my mechanic took out the thermostat, basically not running any thermostat... the coolant pressure still goes up sky high....

the biggest question will be if i able to tig weld the particular spot.. and making it perfectly FLAT without grinding the other surfaces that doesn't need to be fixed..........

btw, what is a JB WELD ? does it work on aluminums ?

 

seems like JB weld got higher chance to make a FLAT surface than TIG welding that i need to grind.. chances of grinding more than i need is high as well....

hunting for JB weld in my country now...

as for how often i change my coolant, earlier my housing was damaged at teh same location but this one was from a front clip. it had already corrosion on it but it wasn't serious... i only had my coolant in the engine for 1 year... the corrosion only increased around les than 5% from the day i put my engine back.

so, green stuff ethelyn glycol is a go for Mazda OEM seals right ? how about red toyota coolant with water wetter ?
some day it'll kill the seals, some say it will prevent corossion on the housings.

 

Where are you in Malaysia, I was there for 2 weeks in December and didn't see a single Rx7?

 

i'm in Kuala Lumpur. i found JB weld. and other brand that does the similiar thingy.

i bought one Araldite, rapid steel. same epoxy steel raisin.. gonna seal the hole on my rotor housing. hopefully it doesn't shrink. and i'm gonna replace the center steel plate to another used one.

and i'm gonna use Mazda OEM seals. hopefully it solves my problem...

oh yeah regarding RX7 in malaysia.... nowadays it's extremely rare... driving around a month you hardly see one or 2 on the road... people here either crashed it or sold to East malaysia or they keep their car at home not running it waiting it to rust and engine to blow.

on my database, i have only 20 over to 30 combined FC and FD owners only...

 

Use green coolant, I'd stay away from the red/orange/purple stuff.

 

+1 If you have excess pressure, a blockage like this is THE cause.

Dave

 

the overflow tank was bubbling after the engine heated up more than 90 degrees celcius.. less likely cause by blockage.

engine was torn apart, didn't see any sign of blockages.