magnumP5's RX-7 Build Thread
- Thread starter magnumP5
- Start date
Glad you made it home, buddy. Even if something is a little wonky with the old girl, I'm sure you'll take care of it and fix it up the right way. Still, you gotta love that older car still kicking ass out there on the track!
Well I'm 90% certain the engine needs a rebuild. After driving more recklessly than I'd like on the street and then revving the engine in the driveway I finally got the low coolant buzzer to go off again. I also figured out that what I thought was coolant boiling was actually air (or gas) escaping the overflow tube into the overflow bottle. A few times a considerable amount of coolant also shot out. From what I read this is very likely a cause of a failed water seal so combustion gases are partially pressurizing the cooling system. If there is a failure it has to be small because before I did all that previous stuff I pulled the EGI fuse, cranked the engine a few times and inspected the spark plugs. There was no evidence of coolant on the spark plugs but they don't look so great. See pictures below (rotor 1 is first, then rotor 2, leading is on left and trailing is on the right)
PrinceValorum
Member
- :
- 95 626 FS, 89 Toyota Derux 4x4
That sucks, man. I hope you find it in yourself to stay true to the rotary's and don't go with something with 8 cylinders...
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No intent on going with pistons - too many moving parts. I am at a bit of an impasse though. On one hand now that the engine needs rebuilding I'm tempted to start enacting my long-term engine plans (4-port N/A with ITB's, standalone, etc.), but on the other hand I want a running car this season. It's too bad both options require different engine blocks...
Wasn't good that it overheated, but I'd pressure test the cooling system first before you do anything. Those plugs don't look that bad to me but put in a new set and see how it starts. Any initial stumbling on cold start-up? Steam or faintly sweet smell? Does it continue to overheat?
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I've been neglecting this thread a little - I pressure tested both the radiator cap and cooling system last night. There is a small tear in the cap - small enough that I didn't think it was an issue, but apparently the cap can't hold more than ~9 psi and even then it was still dropping. It still releases pressure at 0.9 bar (13 psi) but it will not hold at 12, 11, 10, etc. psi. I brought the pressure in the system up to 15 psi and let it sit there. It slowly dropped from 15 psi to 14 psi in about 20 minutes. That's not perfect but this should indicate there isn't a massive water jacket o-ring failure. No smoke or sweet smell at start up. Plan is to replace the radiator cap and go from there. Here's to hoping it isn't as bad as I thought!
You're telling me. I posted a picture of it on another forum and the immediate response was "the cap is crap, replace it". Needless to say an order for a new radiator and thermostat was placed with OnlineMazdaParts. Once those come in I'll install them and drain/flush/fill the system with distilled water and a little Water Wetter. If the problems go away I'll probably splurge on an aftermarket radiator (Koyo N-Flo) and all new lines and hoses and do the proper distilled water/anti-freeze/Water Wetter mixture. Hell, even if it doesn't fix the issue I may buy all that anyway as the source of the problem could lie with any one of those components. Here's to hoping my season isn't over after all (God I'm such a pessimist)!
I'll still be attending the Mitty regardless. It's demonstrated it can drive 2.5 hours with no issues and I can always bring water just in case. If it absolutely doesn't agree with me I can always just take the truck. It's no fun but I already volunteered to help (and paid for my hotel) and I'd hate to back out.
PrinceValorum
Member
- :
- 95 626 FS, 89 Toyota Derux 4x4
Wow, I can't even imagine how much of a relief that must feel like. I didn't really want to say something stupid at the track, but one time I bought a car and it had rice and spaghetti noodles in the coolant system, not even kidding. Sometimes you just don't even know what could be plugging things up, lol. Hopefully yours is nice and clean since you said you already flushed it before.
Haha, I remember reading about that. Anyhow, I'm not getting too optimistic just yet. Sure, I now know the radiator cap wasn't holding the pressure it should, but the cooling system was depressurizing slightly, SOMEWHERE. Unfortunately there are a lot of possible explanations ranging from a very small failure of a rotor housing (worst) to the pressure tester not forming a perfect seal (best). When I start the car after I've received the new radiator cap I'll be sure to watch for any white smoke in the exhaust. This will indicate if any water was pushed in during my pressure test.
I figured I could always ask but I didn't want to inconvenience anyone. If I do take the truck down I'll probably catch a ride with someone to the track (in a Mazda) though.
Radiator cap and thermostat should be shipped today. Here's to still hoping those will correct the issue!
I also went ahead and purchases a new Koyo N-Flo aluminum radiator. Even if the stock one is fine the cooling system hasn't proven it isn't up to the task of track duty. Even though I got it for a good price it doesn't look like it'll ship until the 27th >.< I'm also looking into underdrive main and alternator pullies to help combat water pump cavitation. Maybe a underive water pump as well. The difficulty is finding a combination that does not underdrive the already nearly inadequate stock charging system. I may pull the trigger on a complete new set of radiator and heater hoses and a new water pump as well. Might as well update the entire system while I'm at it, right?
I also went ahead and purchases a new Koyo N-Flo aluminum radiator. Even if the stock one is fine the cooling system hasn't proven it isn't up to the task of track duty. Even though I got it for a good price it doesn't look like it'll ship until the 27th >.< I'm also looking into underdrive main and alternator pullies to help combat water pump cavitation. Maybe a underive water pump as well. The difficulty is finding a combination that does not underdrive the already nearly inadequate stock charging system. I may pull the trigger on a complete new set of radiator and heater hoses and a new water pump as well. Might as well update the entire system while I'm at it, right?
For a car that's going to see track duty, absolutely. Personally I would focus most on the cooling....I think hoses are a no brainer. The track will find any weak spot and puking coolant all over the track can mess up the day for you and others too.
It's a long thread and I can't remember if you've mentioned something about it already, but don't forget oil cooling.
There really aren't too many options for oil cooling outside of verifying the stock unit isn't leaking and upgrading the lines with braided steel ones. The only stock replacement I've seen advertised is a PWR unit, which costs upwards of $500!
Apparently my Koyo radiator is ready to ship! That's a lot faster than April 27, which is what the order confirmation email said. I guess I should go ahead and buy all the hoses now!
Sorry, after checking it looks like the FC oil cooler is already a pretty good unit. Apparently MAZDA COMP used to offer an upgrade, but I didn't check to see if it's still available. I doubt it. So maybe just a new set of OEM lines if they're showing their age and your golden.
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I haven't seen a parts catalog from them newer than 1997, but the one I've seen has the Mazda Comp. oil coolers crossed out so I assume they're no longer available. I am looking into the underdrive water pump pulley but I'm trying to determine if it's single or double "sheaved". I need a double sheaved pulley because I still have the airpump installed and need a provision on the water pump pulley for its belt. Also, for some reason Mazda Comp. says the underdrive water pulley MUST be used with an underdrive main pulley although I can't see why. I'm hesitant to underdrive the main pulley, and therefore the alternator because the car still does see some street use and I do still drive it to and from the track. The alternator output is weak enough as it is...
Well, the new radiator cap didn't seem to do anything. Somehow there is still a constant stream of air/gas going into the overflow bottle. Every now and then some water comes with it so pressure is being built up somewhere. Additionally, when I remove the radiator cap with the car running and warmed up it just keeps bubbling like the system never seems to be fully bled. If I add more water while it's running it seems to just want to push that and more out.
Time to start pulling things apart now?
Time to start pulling things apart now?
