luism786

My 93 FD has an overheating problemthat I cant figure out. The car strts and runs erfectly fine and starts warming up normally until it gets to about 70C (from the power Fc commander) then it drops about 8-10 degrees and after this it starts to rise again until overheat. Sometimes there is a diference from what the gauge is reading vs what the commander is reading. after i turn off the car the coolant is low, so i fill up the coolant again and try it later and it does the exact same thing. This is a rebuilt engine, new thermostat and the water pump was reused but its less than a year old. The overflow bottle is not getting used, I thought it could be a leak in the hose for tht or the bottle itself but i put another hose routed to a coolant bottle and it didnt do anything either. I have aluminum AST and also replaced the cap on it. Im running out of ideas.
Some details about the car:
Freshly rebuilt engine with street port, Koyo aluminun radiator (Nflo less than a year old), single turbo without coolant (all turbo coolant liness capped), aluminum ast, All lines were replaced or capped (the ones not needed), tried bleeding the system several times. Not sure what to do next.
This is all that I can think of right now. Any help is appreciated, I havent had the chance to drive it since the rebuild!!! Also Im in England in an area with very little support for RX7 so please bear with me as Ive had to learn a lot on how to deal with this car by myself. Thnks to anybody that helps

diabolical1

iTrader: (3)

are you getting any smoke/steam out the exhaust?

luism786

No. This is pretty much what caused the engine to fail originally iin the first place, although at the time I thought it was just a coolant seal issue but there was an underlying cause and after the engine rebuild (which in fact had a bad coolant seal) the car is still overheating. But there is no smoke other than the smoke from the premix.

Sgtblue

iTrader: (16)

If you're confident that the system is full, the next step is to pressure test the system. Here in the States most of the chain parts stores will lend (with a deposit) a pressure tester. It's bascially a pump that attaches to the filler neck with a guage. Pump it up to ~ 15 to 18 psi and wait a few hours to see if it holds. If it doesn't, you have a leak somewhere. That's letting air into the system that may be responsible for your symtoms. A bad hose, bad hose connection, bad cap(s)...or possibly a failed or pinched coolant seal.

Who did the rebuild? Is it practical to take it back and have them address it?

luism786

I did the rebuild myself since the area has no rotary mechanics. Sadly this isnt the good old states where we can get stuff loaned from autozone but Imight be able to borrow the tool from the base. However the system seems to be holding pressure because i went to open it yesterday and it still had some pressure left in it. I will reply with the results when I can get the tool.

diabolical1

iTrader: (3)

perhaps housing warpage from the pre-build overheating?

Sgtblue

iTrader: (16)

That's strange then. When the coolant heats up from the running engine, it expands and goes into the overflow tank. When you turn the engine off, the coolant begins to cool and contract. That creates a natural vacuum which draws the coolant back out of the overflow. So once the system is completely cooled to ambient it shouldn't be holding pressure. In a sealed full system, it actually should be holding a little vacuum.

luism786

Both housings are new and the center plate is different (used but in good condition). Im about to bypass the heater core to see if that's the problem, I've read some poeple having very small leaks from it and that causing some weird stuff. Sadly all the places ive been to to ask for the pressurizing tool don't want to lend it or rent it out; they want the car there. Right now I consider the car undrivable because if the engine is still good it definitely won't be if i drive it for 20 minutes to get it to a shop that has a pressurizing tool but still no knowledge about rotary engines.

Question: Where does the temp gauge get its signal from? Because the gauge and the ECU read different temperatures at times. I'm guessing the ECU gets it from the sensor close to the water pump and the gauge from the one on the rear plate but im not sure. Correct me if I'm wrong.

Sgtblue

iTrader: (16)

You're correct if your asking about the stock gauge. That completely worthless non-linear stock gauge has a sensor in the rear iron, under the oil filter pedestal. The ECU will take it's readings from a sensor on the back of the waterpump housing.

I keep forgetting about this thread, but it might help you figure out the cooling system and how it works on the FD. You may have already seen it...but figured I'd mention it anyway..... https://www.rx7club.com/3rd-generati...thread-571088/

Sgtblue

iTrader: (16)

^Pressure test the system.
---> https://www.rx7club.com/new-member-r...being-1014483/

RotaryEvolution

iTrader: (30)

ok people, read the responses.

PRESSURE TEST THE SYSTEM!

misterstyx69

iTrader: (142)

OK People..Thread Cleaned up.
To those posting Info.Thanks you very much.It is appreciated.
BUT,If you have NO info then Do Not post.
The last guy here went BYE-BYE for trying to sell engines,disrespecting Members,thread crapping and not READING any rules of Posting.

ChiGod666: IF you have a problem then Create your OWN Thread.
That goes for you too Deuces..Sorry man..Be respectful.
No Butting in Line.You just got Caught by the Bouncer.
This means NO Thread Crapping People.
Do not Try to Take over someone else's thread with YOUR problem.They took the time to construct a Thread pertaining to THEIR problem.
You can do the same.That's how it Works here.
It's a TECH section,you get to post your Problem,BUT you do have the authority to create one for other members.

Any more Useless Crap in this thread I start a Clean up.Trust me,I can make the problem disappear.

STYX (MOD)

luism786

Sorry for the late response but work has had me swamped and I haven't been able to work on the car. I bypassed the heater core and it started leaking from the plastic connection that goes to the block from the core, I don't know if this is the original leak or I just broke it when I was removing the hose from it. Its pretty hard to see and I don't know how to take this plastic fitting off. Anybody know how?

Sgtblue

iTrader: (16)

Black/brownish fitting on the block below the oil filter pedestal? IMO use a pair of channel locks and twist the damn thing off. The double worm gear clamp the new hose back on. That fitting is a pita and tends to break one with age....as you now know.

luism786

Do I just kind of unscrew it or just twist it to break it off? I'm assuming its attached to a metal pipe or something of the sort. I dont want to break anything else in there.

Sgtblue

iTrader: (16)

^Sorry for the poor grammar in my previous post...on the damn cell phone w/o glasses.
Anyhoo....I removed mine but it was when the engine was out. IIRC there are some indents to push and it will slip off....it sort of reminded me of my air hose quick-connects. I also recall that metal nipple being pretty robust and the plastic connector being brittle. If you can't get it off with the indents, maybe carefully crushing it and taking it off in bits will also work.
Wasn't able to find pictures to help, but found several other threads suggesting to leave it off and just double clamp. That's what I did about 6 yrs ago and no issues since.
https://www.rx7club.com/3rd-generati...ook-up-308110/
https://www.rx7club.com/3rd-generati...apped-1011603/
https://www.rx7club.com/3rd-generati...estion-403850/

luism786

Finally was able to bypass the core, everything was going normal but after a few minutes it overheated again. I just ordered a pressure test tool and a bleeding funnel since no one around here will rent it. I can't wait to be back in the states where I wouldn't have this issue. Anyway it should take about a week for that to get here and Ill post the results of that when I can get it done.

luism786

Pressure tested the system. Went up to 17 psi and the needle didn't move. Found a couple of very minor leaks and fixed them on the spot. Filled it back up with coolant and attached the bleeding funnel full of coolant. It still does the same thing . Im waiting for it to cool down again and i'm going to flip it around because there is a very slight incline in my garage. hopefully that gets whatever air is in the system out of it. I definitely have run out of ideas after this.

samjaza78

Does it do this while driving, or just sitting at idle? How well is your fan working? Did you replace the radiator cap?

luism786

The radiator cap is fairly new and I tested it today and it's working fine. Right now I haven't taken it for a drive because it heats up too quick for it to be safe. Today I hooked up a bleeding funnel to and after a couple of times of turning it on and off and squeezing the hoses it gave some good signs but it's still behaving erratically. I let it cool down and I'm about to go back to try it again. Hopefully it's just air trapped in the system.

impactwrench

I have installed new thermostats before that turned out to be bad.

dvaz

Try a different thermostat one that has a lower temp rating maybe that helps