Hey everyone,

I finally got my car running tonight after almost a year. I have replaced my AST with a Bypass kit that I bought from Mazda, it is for the radiator on the FC models. Same as M2's kit. My question is this....the kit I got from Mazda came with a pressureized cap, and our cars use a regular cap. I was using the pressurized cap since it came with the kit, but my car keeps overheating, so I have to pop the cap, get some fresh water in the neck and let it cool down, I put the cap back on and it starts to overheat again....could the cap be my problem, or is there something else going wrong?

Does anyone have the M2 AST Bypass kit and know what their cap looks like that came with it?

I am having some other problems as well with all the changes my car overtook.

My coolant light comes on and beeps, could be that cap as well though.

My oil light comes on, but the oil is full, the pressure gauge reads fine, I am assuming it may be my oil sensor in the pan. I am going to check it out as well.

My Overheat Exhaust System light stays on.....don't know why? What causes it to go off? The O2 sensor? I have an exhaust leak in my DP where I used to have an EGT gauge mounted, but now I just have a bolt in it and it is leaking around it. That will be fixed, but the overheat light going off is my question.

The car seemed to idle ok, outside of the searching for a new idle, but it ran fine, then it started to overheat.....I am hoping it was that cap.

Oh....one more thing. My fans are not coming on with the car running....but once I shut the car off, they come on and work fine. They are setup to come on at 83'C via the PFC. They don't....but they do stay running until it drops back down to 82'C then they shut off....so they work right when the car is off, but when it is running, they don't come on at all. Why might that be?

For the record my car has recieved a new BNR ported motor, new T78 turbo kit, huge fuel system, HKS Twin Power, Greddy 3 row FMIC, AST Bypass kit, Hyperground ground straps, removed ABS, PS, and AC.

I have a loose ground on the started side of the wiring harness....it is a thick 2-4 gauge Black wire w/ a yellow stripe. I think it used to ground my PS, but now it is not grounded.....did it ground more than just the PS? I tried to find a place to ground it, but I couldn't. Does it do anything?

Sorry for the long post.

Thanks,
Scott

 

You definitely need a pressure cap with the AST bypass. There has to be a pressure release somewhere in the system. In stock form, it is in the AST cap, but if you get rid of that, you need one on the filler neck. A faulty cap would not cause your car to overheat. I think you should investigate your fans a little further. If they don't come on, then you will overheat, and if you do this too often or severely... it's time for a new motor.

 

The malfunctioning fans are your biggest worry right now. Do you have a way to monitor coolant temps? Be careful not to warp those rotor housings.

One thing you can try--remove your a/c relay and turn the a/c on with the cabin fan setting on 4. This should trigger your underhood fans......

 

I am going to start messing around with it some more today. My question about the cap is that the AST Bypass I installed does not have a cap like the stock one on the water filler neck. It has a pressure block that covers up the overflow hose until it reaches a certain pressure than the cap gets compressed and coolant is aloud to flow between the overflow and the cap nipple. I am wondering if I should be using that cap or the stock cap that goes on the waterneck.

What could cause the fans to not work when the car is running, but to come on when I shut the car off? Is there a plug or something that could be broken? I will try that AC trick....I don't have AC anymore anyways, so it won't hurt to have it on all the time if it will keep my fans running. I have been trying to burp the system over and over to make sure I don't have any air bubbles. I may just be low on coolant....or have air pockets in there. I have the AWS blocked off as well as the TB Coolany bypass so no coolant flows near my TB anymore.

Any more info on this would help a ton.

Thanks,
Scott

 

You NEED to use the pressure cap Mazda supplied with the neck! Basically that neck acts as a mini AST now, & the system needs to vent off pressure or you'll blow hoses & gaskets (even coolant O-rings!).

Since the AST is gone there are more places for air to hide in the system. Just keep cranking it & letting it get up to about 88°C then shut it down & let it cool, then fill it again. This takes a lot longer with the AST removed. Just keep trying!

There is a temp sensor over the stock main cat. If you've got an open port spewing exhaust directly onto that sensor it's going to be your cause for the Exhaust temp lamp.

Good luck with the fans. Stuff like that just needs troubleshooting...

 

Cool, so use the pressurized cap. Everyone so far has said that from here, other forums, and friends over the phone.

The fans is throwing everyone for a loop though....noone can understand that deal....neither can I.

Under the passenger seat under the carpet is a sensor that probably isn't plugged in which grounds my Overheat Exhaust Light, so I am going to check that and make sure it is grounded properly. We'll see, I am not too worried about that right now....I am more worried about the fans.

I tried to work on it some today, but the ****** wouldn't start. My battery is toast, I went to get it recharged and tehy said it was bad. It is only 6 months old and never used, so I am going to return it to Interstate for a new one.

Hopefully everything will be worked out tonight. Just got to keep burping the system and get all that air out of there.....a new motor has all sorts of air in the coolant passages, so we'll see.

If anyone has any ideas on those fans, please chime in. Thanks to everyone else so far. Wish me luck.

Scott

 

You need to connect that ground wire that was on the P/S pump. That could be part of your fan problem

 

Really? Damn, I will have to try that. I just could not find a place anywhere near by to ground it. I will make my own ground if I have to. Someone told me to ground it to the middle plate between the rotor housings, they said it went there and not to my PS. Who knows? I will go ground it and let you know though.

Thanks,
Scott

 

Well, now that I read over your situation I'm not too sure about the overheat lamp. The Power FC uses that as a check engine lamp. It supposedly lights when your injector duty goes to high, or your boost goes too high. I've never actually seen it on though.

 

Well my injector duty is down at like 8-9% and there is no boost.....just vacumn. I think the highest my injector duty hit was like 10.3% when the car was searching for an idle and it kept surging up and down.