Hey guys my fd runs really well on highways (tested up to180km/hr) but at low speeds (the slower the worst) the car will overheat rather quickly. Doesn't blow white smoke and bubbles don't come out of overflow tank on start up.
Coolant buzzer is on at low speeds not at high speeds
Previous owner used tap water for coolant
Coolant overflow tank is cracked and can only hold about 1L before it leaks
Pretty sure I have some Japanese electric fan system and it has an electric fan controller that I don't know how to use properly
1.) water pump needs to be replaced (would I just have to replace the water pump $120 or the big thing attached to it $360?)
2.) replace coolant overflow tank (duh)
Any other ideas as to what it could be?

 

Replace the overflow tank first so the system can build pressure. Then see how it goes.

 

Read your own post. You have a sketchy fan set-up, the system maybe less than clean due to mineral deposits from tap water, you have a cracked overflow tank and a bad waterpump. And since the low coolant level alarm is going off, your system isn't even full.
Because of the PO's neglect and ill-advised modifications, I might look to make sure you have a belly-pan on the car. BTW, do NOT rely on the stock temperature gauge. If it moves higher from just short of 9:00 o'clock, you've overheated.

And no, you don't have to replace the waterpump housing. Just the water-pump with a new gasket.

 

The overflow tank isn't part of the pressurized system. You could leave the hose going to it disconnected to atmosphere and the system should still build pressure.
Although this made me think the OP could also check/replace the filler/AST caps in case they aren't sealing and letting air in the system.

 

Thank you very much guys ill look into all of that and order the parts today. It has aftermarket ast cap. Sadly I also found out that I have a boost issue as well. It's off and on but sometimes when I'm driving the car the boost gauge will reach .05 before bogging out and back firing. So it has fo be something in the stock twin turbo system and I'm considering waiting until I can go single turbo because this system is really confusing to me.

 

A stuck thermostat can prevent coolant flow to the rad. You might check/replace that as well.

 

Some cars they are. I don't know the FD very well, but thanks for the info.

 

Ill replace the thermostat too thank forgot about that. On a side note does anyone know where I can get a check single turbo kit? Like a used one or something, google isn't helping much.

 

That is what I was thinking also, as its easy to get to and much cheaper than a water pump. I saying that the impellers on the water pump could be worn. But with regards to the thermostat it could be getting stuck. If your car has a power FC it will show you temps its getting too. This is also a good tool in order to check to see what temperatures your fans are coming on at.

Process of elimination is key I suppose when diagnosing issues and its always good to start with the easiest most logical.

If your coolant buzzer is sounding it means your coolant is being pushed out somewhere, having a expansion tank that is cracked probably isn't ideal as it might not be able to suck enough water back into the system when cooling down. This in tern will cause over heating issues as your cooling system will no longer be bled correctly as now your cooling system will be cavitating air. Pretty important the coolant system working well in all FD's

 

Thanks guys ordered the parts, now to deal with the turbo issue :/.

 

The water pump impeller almost never gives a problem . I don't ever remember seeing one worn out from the coolant action but anything is possible ..

Sgt. blue gave you a very good suggestion . I'm betting your fan system isn't working proper or not at all . The reason your temp stays down on the road is all the air being forced through the cooling system from the car speed,, as soon as you slow down less air flow and hot engine . Hook that fan up direct to power so it runs all the time and try it , If the cooling system is worth having it should run at a reasonable temp with the fan running constant putting on the street or on the highway .

 

Thanks that's a good suggestion but I'm not too sure how to do that because it has this aftermarket electric fan system.

 

yea well I'm not much on wire colors and such . There are no doubt lots of guys that can help you here but you must know someone that can monkey wire the fan to try it. Have you ever seen it run ? Does it have a on = off switch somewhere maybe on or under dash that is not being used proper ? put up some pictures of the cooling system so people can see what you have and I'm sure someone can help .

 

Thankfully all of the fan relays appear to be present in that picture. With any luck, the previous owner just hard-wired the aftermarket fan and the plug/connector for the stock fans is hanging down there somewhere.... ready to be plugged in to the stock fan assembly. And those come up for sale in the 3rd Gen. Parts for Sale section.
The question is, what radiator is there underneath all that. Hopefully it's an FD specific radiator with the mounting points for the fan assembly.

 

Car was driven down back road before picture ignore the dirt cleaned it off already lol

 

Hard to tell for sure but looks like OEM radiator and maybe the fan assembly connector hanging down in the second pic. The first pic suggests a leaking cap and the need for a coolant flush.....soon if you don't part it out.

 

Thank you for all you're help, it's greatly appreciated! Which cap would I need to replace?

 

All that rusty-colored stain below the filler cap is the clue. But I'd replace both caps if you still have the AST. They don't cost alot, but IMO stay with .9 bar (13 ps?) pressure cap.
Download a copy of the Factory Service Manual from the 3rd Gen. Section FAQ stickys and search that section for threads about changing coolant and burping the system.

 

Hopefully you don't have a 2525 painted on your roof. If you get a call from Denis Hopper, don't answer it.

 

Thanks man!

 

What do you mean?

 

Its a reference to the movie Speed. Its an oldie but a goodie.