I have a lot of parts like Koyo radiator, FC thermoswitch, aluminium ast etc. sitting in my garage waiting to be installed but I was holding off to do everything together but looks like the problems couldn't wait.

The other day add coolant light came on for the second time in a year. First one was caused by reservoir filler neck/hose being loose (fixed with a tighter hose and some clamps). This time however after I added water I noticed during cold start there is water sound coming from behind the dashboard area like someone left the tap on. There was always slight water sound coming from behind passanger side dashboard area but went away as the car warmed up, this time however it is louder and much longer.

I found this thread about the problem:
https://www.rx7club.com/showthread.p...ound+dashboard

But:
no visible water leaks from any of the hoses,
no sweet smell coming from the exhaust,
performed bubble/champaigne test, result no bubbles,
fans come on,
temp gauge is normal,
slight water leak from the radiator filler cap when the car is driven for long,
today when I drove the car it leaked some water from the reservoir but that may be because I overfilled it,
the radiator filler neck has some white gasket/filter/block off kind of stuff (pic below), I don't know if the car comes like that or if it is made by the previous owner

Any ideas what may be causing the problem or what I should check next?

 

Never heard of this...

 

The previous owner had many "genius" solutions to the problems he faced I am not sure if this is one of them; a white plate/filter as seen in the pic

 

Is your heater on at cold start? That sound coming from fluid movement at your heater core?

 

Heater off.

 

Try bypassing your heater core?

 

Just to understand, what will that do, is it for the water sound or loosing coolant?

 

rules out the heater core for both sound and losing coolant. Heater core was just a shot...most likely there is a leak somewhere that you just haven't found yet...puzzling situation...hard to diagnose.

 

it would only take about 5-10 minutes to run the bypass. Quick easy check before you really start into it.

 

use a cooling system pressure tester.

 

I am just hoping the problem is not coolant seal related.

 

Tomorrow I'll try to bypass the heater core. While at it should I remove the white plate (in the pic I posted) under the radiator filler neck?

 

what the hell is that for? Is it a block off plate or just a filter? hard to tell in the pic

 

part filter part block-off i tried pouring water in there and it almost sits there moves down at very slow rate. But whatever it is, if it's not oem, I'll remove it.

 

I know the sound your talking about. I've been getting it as well towards the end of last summer when theres air bubbles in the coolant. Saw I had a sweat on the lower rad hose so i'll be changing that this weekend before I take the car out hoping that was the issue but I'm not sure.

Keep us posted if you find anything.

 

I did not get a chance to do further tests and troubleshooting yet. If work allows me to, I will do it this week or early next week. However I went for a drive so the battery stays alive and noticed that the water sound coming from behind the passenger dashboard area is now constant. It's like someone left the tap running. I think if I can find the reason for that, I will find the reason for coolant loss

 

Parked the car for few weeks, came back today, started the car, add coolant warning light came on before I started driving. Added water (less than half a litre) then I noticed some water on the floor under the exhaust. No sweet smell though.... Coolant seal???

My car always smoked at start-up (whiteish/blueish and lingers around) and I always thought it was due to damaged 2nd turbo cause when I park for a long time (when the car is cold) it drips oil from that area but I didn't care, as I have a single turbo on the way.

But now water near the exhaust pipe makes me think it's the coolant seal I will let the car sit for a day or two and then start it and check. Maybe I should let the car sit longer I am not sure.

At this stage, I'm just hoping it's not something that requires an engine rebuild Any ideas about the approximate cost if I was to rebuild it myself vs. buying another engine from one of the rotary shops?

 

My car made this 'rushing water sound' near the glovebox when there were air pockets in the system. This could be caused by a recent coolant flush... if so you might want to try bleeding the air from the system, and be sure to top off the coolant every time the car runs for the next few days/weeks.


In my case, the air pockets were caused by a coolant seal problem. The car began showing symptoms after boosting hard when the engine was still cold (~75k miles?). I drove the car pretty hard in hot weather for a couple years before that, so the boosting on a cold engine may just be a coincidence. The coolant at the filler neck was always a bit low. Some days it was not low at all, other days it required over 0.5L to bring the level up to normal. If the engine ran for a long enough time, it would eventually push water (and steam) out into the overflow tank. This would cause the low coolant buzzer to alarm and the coolant temp to get hot. If the engine was started cold and then immediately shut off (less than 30 seconds of running the engine), then remove the coolant filler cap, you could hear a 'psssh' sound from excess pressure/combustion gases in the system. With a healthy engine, coolant pressure should not increase until the engine begins to warm up after running for a minute or two.

At first, the engine would run for over an hour before starting to overheat. I kept driving it (sometimes gently, other time less gently) to see how long it would last... I got at least another 3000 miles of use, it wasn't enjoyable having a car that was not performing 100%. Eventually this time got shorter, until the low coolant alarm was turning on in less than 15 minutes and it was impractical to drive the car at all.

 

Thanks Scotty, I am letting the car sit for few days to replicate what happened last time. I'll start it up in a day or two, and check if water is coming out of the exhaust. I guess that'll confirm water seal damage.