Subaru Forester Owners Forum banner

1 - 9 of 9 Posts

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #1
Now that the temperatures are plummeting, AOS w/o coolant heating that I installed at summer is really bothering me. In other words I’m afraid that it will freeze and lead to catastrophe. Before when I had Saab 9-5 which was notorious for clogging oil sump strainer I made a display for oil pressure from VDO oil pressure sender, pic microcontroller and display for readout. I was thinking the similar solution here. Instead just using buzzer and hiding these behind the dash. Program it so that at low pressure it would beep slowly and higher the pressure, higher the beeping interval. So that it would be completely hidden until there is a danger. When it would beep, you just pull over and let the engine radiant heat melt the AOS and hoses.

Where would the pressure sender be located? If there were any unused plugs on top of engine, that would be perfect. Anyone knows is there? Other possibility is the front breather located under the alternator, install T-fitting to the hose as close to the engine as possible. Back breather under the intercooler won’t work as there is pressure when in boost.

I measured the needed force for dipstick to lift off and calculated equivalent pressure to be ~2.7bar / 38psi. Which is quite high. I wonder would some of the rubber seals if any pop off before that. Due to not knowing is there some other place giving up earlier I was wondering to set the alarm starting from 0.2bar to 1bar (3psi-14.5psi). Basically my understanding is that in any case there should be no pressure at all in the engine when everything is ok.

What are your thoughts? Am I being paranoid, or does this make sense? Of course maybe easiest would be just slit the hose longitudinally inch or so and it would release the pressure if necessary..
 

·
Registered
2017 Forester XT Touring
Joined
·
285 Posts
Was it the AOS lines or the AOS itself that froze? If it was the AOS itself, plenty of new ones out there with coolant lines to keep them hot. I have the Crawford AOS and despite cold weather and frequent short trips, no issues.

Sent from my Pixel 3 XL using Tapatalk
 

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #3
It hasn't frozen yet.. I'm just wondering should I be prepared of it.

Any case, decided to give it a try as there is no harm and it will give me peace of mind. First part manufactured. That's the sender unit adapter made from POM for better insulating properties...
 

Attachments

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #4
Took almost two months to get all the necessary things to have this finished. Now it's ready and waiting for the weekend for installation. Pressure sender in the picture goes to that black adapter. That assembly goes below A/C compressor breather hose. PCB behind the dashboard and led to some of the unused switch dummy cover. It is programmed so that 0.1 bar it starts blinking with 1 hZ frequency and every 0.1 bar frequency is +1. In the event of pressure, every ten seconds it will tell by one second on blinks what is the pressure eg. ten blinks is 1 bar. If signal wires are shorted light will be continuously on to indicate error. Hope it will never blink..
 

Attachments

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #6
@MNTNDRMNGFXT Thanks for liking.

Now it's installed. Was bit tight for the sender as it is relatively big. There is like 10 cm / 4 inches hose from the connector until the sender unit, but was not able to make it any closer. However that first part of hose is so close to the engine block that most likely it's the last part to freeze. Also some padding between the sender unit and AC compressor. (first pic)

PCB fitted to the fuse holder. There were unused fuses so I used the #23 for supplying the pcb and added pin for the corresponding connector. Fortunately it was behind ignition accessory so no permanent power there. (second pic)

Led I installed to visible position on unused button cover. (third pic)

Not everything went so smooth. Even though I had built in low pass filter in the PCB it was getting erratic led blinking. I had in the first place grounded the sender unit to the engine. So grounding the sender to the PCB negative pin solved the issue.
 

Attachments

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #7
Have had this now for bit over two months. Haven't had too cold weather but I've noticed some pressures in the system. And no I don't think it is due to freezing. I have noticed odd slight pressures in low boost situations. In some occasions when boost less than 0.6bar / 8.7psi I’ve noticed minimum registered pressures in the system, which is 0.1bar / 1.5 psi. When I hit the gas pedal for higher boosts, pressure is gone in the system. So I interpret it that on low boost it leaks pressure to the engine somehow… I took the PCV valve under the IC and cleaned it in ultrasonic cleaner to rule out any jamming of it. Still I notice some pressure build up.

I’d see that if it were combustion gasses through rings why it goes away in higher boosts? Or maybe the PCV valve is worn and won’t hold pressure in mild boosts. Boost pressure leaks to engine and is extracted to the front breather under the AC compressor and due to restrictions in AOS can be seen as slight overpressure inside the hose. Or so much blow-by gasses past rings that the pressure goes from front breather and due to restrictions in AOS can be seen as a small pressure in the hose. Front breather valve is closed due to higher pressure in intake manifold. Ouch, wouldn’t want this to be the case. Please help me to diagnose what could cause this?

I assume it leaks boost as since I got this car it has had mixed personality. Eg. sometimes it pulls like mad and sometimes (quite often actually) feels like it is lacking plenty of horses. Haven’t driven other XT’s whether it is feature or an issue.. I’ve done the Danoz fix for clamps though.

Thanks
 

·
Registered
2017 Forester XT
Joined
·
185 Posts
Have had this now for bit over two months. Haven't had too cold weather but I've noticed some pressures in the system. And no I don't think it is due to freezing. I have noticed odd slight pressures in low boost situations. In some occasions when boost less than 0.6bar / 8.7psi I’ve noticed minimum registered pressures in the system, which is 0.1bar / 1.5 psi. When I hit the gas pedal for higher boosts, pressure is gone in the system. So I interpret it that on low boost it leaks pressure to the engine somehow… I took the PCV valve under the IC and cleaned it in ultrasonic cleaner to rule out any jamming of it. Still I notice some pressure build up.

I’d see that if it were combustion gasses through rings why it goes away in higher boosts? Or maybe the PCV valve is worn and won’t hold pressure in mild boosts. Boost pressure leaks to engine and is extracted to the front breather under the AC compressor and due to restrictions in AOS can be seen as slight overpressure inside the hose. Or so much blow-by gasses past rings that the pressure goes from front breather and due to restrictions in AOS can be seen as a small pressure in the hose. Front breather valve is closed due to higher pressure in intake manifold. Ouch, wouldn’t want this to be the case. Please help me to diagnose what could cause this?

I assume it leaks boost as since I got this car it has had mixed personality. Eg. sometimes it pulls like mad and sometimes (quite often actually) feels like it is lacking plenty of horses. Haven’t driven other XT’s whether it is feature or an issue.. I’ve done the Danoz fix for clamps though.

Thanks
Have you checked your charge pipe (the long curvey black plastic pipe which links turbo outlet to IC inlet)? For the pre-facelift FXT, it’s been known to crack and leak after a while.
 

·
Registered
2014 Forester XT
Joined
·
48 Posts
Discussion Starter #9
Charge pipe seems to be ok.

Just replaced the PCV valve. After that decided to check whether there is pressure in the engine by removing the oil filler cap. Was amazed how much pulsating air was coming out from the filler hole! Could someone with FA20DIT be so kind and test by removing the filler cap while engine running that is there noticeable air coming?
 
1 - 9 of 9 Posts
Top