ECU air duct, is it required?

[eriscentro]

This afternoon, I happened to see the inside of an 96 854's (NA) hood here on the site and it occurred to me that I don't have an air duct attached to my ECU leading to the radiator area. Instead, the hole simply leads to the engine bay. Under my ownership of the car, I've never had it, and I believe that neither did my father when he bought the car used in 2008. Is this duct actually important? Given that it's been driven for years without it, I'm doubting it's importance.

[Glencoeteen]

do you absolutely need it..
no but its nice to help keep the brain of the car cool, if you were like me with a Tuned T5 then absolutely i like to keep it as cool as i can rather than risk it getting too hot.

Take a laptop computer it gets hot when you use it a lot, different programs etc with out the cooling fan it would melt/ short out, some could theoretically catch fire, anything is possible, but keep in mind due to heat and lack of cooling air flow it can potentially lead to problems for some, IPD has the hose for a bank breaking $8.18

[polskamafia mjl]

I agree, its cheap enough that there's really no reason not to have one.

[Atis]

The ECUs are designed to withstand their required lifetime (e.g. 15 years and 300000 km). It could be, that without that plastic tube, the ECU will not get that hot to fry itself, but increases the thermal load on it, which will decrease its lifetime. It could be as well, that there is thermocouple on the PCB and it measures the temperature of the ECU and if it gets too hot, it switches on the fan.
So, I would just buy a new airduct in your case.

By the way, is there anyone who checked where that heat insulated hose goes from the bottom of ECU box?

[abscate]

On my 1999 it goes into the firewall port which then connects into the climate system. Interestingly it is before the heater core so it's only a cooling function supplied by this hose.

[Atis]

I am wondering, whether the engine cooling fan should suck air from the passanger compartment or the climate blower should blow fresh air through the ECU box...

[j-dawg]

On my 1999 it goes into the firewall port which then connects into the climate system. Interestingly it is before the heater core so it's only a cooling function supplied by this hose.

really? on my 99 the duct goes to the radiator area, just like on the older cars.

[abscate]

Duct to the radiator from front of ECU box.

Insulated duct from rear of ECU box goes back to the climate system.

[nferi93]

I'm not sure, but I guess it's for the airmix function

[Ben850]

I wanted to remind this applicable thread.

https://www.matthewsvolvosite.com/forums ... ECU+filter