Engine bay fan issue

PJP · 2 Dec 2018

Hi, I have a 2008 a Gen 1, 3.8 cab.

I have had this issue since buying the car Spring 2017.

I start it, let it warm up then drive it. when I drive for any length of time say above 15 minutes, any time of year including today (7 deg C). I get where I'm going, no fan on, park, turn the engine off, still no fan on, leave the car 5 minutes or an hour, as soon as I start the car the fans on, it doesn't then ever go off even if I drive an hour. My Indi says he can't find a fault, it seems as though the heat sync from the engine fills the bay with hot air thus triggering the sensor but I assumed it would just go off after the fan has done its job. With the roof down the noise bugs me, no other issue.

Sensor was changed earlier in the year.

Any thoughts welcome

Jam911 · 2 Dec 2018

I know it sounds obvious but have to checked to see that both of the fans are not jammed with a small stone or other obstruction.

PJP · 2 Dec 2018

Thanks but it's the engine bay electric fan situated in the engine bay lid.

FZP · 2 Dec 2018

Perhaps there is something in the below that might give you some ideas on where the issue lies.

It happened to me from time to time last year and last week it came back: the fan was basically on blowing hard from the moment I was starting the car and maybe around 1 hour after leaving the car.

Here's what I did and worked for me:
- I had some Durametric: error code was P1157 "sensor engine compartment, value too low"
- I checked that the sensor was in its proper spot (and not falling in the engine compartment bay where it would connect directly with the hot metal parts), which was the case; I simply replaced the rubber joint anyway. Fan still blowing hard.
- I tested the relay D5 (DME that controls the engine fan) : it was working fine. When you take it off the fan stops, when you put it back, the fan blowing resumes.

So: tested and working. Fan still blowing hard.
- I then moved on to the sensor itself and was now suspecting the manometer. I swiched mine for another one I had, and each time the manometer was installed the fan blowing resumed. So it was not the manometer... Fan still blowing hard.
- I then noticed that the 2 small cables connecting the sensor to the "engine bay" was sectionned. So I had some welding and taping done. Fan not blowing anymore.

So it was a simple repair actually, without having to change any relay or even the fan itself.
Worst case scenario would be having to change both the fan ($100) and the expensive calculator ($700-1000)...

PJP · 2 Dec 2018

Thanks FZP, I will take a look, it would be great to resolve the problem

deMort · 2 Dec 2018

The engine bay fan is activated by the engine temp air sensor .. its located on the o/s/r inlet mainifold ..

When the temp of the bay gets too high it will switch the fan on .

The usual fault is if the sensor becomes detatched .. if its in place then i would expect the car is doing what it was designed to do ..

I have never in 15 years had to replace this sensor .

I can tell you there was a campaign many years ago where we removed the fuse for stage one of this fan and fitted a blanking plug.

Stage one and the fan would run all the time which resulted in the motor burning out .

If you think about it .. a hot engine and car sitting for a bit will build up latent heat .. hence the fan will trigger .

From what you have descripbed then im not sure there is a problem but i will suggest you or a garage looks at the temp on the actual values on a tester just to confirm its correct .

As i understand it then once the fan is triggered it will pretty much run untill you cycle the ignition .. but i am unsure of this .. its just from my observations over the years .

PJP · 2 Dec 2018

Thanks DeMort, my Indie says there's nothing wrong, but I will also take a look at the sensor position. I agree that it must be the heat from engine bringing it on but I just assumed it would go off reasonably quickly. It does only go off after I let the engine cool for a few hours. It's due there again in Feb/March so will also ask them to do the diagnostic you sugggest

Thanks for the advice from all

taffybloke · 2 Dec 2018

I had the same issue as deMort mentioned, My engine bay fan would run soon after the engine was warm and would stay on long after the car was switched off. The sensor that is located on the right bank inlet manifold had come loose and was resting on the engine. The grommet holding the sensor in place was missing so I ordered a replacement and have had no issues since.

Mike

Engine bay fan issue

PJP

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Jam911

Albert Park

PJP

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FZP

Zandvoort

PJP

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deMort

Monaco

PJP

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taffybloke

Silverstone

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