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Water-to-air intercooler installation - 81 931
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Sun Jul 25, 2021 12:59 am    Post subject: Reply with quote

I needed to reroute the radiator hose that runs from the intercooler to the hot side of the intercooler radiator. Rather than going all the way to the bottom near the valance, I pulled the line through an opening near the top of the main radiator.

Seemed like an easy thing to do...until I bumped into this box. It just broke off. Apparently this is a mileage counter for the OXS system. After a certain number of miles it's supposed to remind you to change your O2 sensor via red OXS light on the dash.

The part numbers is 477957901C. Some sources indicate that the part is NLA, others indicate they are in stock for around $80. Before trying to find one, I repaired it with the Plastex repair kit (https://www.plastex.net/) I bought a while back. Time will tell if it holds up more than five minutes, but the repair seems solid. The box relies on that point to mount it. Searching through the board, it appears that others have had the same problem. Another option would be to eliminate the box and replace with a ROW speed cable.




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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler
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jacobroufa  



Joined: 18 Nov 2016
Posts: 529
Location: Belvidere, IL

PostPosted: Sun Jul 25, 2021 3:38 am    Post subject: Reply with quote

I had the same issue with this box Chuck, and I tried to keep it whole so I could use the US/OXS two-piece speedo cable.. but mine _still_ broke. ROW speedo cable is the only thing I can do.. I would be happy to send you my OXS counter if you could use it as a (broken, needing similar repair to yours) spare..
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Sun Jul 25, 2021 7:17 am    Post subject: Reply with quote

Me too..
My brown car has a broken box (don’t tighten them!) and also a snapped upper cable, and the 941 has some thing where this box used to be, but doesn’t exactly fit the cables correctly..

I think the solution is to replace with NA cables or ROW cables as has been said, the inner cables are avail online but not the cable housings..

Anyone parting NA cars, we need these cables..

I also need the inner and outer hub clips..

Someone want to start a thread and figure out how we can piece all these things together?

Maybe we can reuse our cable ends and put them on new cable housings? And replace the inner cables with the readily available ones?

I mostly rely on my GPS speedo on my radar detector anyway though.. I find the 924 speedos read quite high.. About 10mph high around 90-100mph actually..
So if you think your cruising 100 on the highway, your probably only really doing 90..
About 6 mph high around 75-85..
And yes my front tires are of correct size, if not even a bit large, so it’s not that..
Speedos are just optimistic I think..
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 2596
Location: MI

PostPosted: Sun Jul 25, 2021 7:22 am    Post subject: Reply with quote

Me too..
My brown car has a broken box (don’t tighten them!) and also a snapped upper cable, and the 941 has some thing where this box used to be, but doesn’t exactly fit the cables correctly..

I think the solution is to replace with NA cables or ROW cables as has been said, the inner cables are avail online but not the cable housings..

Anyone parting NA cars, we need these cables..

I also need the inner and outer hub clips..

Someone want to start a thread and figure out how we can piece all these things together?

Maybe we can reuse our cable ends and put them on new cable housings? And replace the inner cables with the readily available ones?

I mostly rely on my GPS speedo on my radar detector anyway though.. I find the 924 speedos read quite high.. About 10mph high around 90-100mph actually..
So if you think your cruising 100 on the highway, your probably only really doing 90..
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jacobroufa  



Joined: 18 Nov 2016
Posts: 529
Location: Belvidere, IL

PostPosted: Sun Jul 25, 2021 7:33 am    Post subject: Reply with quote

Fasteddie313 wrote:
I find the 924 speedos read quite high.. About 10mph high around 90-100mph actually..
So if you think your cruising 100 on the highway, your probably only really doing 90..
About 6 mph high around 75-85..
And yes my front tires are of correct size, if not even a bit large, so it’s not that..
Speedos are just optimistic I think..


Only have an 85mph speedo, and it definitely reads low. I have smaller profile tires than stock though, so I kind of expect that.. I would think w/ larger tires that might be why you are getting a high reading?

This morning down I90 the traffic was pretty thick..


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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Sun Jul 25, 2021 10:17 pm    Post subject: Reply with quote

jacobroufa wrote:
I had the same issue with this box Chuck, and I tried to keep it whole so I could use the US/OXS two-piece speedo cable.. but mine _still_ broke. ROW speedo cable is the only thing I can do.. I would be happy to send you my OXS counter if you could use it as a (broken, needing similar repair to yours) spare..


Thanks for your kind offer. How about if I let you know if I need it?

I reassembled everything last night, the repair seems to be holding.
Of course the box might grenade once I get the car moving again and hit 20mph.

Doesn’t seem like the best design in terms of how it’s mounted.
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Mike9311  



Joined: 14 Dec 2004
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Location: Chicago-ish

PostPosted: Mon Jul 26, 2021 12:36 am    Post subject: Reply with quote

I'm wondering if something could be printed for this? Even a support cage of some sort
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Mon Jul 26, 2021 8:57 pm    Post subject: Reply with quote

Fasteddie313 wrote:



Are you running enough boost? My car can go much faster than 85mph.
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Mon Jul 26, 2021 8:59 pm    Post subject: Reply with quote

Mike9311 wrote:
I'm wondering if something could be printed for this? Even a support cage of some sort


That's an idea. As I was looking at it, some sort of bracket supporting it from underneath might help. In the interim I wrapped a cable tie around it.
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Mon Jul 26, 2021 9:03 pm    Post subject: Reply with quote

Almost ready to try out the larger intercooler radiator. Still waiting on the main engine fan from Vertex Auto via USPS.

I ran the radiator hose from the hot side of the intercooler down to the intercooler radiator. I also wrapped this hose in heat sleeving. The line runs under the airbox mount to the top of the engine radiator.




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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Mon Jul 26, 2021 9:18 pm    Post subject: Reply with quote

I moved over the small SPAL fan. If it helps I might mount a second fan on the right side to keep things cool while sitting in traffic. As I was mounting the new intercooler radiator I couldn't help but think that something even larger/wider could fit in that space.

The next trick will be to fill the system with distilled water and bleed any air from the system. I'll switch back to 50/50 antifreeze this fall.




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Fasteddie313  



Joined: 29 Sep 2013
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Location: MI

PostPosted: Mon Jul 26, 2021 11:30 pm    Post subject: Reply with quote

Nice nice!!
Is it ready for more test runs?
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Cedric  



Joined: 27 Aug 2004
Posts: 2600
Location: Sweden

PostPosted: Tue Jul 27, 2021 12:25 am    Post subject: Reply with quote

Im glad the up side down mounting worked out well, i think this will be a way more suitable setup, the little fan won't do much but if you will have a big spal main fan that could probably give you some decent airflow through it.
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Thu Jul 29, 2021 10:30 am    Post subject: Reply with quote

chuck21401 wrote:

The driver's side radiator fan worked well...until it didn't. It started making a bad sounding noise and seized up. I removed the fan assembly today. When I turned the fan by hand it sounds like there is a box of rocks in the motor.

I'm wondering if it was mounted upside down. The small fan (which works fine) was on the passenger side and the larger fan on the driver's side.

I'm going to order a new fan rather than buying used; looks like Vertex Auto has them. https://www.vertexauto.com/porsche-924-auxiliary-fan-assembly-p-9912.aspx


A couple of notes about the larger cooling fan that I had to replace. I ordered part 477959455C and received a Bosch fan with part number 0 130 107 077. There is no problem...it fits fine, but the motor is definitely longer...no idea if the specs are any different...it seems to move whole a lot of air. Also, there is only one way to mount these fans in my car...the larger fan is on the driver's side.






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Last edited by chuck21401 on Thu Jul 29, 2021 10:53 am; edited 1 time in total
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chuck21401  



Joined: 20 Feb 2005
Posts: 525
Location: Annapolis, MD

PostPosted: Thu Jul 29, 2021 10:52 am    Post subject: Reply with quote

Fasteddie313 wrote:
Is it ready for more test runs?


I put everything back together Monday night...installed the new cooling fan...mounted the shroud and fans...replaced the air box...etc.

I filled the intercooler water lines with distilled water...slow process to get the air out...but completed that task....no leaks.

Dropped the car down off the ramps....it started right up and pulled it out the garage. By this time it was like 10pm Eastern.

I turned on the headlights ready to go for a drive...heard a strange noise and my hood popped up! I immediately knew what happened...turned off the lights...opened the hood all the way....and removed the relay from the headlight motor.

The hood release cable got caught up in the headlight motor. Ugh. Searching around later I found that this has happened to others. In my case the cable sort of still worked....so I secured the hood and went for a ride.

I drove around to warm up the engine...maybe 10 minutes. Was able to get in a couple of boost runs...seemed to run great....temps from my intake gauge (which isn't the most accurate thing) stayed in the 80s/90s. I can't say that the butt dyno noticed a difference.

At the end of the drive I noticed at the AFR gauge was reading a bit higher when cruising and at idle. Parked the car and went inside. I always park the car for 30 minutes or so before pulling it into the garage. I figure that if it's going to go up in a ball of flames it would be within those 30 minutes.

Thirty minutes later I returned to pull the car into the garage. Turn the key...it cranks but does not start. This happens sometimes...usually I'll try it again...blip the throttle and it comes back to life.

Not this time...it did the same mysterious thing that is has done in the past....it will eventually start and idle for a bit....then idle like its running on three cylinders...the AFR gauge goes completely red (lean) and then it dies. On top of that the stereo behaves oddly. I can turn it on, but when I turn up the volume it shuts down like it's going into a protect mode. It's totally bizarre. Five minutes before that it was running like a scalded cat winding out 3rd gear under full boost.

I'll start another thread for this topic....will need some help troubleshooting.
Also ordered a new hood release cable. Those are cheap. So there's that!
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