Category Archives: 4×4 Sierra CityMörö

My preferred choice of transportation. This really is my everyday car.

X-rings ordered to viscous coupling unit

I visited our local bearing shop at Mansikkala area and they also recommended using X-rings. It seems that the original sealing is kind of square box shape which has a groove on axle facing side that is filled with some sort of foamy stuff. So X-shaped sealing is the closest one generally available product.

Unfortunately they did not had correct size X-ring available and it would have been an order from somewhere longer distance (inside Europe though). They had normal O-ring at that size, but I did not want to take that.

I drove to my favorite hydraulics shop at Kurkvuori area since I knew they also can deliver wide variety of seals and they use a different supplier to order than the bearing shop. It turned out that they were able to order from their supplier X-rings at size I was searching for. The exact size is 5,33 x 46,99mm and I agreed that they will take those when they do their next order to their supplier so I will save shipment costs. So probably X-rings arrive at the end of next week, but I’m not able to fetch them until the week after that due some coming travels. Hopefully the ordered seals will fit to my need, but that we shall see later.

Before the seals arrive I can dismantle the gearbox I taken out from my Sierra at the beginning of 2013 when I replaced also the engine. That gearbox is perfectly OK other vice, but it has also viscous coupling unit surrendered. So I will put this refurbished unit inside that gearbox and I have another faulty spare viscous coupling unit to refurbish sometime later when I have tested does this work as expected or not. 🙂

Choosing the silicone oil

Some years ago I studied this topic a little bit and came to a conclusion that I will use 60000 cSt silicone oils in my Sierra’s center viscous coupling unit. Today I did some Googling and tried to verify do I still agree with the outcome. It seems to be as hard as earlier to find proper facts about this. So I will use the stuff I ordered some years ago:


This fluid is meant to small RC cars, but based some real life tests by the others it seems to do it’s job quite well. I expect that I need to consume 2,5 bottles until the viscous coupling unit is full, but we will see that later.  There are different viscosity fluids available for RC cars ranging from some hundred cSt to 500000 cSt. By what some UK forums are saying you should not use more than max 300000 cSt fluids and there are some bad examples what happens with too thick syrups.

By current knowledge I have I’d say 50000-100000 cSt is the optimal range for normal use car, but people seem to have achieved some good results also with 12500 cSt Scania viscous fan fluids (561072). So beats me what should be used since this seem to be a secret science, but my choice has been made and I’ll use 60000 cSt. Unfortunately it most probably will take quite long time until I’m actually testing how this is working since this is my spare viscous coupling unit I’m working with. And in my car I have a brand new (bought some years ago) Sierra Cosworth viscous coupling unit installed at the beginning of 2013.

Wikipedia article about viscosity:

I also managed to find some specs about the sealings and seems that they should be X shaped O-rings XR 5.33×47.00mm. People seem to have also used standard O-rings with good results, but I think having original like sealing with double contacting surfaces should be much better. But let’s see when I visit local bearing shop with the parts and old rings since they usually are able to give really good hints.


Spare viscous coupling unit dismantled

I finished dismantling my spare viscous coupling unit and preliminary cleaning of the parts. Both sealings were totally end of their life and seems that some plates have been rather hot. But based on my understanding those parts turned to blue because of oil and hot conditions should be perfectly ok to reuse. Next thing is to find new sealings and start assembling it back to one piece.



4×4 Sierra CityMörö album from Facebook

“This is a photo gallery of my every day car. The philosophy for this project is not to create a show piece “bling mobile”, but to do everything as good as possible and cost efficient way. The expected end result should be something quite different compared to what most tune-up car builders are doing. :-)”

From 4×4 Sierra CityMörö, posted by Sami Sipponen on 5/10/2010 (190 items)

Generated by Facebook Photo Fetcher 2

A bit different subwoofer project album from Facebook

“Let’s create something different and crazy ;-)”

From Project “a bit different subwoofer”, posted by Sami Sipponen on 5/23/2013 (28 items)

Generated by Facebook Photo Fetcher 2

Sierra instrumentation illumination led modification

This page shows you an example how to mod Ford Sierra’s instrumentation illumination with the blue leds. First I bought 5mm blue leds and 470ohm resistors from Bebek. You can calculate resistor values by yourself easily with LedCalc. There are six lightbulbs at Sierra’s speedo, temp, fuel gauge, etc. instrument cluster.

Here you can see ready cutted leds and resistors:

As you probably can see I sanded the top of the leds to divide the light better. If you don’t sand the top of the leds rough you will probably get nasty bright spots to your instrumentation illumination. Here are a couple of images about the manufacturing process:

Please remember to cool down the leds before you put the power on… Leds are very sensitive to too much heat and they will dim very fast if powered up while they are too hot. Also remember to connect plus and minus sides correctly because the leds won’t lit up if +/- are not correctly connected. Leds are able to whitstand short tests with incorrect +/- connections, but it is recommended to avoid this.

Here is the end result:

As you can see there are some brighter spots and dimmer spots… I’ll try to smooth the light somehow later, but let’s see. It could be a good idea to mount the leds deeper inside the plastic holders, but I haven’t yet tested this.

It seems also a littlebit dimmer than original lightning, but it is still bright enough. The problem with the brightness is probably related to the green color filters at the back of the instrumentation backgrounds. Sadly it seems that those color filters cannot be removed without damaging the background panels.

However this project will continue with the following illumination modifications: push buttons, clock, cigarette lighter, etc.. I will modify all the light sources with leds, so later we will see how I succeed…



UPDATE 23.12.2008

I removed the square shaped green color filters from speedometers mileage display: (filters still in place at this image)

After that I also grinded the top of the leds flat (sorry, but I don’t have a picture of the flattened leds at the moment). After these modifications the end result is:

A little better than earlier, but still some work to do… Luckily I have some ideas to try. 🙂

Here are two pictures of unmodified instrumentation cluster: