Embarrassing which fill hole?

[John Vine]

Plan is to provide one which fits under the nose cone.

If Derek succeeds, the inference is that these race rads are manufactured with significant variations in dimensions and tolerances.  Alternatively, of course, it could be that the nosecones themselves vary in a similar way. 

Along with others, I'm on the edge of my seat awaiting the verdict!

JV 

[CtrMint]

I'm still waiting to hear from him, I too am eager to understand how this gets resolved.  Since taking the decision to SVA here on the Isle of Man rather than IVA in the UK it means CC must resolve the issue remotely. The car will go for a PBS immediately after it is registered but more for setup than compliance. 

[SM25T]

That's a novel design idea .... a radiator which fits under the bodywork without fouling anything. This could change the world.

[John Vine]

Since taking the decision to SVA here on the Isle of Man rather than IVA in the UK...

Do you know what standards a local SVA test site works to?  I ask as they may not be so picky about (or even need) all the extra bits of trim, bolt covers and the like that IVA demands, which could save you quite a lot of work.  All the builders I know (myself included) tend to ditch all these bits anyway once they have the necessary pass certificate.  And none of it is needed for the MOT. (Do you have a similar MOT in the IoM?)

JV

 

[CtrMint]

John,

First up, no MOT.

I'm building the car to the same standard as an IVA, and assuming it will pass as a result, with the exception of that first grommet on the headlight bracket. I personally don't mind the IVA trim around some of the apertures so will be happy to keep. I'll also test the car without the weather gear attached.

I am kinda assuming its shorter since it takes approximately 1 hour rather than 3 hours as per the IVA.

At the moment I have a degree of positivity about completing the build. I have very little to do, but the items remaining are just problematic, they include.

1. Radiator/oil cooler
2. Headlight bracket and wiring
3. Roll bar (possible)

Oustanding items are

1. Rear wings plus lights
2. Rear suspension struts
3. Front cycle wings
4. Speed sensor --- new post coming I'm afraid
5. Wing mirrors

The roll bar may or may not be an issue, the original didn't fit, Derek has sent another but its stuck at the in-laws awaiting pickup.  Hopefully the replacement will fit otherwise, well I hate to think what will happen then.  The bolts holes on the roll bar base next the suspension were out by about 3mm-4mm!

 

 

[CtrMint]

Duplicate

[John Vine]

At the moment I have a degree of positivity about completing the build.

That was becoming apparent from your recent posts.  I'm sure we're all delighted to hear that!

Speed sensor --- new post coming I'm afraid

Loads of advice and tips available here and in the archives.

As Churchill famously said: "Keep buggering on!"

JV

[kiloromeo]

Hi CtrMint - thought I'd follow this one up with a comment, I've been reading about your experiences. I'm a little behind you in a build of a 270S, much simpler cooling, the current 1.1 manual seems to be designed for the 1.6 Sigma and is quite good in some respects, but short on description. I'm having all the same minor issues you are having. Thank goodness for all the kind and knowledgeable people who have offered their advice, and others who have blogged their experiences so we have a reference that it is usual and not just us!

The manual states fill diff with 0.8L of oil (std diff). I filled it with all of the 1L supplied as I expected it to overflow out of the fill hole. It all went in, didn't overflow, and when I queried this, the reply was no more needed ( and presumably 0.2L does not need to come out). So whats the 0.8L figure all about ! Not sure about this one.

I persevered with the headlights. In the end to get the headlight bracket to mate with the car, I took off the grommet exiting the bracket as it can't be seen when on the car.

 

[CtrMint]

Hey Kiloromeo,

Thanks for contributing to the thread, and I would love to see some pics on your progress.  I totally agree with you regarding the support from the BC, I think I would have failed some time ago.

I found the "ikea" manual as pretty unreliable for anything other than the chassis, even Derek at CC told me to only use it for the chassis.  I think for me the main problem is that it doesn't even acknowledge the 420, including the cooling and dry sump system.  As a result, I wouldn't put too much stock in for the volume of oil needed for the LSD either. 

With regards the grommet, have you installed the grommet where the wiring enters into the headlight tube, just under the indicator, its that one which has caused me so much grief.

 

[kiloromeo]

I've taken some pics, mainly as evidence of parts, and management has taken some of me holding a torque wrench etc for the IVA people, but that's about it. I'll see if there's anything interesting and post.

Re the grommet on the angled hole in the tube - impossible, so I cut one in half (lengthwise, leaving a short T rather than an H ), manipulated it in, then used some quick drying superglue. It looks ok and hopefully will stay in place. Must say I would not like to do it again!

The b*stard for me was getting the assembly on to the car, hence my comment about omitting the grommet at the end of the bracket. Also had to open up the metal tang a little to get that to catch. There is a grommet I fitted on the car mount, so the wires pass through that into the engine bay ok.

[mikecocker]

When the current design of backplate/diff carrier was introduced at the end of 2013, a workshop notice was sent out for those retrofitting the kit, which stated;

Fill with 800 ml of oil

Do not use fill hole as level

On the exploded diagram, the plug is described as fill/drain.

 

[ScottR400D]

That’s interesting Mike, anyone got any idea where that notice might be found?

i have no recollection of anything like that when I built my R400 in 2015. I’ve always filled it to the level hole, and not had any problems so far. My handbook says 1.2 litres for the diff, which is to the level hole.

I am aware of some owners suffering leaks around the drive shafts, maybe a reduced oil level was a misguided attempt to stop that?

Maybe later diff covers have the fill/level hole in a different place? Not unreasonable to assume that you fill to the fill/level hole, surely? 

it also seems that some of these diffs are sent out filled, others empty, though that might be a related to LSD and non LSD?

Does anyone know for sure? 

It seems that, not unusually for CC, that there have been different ‘recommendations’  over the years more based on reactive trial and error than sound engineering. 

[Jonathan Kay]

It's Workshop Notice 542. I don't have a copy and would appreciate one for the library.

Previous discussions:

• https://www.lotus7.club/forum/techtalk/diff-leak-2, with the picture
• https://www.lotus7.club/forum/techtalk/bmw-differential-have-you-had-oil-leaks-output-seals

Jonathan

[CtrMint]

Sorry Guys, to be clear are you saying the LSD fitted to my 420 needs 0.8l and not 1l?

If so I guess I can extract 200ml with a syringe 

[ScottR400D]

I don’t think anyone truly knows, CtrMint. 

Having re-read the threads that JK linked to, and to which I contributed, it’s pretty clear that there are no definite conditions to ensure no leaks or for that matter, leaks. 

Undoubtedly there are diffs with 1.2L in not leaking and diffs with .8L that are still leaking. 

I notice that the oil you have used (supplied with the kit?) is of a higher viscosity than that  which CC used to supply and recommend. Maybe yet another suck it and see attempt to solve an issue they really don’t understand? 

[CtrMint]

"Suck it and see" are they really that bad.

Well based on that bobbin too...

 

[aerobod - near CYYC]

There are a couple of things that I think are important to minimize, if not eliminate the BMW diff oil leaks:

- Ensure that the seals are absolutely flush with the diff casing flanges they are mounted in, as they can be pushed further in, but the shoulder on the driveshaft may not then always sit within the seal if there is any lateral movement of the driveshaft under hard use.

- The diff has to be absolutely centred between the hubs, using the supplied shims on the long top mounting bolt to adjust the lateral position.

With my 2012 R400D I had to replace the driveshaft seals when I rebuilt the diff to install the thicker shims inside the Titan LSD that Caterham provided to reduce clunking along with the upgraded rear cover to eliminate the deDion tube contact. I ensured that the seals were square and flush with the flange face by using a flat aluminium block that spanned across the flange to seat the seal, as the E46 I had with the same diff in the past had the seals installed that way. That was about 25,000km ago and my diff has been filled with 1.2 litres or so to the bottom of the fill hole. I don’t have any leaks and the car has done 8 hard track days and many autocross events with most track use being on slick tyres.

[Jim 123]

I do know that BMW have issued Service Instructions on their diffs to reduce the originally specified fill level to eliminate leaks.

[Geoff Brown]

aerobod (post # 42) - When I replaced my BMW LSD out put seals I installed them as far as they would go into the casing.

At the time the car was three years & four months on the road. Changed the seals November 2016 @13160 miles. Now at 18,500 - no leaks yet & Diff filled to overflowing. I am waiting for the three year, four month point again before making further comment !

I understand your explanation of the shoulder on the drive shafts may abut the seal lips but after measuring I installed them all the way in. Plus I carefully polished out the existing seal wear rim with crocus paper. 

[aerobod - near CYYC]

If you don’t get much lateral movement of the diff due to flex of the metalastic bushes, significant suspension bush flex, or flex of the chassis, you will probably be OK without the extra 5mm or so of margin having the seals flush with the case will give. I’m not sure why BMW designed it that way, perhaps they had a wider seal at some point. Most BMW diffed Caterhams were also fine from the point of view of not needing the rear cover upgrade, but hard use would cause enough bush and chassis flex that the cover bolts would leave marks on the deDion tube due to the diff moving relative to the other components (as I found with my R400D).