Oil Pressure Gauge - Change to Mechanical Advice, Parts List and Result

[brianjhall31]

I, like many on these forums, had been concerned over the accuracy of the original Oil Pressure Gauge and Sender on my 2003 K Series R300 SV.  Looking at the results that others had experienced, and with some very helpful advice from member Brian Deacon, I have just completed the installation of a Mechanical Gauge and connection pipework. I took note that others advise additionally using "Goodridge" stainless braided brake hose rather than the plastic tube that comes with the Gauge owing to the Caterham installation being very exposed to FOD and its better resistance to kinking/chaffing etc.

Apart from the selection of the actual Gauge I spent the most time in establishing the best routing for the pipework as this was critical given the Goodridge Hose would be made to order.  I also made some tests with similar sized hose to establish if I could route it through the large grommet in the transmission tunnel forward of the gear lever as, in my case, this already had the main dashboard loom and battery cut off switch cables running through it.  Fortunately, with a liberal application of Vaseline and a little warmth, it could be done (otherwise it would have meant cutting a new hole and routing elsewhere)

I used some spare 1.5mm 3 core round electric cable to map out the best routing bearing in mind the use of existing points of attachment and security.  I then cut this to the length required for the Goodridge Hose.

All the items were supplied by Merlin Motorsport at Castle Combe.  The Goodridge Hose was made will I waited (5 mins)

Here is the complete list of parts:

Goodridge PTFE Stainless Steel Brake Hose G-600-03 = 21.96 (price depends on hose length required @ 1.22 per 10cm)

Goodridge Straight Gauge Fitting G-GA-3 x 1 = 2.83

Goodridge -3JIC/3/8 UNF Straight G-6001-03P x 1 = 8.03

Goodridge 1/8 BSP Straight Female G-321-03P x 1 = 10.68

Adaptor M12X1.5 x 1/8 BSP (MM) ADP-M12X15 x 1 = 4.78

Stack Mechanical Oil Pressure Gauge ST3102 x 1 = 42.00 (personal choice as to Bar or PSI, sweep range and manaufacturer)

Copper Folded Washer M12 M-COP-M12 x 1 = 0.42 (essential to avoid oil leak between engine mount and M12X1.5 Adaptor)

Total inc VAT = £108.85

Readings (normal operating temp) with original Gauge and Sender were showing 3 Bar at 3000 RPM and 1.5 Bar at 1000 RPM

Readings (normal operating temp) with Mechanical Gauge are now showing 70 PSI (4.8 Bar) and 40 PSI (2.7 Bar) respectively.

Conclusion:  Task it not difficult.  In my case with the Stack Gauge the existing loom's lighting circuit female spade connectors (12v and Grd) fitted straight on with no modification and a routing for the pipework can be easily established from the current Pressure Sender mount on the engine, L to R across the front of the Sump (using the existing Loom mountings), back down the RH side of the engine and up onto the diagonal Chassis Tube under the induction manifold.  From here back along the tube into the transmission tunnel and up the the existing grommet.  More important - I am now much happier that I have the correct and reliable Oil Pressure Information!

 

[Golf Juliet Tango]

I would put a mechanical oil pressure gauge into the 21 if I could retain the Caterham face on the display. 

 

[Golf Juliet Tango]

I received a message:

Have you asked John Ostick if he could do precisely that?
He's "JDO", independent, and very helpful.
https://www.lotus7.club/forum/techtalk/speedometer-and-instrument-repairs
I see it as two tasks that have to be solved:
The skill to break down and reassemble the gauges, and that's what he does all day.
Finding the bits that give the right sweep from the new mechanical internals across the old face. I don't know if such a combination exists... but he's the first person I'd turn to to find out. :-)

 It's certainly an option, thank you - you should post these helpful suggestions publicly.  It does sound like an expensive option but one worth investigating.  I doubt there is much need to rework the internals; they exist on one gauge and the face exists on the other.  The Caterham branded gauge is sufficiently vague, so once a user knows where the needle should be pointing, they can just remember the optimum position.

[Golf Juliet Tango]

Looking at http://www.jdo1.com/faq_page.html

Q:  Do you repair ‘Dual gauges’ including ‘Capillary units’ ?

A:  Sorry no... Please see ‘other services page’   ( which includes a link for ‘NEW UNITS’ )

 The other services page has "no capillary instruments" in red and emboldened.  Which I think would rule out mechanical Oil pressure gauges, sadly.

[SLR No.77]

All the Caterham gauges are electric and have approximately a 90 degree sweep of the needle whereas mechanical gauges have a 270 degree sweep. Unless the a 270 deg dial face is recreated from scratch with the Caterham logo you're not going to achieve what you need.

Stu.

[Golf Juliet Tango]

Thanks Stu.  I didn't realise the sweep would be so big.  I'll bin that idea.  I wouldn't deface the interior of the 21 any more (i have put in a micro toggle switch for coolant/oil temperature)

[Mechanical Moz]

https://www.demon-tweeks.com/uk/smiths-telemetrix-mechanical-oil-pressure-gauge-270878/

As it is a Smiths gauge it may be possible for Caerbont to build one using the Caterham face.

[CharlesElliott]

I think I'm about the only one that really doesn't see the point in mechanical gauges. They add a tube that can contain pressurised oil into the cabin, and I've seem multiple examples of tubes coming loose or being cut resulting in oil leaks. A decent electronic gauge is far better in my view - just because the sender Caterham used on the K series is not of good quality and in a very exposed place, it shouldn't mean that electronic gauges are rejected as a poor option.

[John Vine]

I think one significant advantage of the mechanical gauge is speed of response.  The electronic gauges tend to be heavily damped.

I fitted one to my 1.8K to improve reliability, but I went down the mechanical route on my R400D after reading scare stories about fluctuating oil pressure on wet-sump cars like mine.

JV

[CharlesElliott]

That may be true in general, but my Spa digital gauge would update instantaneously, and I also logged data from it for later viewing. I posted a thread with details and pictures in the past....unfortunately the pictures were lost in the migration (see https://www.lotus7.club/forum/techtalk/updated-k-series-oil-pressure-data-racecar-added-video)

[John Vine]

Interesting!  Is there any chance you could repair those broken links?  I'd love to see the plots.

Re damping, Caerbont have told me that they can alter the damping on standard CC gauges, but to what extent they didn't say.  I'm assuming the standard gauges are analogue rather than digital?  If so, is it the digital bit that gives the SPA gauges an instantaneous response?

JV

[Golf Juliet Tango]

Charles

Quite right and I wouldn't dream of replacing the system in my Crossflow.

It is a very specific problem to the K Series and its installation in Caterhams (7s and 21s - well my 21). All sorts of ingenuity has been shown in addressing the problem. It appears that none provides a reliable solution.

Catrham Cars wouldn't face the issue when it was relevant to them; it is no longer their problem, it remains an owners' problem.

I have given up, I check there is sufficient oil and just drive.

[brianjhall31]

I hope my modification will prove to be "reliable".  I admit there is now a pipe with pressurized oil coming through into the cockpit area but, by using the Goodridge Brake hose and its specified connectors, I believe it is secure as possible.

The major factor is having an indicated Engine Oil Pressure that I am confident is accurate, otherwise you could just have a warning light saying pressure exists (or not!)

If you are going to the expense to have a gauge it might as well be accurate.  From an economic point of view a system using a high quality (reliable info) electronic sender and gauge is more expensive than the mechanical solution.   

[John Vine]

Catrham Cars wouldn't face the issue when it was relevant to them...

I don't think that's entirely true.  CC's response was to introduce the remote-sender kit.  This had two advantages: it placed the sender in a much less vulnerable location, and it much reduced the effect of engine vibration.

JV 

[7 wonders of the world]

JV,

thats true form a durability point as the do object to the torrent or vibrations emitted by our cars, however the limited scale and damping on the OE gauge makes it pretty useless, having run a wet sump Duratec and seen the difference between the OE and a full scale mechanical gauge the oil pressure fluctuations are significant and frightening....especially on long fast left handers

I even went for a blat with a fellow member watching the gauge for me... 

Dry sump on my current one....

Seen several wet sumped Duratec engines all with toasted big end shells....

[StevehS3]

I have had mechanical and currently have an original gauge. Whilst there is no denying I have more confidence in mechanical I find the remotely mounted OE sender and gauge reliable (so far!) and fit for purpose. I haven’t ever looked at mine going through bends on track and I don’t know what the exact pressure is supposed to be for given engine temperatures. If I do suffer a short duration loss of pressure whilst cornering there isn’t anything I would do about it anyway and perhaps they all do that with my setup. I kind of have a feel for what normal is on the gauge for various conditions and think I would know if something was wrong or had changed.

[7 wonders of the world]

you will now somethings wrong when the bottom end expires, personally I prefer the prevention rather than cure approach....

[SLR No.77]

The 270 degree needle sweep is good enough reason to go mechanical ... and yes having had the bottom end expire on track I'm acutely aware of the having a gauge that is accurate and readable. 

Stu.

[John Vine]

...the oil pressure fluctuations are significant and frightening...

And it was thanks to your advice that I fitted a mechanical gauge on my wet-sump R400D.  I'm glad I did -- so much more reassuring to see what's actually happening second by second, although I've yet to observe the wild OP fluctuations you reported.

JV

[Golf Juliet Tango]

JV

Sorry, I had overlooked that, probably I never saw it.  On the 21 mt sensor is mounted on the end of a length of flexible braided hose, to get it higher and make it better protected; still failed.

[StevehS3]

Is it left hand bends that cause oil pressure drops on the K Series?

[7 wonders of the world]

Sorry JV, forgot we spoke about that many moons ago  

SteveS3 - the long left handers applies to Duratec wet sumped engines.

[John Vine]

On the 21 mt sensor is mounted on the end of a length of flexible braided hose, to get it higher and make it better protected; still failed.

Now that's intriguing as it sounds as though your 21 already has CC's remote-sender kit.  Do you happen to know how long the sender lasted in that location before it succumbed?

JV   

[Golf Juliet Tango]

Months.  But "failed" might be inaccurate, it misreads in as much as it doesn't give an accurate reading, judged against tests conducted with a mechanical gauge.

I think Rob made the hose up rather than using an official kit.

[Rich Goddard]

I know there’re a few threads on this but picked this one as fairly representative. 
See my review below posted on Trustpilot after a disappointing experience with the DT kit. Hope it helps someone gather the other parts together if you’re committing to the DT kit.