Fastback's cars.

[Fastback]

Thanks for the reply.

Don't believe too much pressure, viz; got it sorted, regassed, was working, gas leaks out as evidenced by UV residue, now at three quarters and not working. Regas to just into green, still not working. Therefore not too much pressure, reasonable logic?

I was wondering if the chap who worked on it may have dislodged an electrical connector somewhere or maybe a faulty clutch on the compressor?

[scoobyh123]

Thanks for the reply.

Don't believe too much pressure, viz; got it sorted, regassed, was working, gas leaks out as evidenced by UV residue, now at three quarters and not working. Regas to just into green, still not working. Therefore not too much pressure, reasonable logic?

I was wondering if the chap who worked on it may have dislodged an electrical connector somewhere or maybe a faulty clutch on the compressor?

Definitely reasonable logic, yes. When you say "just into the green", does it show any numbers for the pressure at all? Also how accurate is the pressure gauge you're using?

You can test the compressor clutch by finding the feed to it, disconnecting it and making a test lead to plug into it. Usually it's a normal push-on/Lucar/spade 1/4" terminal hidden inside the plug so a crimp for that (can't remember which is male and which is female in the connectors), a length of wire bared at the other end so you can connect the test wire onto the clutch feed and dab it onto the +ve terminal of the battery. Do this with the engine running and you should get a tiny splash of current as the wire touches the battery and hear the clunk of the clutch engaging and hear the compressor start turning.

Don't keep it running like this as if it's low on gas, firstly the compressor will be working too hard, secondly it may also be low on oil and thirdly you're not in the car enjoying the cool.

I'm wondering if you're just below the thrshold of how much it needs to start, past few days have been warm so low side pressure will be inherently higher but maybe still not enough to trigger the trinary switch.

That could be your next port of call in diagnostic testing. I'd need to look up the wiring on it but if it's a simple two terminal switch (can't remember just now if they're 2 or 3 terminal on the 800s) make a link wire to link the switch and try the AC then. If it works, refit the trinary switch connector to the switch then try adding a little more gas with the AC switched on (but obviously not running because the trinary switch is saying low pressure), coldest temp selected and vents for the outlet, blower on full.
With the engine running and everything set as described, add a little more gas at a time to see if there's a certain point where it will come back to life. I've found this with my Sterling and the DIY top up i used for that. Usually it needs to be in the higher end of the geren, almost into the next sector that "suggests" too much pressure - i've come to the conclusion the gauge isn't greatly accurate!

[Fastback]

Thanks Dave.

No numbers, just sections marked. It is the STP trigger guage (non digital) and obviously I don't know how precise it is, save to say it's worked before. Didn't want to over fill system (gas is expensive), so did err on the side of caution. Maybe a bit more would kick it in to life?

Give me a few days to follow those instructions.

[scoobyh123]

That would be this one then Mark?

https://www.halfords.com/motoring/engin ... 61419.html

Pretty certain that's the same as mine but i've had mine several years and think it has number on the scale as well, i'll have a look in a bit.

I really need to try and change the clutch bearing on my compressor but that's a lot easier said than done, i just use the AC sparingly at the moment so i don't deafen pedestrians three counties away!

[scoobyh123]

Some pics of the gauge on mine which is also the STP Easy Chill :







I'm pretty certain mine needed ~55psi to shut the Low Pressure (LP) switch so the compressor kicked in, that was on a reasonably cool day (~15C) and looking at some of the proper gauges online, moving up to the ambient temperature of 20C it's nearer 70psi :



The outer markings are pressure, the inner ones temperature for the different gases, ours is R134a so if you look at the pressures Vs temperatures (ambient) you should see what i'm referring to.

Obviously with the right kit to fully discharge the system then refill the exact amount you don't need to do all this but that kit comes £Expensive-OUCH!

[Fastback]

The time has come to get new rubber on the Sterling. Now the controversial question is, what size? I have 16" rims on the car which I believe were fitted to the KV6 Coupe as standard (fingers, not Prestige). That tyre, as stated in the owner handbook is 205/55/16. However, I chose to run 205/60/16. There is the speed/torque payoff but what of rolling radius and speedo accuracy? Going 55 means more rotations per mile (786 vs 811) but 60 closely matches the original 195/65/15 revs per mile of 808.

Also the cost of the 60 profile is £27 more per tyre (Goodyear EfficientGrip 2, Blackcircles), more than half as much again. That's 2 for the price of 3!

Finally, what tyre pressures, particularly if I stay with the 60 profile?

[scoobyh123]

Running 205/60/16 gives a diameter of 652.4mm Mark. The 205/55/16 gives 631.9mm. Using 195/65/15 as a base point is 634.5mm.

https://www.willtheyfit.com/index.php?w ... offset2=10

That means using 205/60/16 is nearly 20mm bigger in diameter! That's gives just under 3% error on the speedo so if your speedo is currently accurate at 60mph, fitting 205/60/16 tyres will (in theory) give 61.8mph which might make the difference between a speeding fine and not.

There are loads of apps you can download for GPS speedo on your phone, don't forget that if your current tyres are worn down to the leagal limit, they've lost ~13mm in diameter as well - new tyres have 8mm tread depth, the legal limit is 1.6mm so 6.4mm worn off the tread equates to 12.8mm overall. Also worth trying :

https://www.tyreleader.co.uk/

As far as i'm aware, they are a true independent and not owned by one of the big manufacturers (blackcircles is owned by one of the big ones but can't remember which) so you should have more choice and probably better prices.

On 205/55/16 the pressure is 32psi all round. Whatever tyres you get i would suggest using that as a starting point.

[Fastback]

Even with the 205/60/16 the speedo still reads faster than actual. About 74mph on the clock is a measured GPS 70 mph. 55 profile tyres are even further out from previous experience. To maintain the same velocity with a 55 profile I would need more engine speed, using more fuel?

32 psi all round is under max load conditions (coupe) according to my 96MY owners handbook, normal driving 28F/32R for 205/55/16. Interestingly it also says Sterling (presumably 15") 28F/26R.

Had a look at Tyreleader, thanks; looking more expensive than Blackcircles (if fitting is extra) and a surprising lack of fitters in my area. I'll probably stick with the 60 profile because it is now what I know and like. I would just like some sort of tyre pressure guidance; should you increase or decrease with larger tyres?

[scoobyh123]

You need to check the tyre size against the pressures Mark, not the model :



Admittedly that's from the Mk2a WSM but i can't get RAVE to open for some unknown reason at the moment. However tyre pressures didn't change that much.

If your speedo is reading ~5% fast on 205/60/16s, assuming they're not worn then it will probably read about 8-10% fast on 205/55/16s.

The speedo in my Volvo reads ~8% fast even with 195/65/15s on (original fit was 185/60/15 or 185/65/15) and some bright spark has discovered a calibration resistor in the speedo that tends to go high after time causing a high reading on the speedo. I keep thinking about fitting a new resistor in place of the old one but to be honest it's not worth the grief. On the original size tyres it read ~12% fast so i understand where you're coming from on the 205/60/16s - i've calculated if i fitted 205/70/15s to my Volvo the speedo would be accurate but the price of those tyres is £OUCH and definitely prohibitive!

[Fastback]

That WSM data is interesting, completely different from the later handbook. The guides are different for the Coupe vs other models presumably because they either had the 17" (2.0 Vitesse) or the unique 16" on the 2.5. So as such, with the right tyres, 28F/32R is correct and I guess that's a start point if I stay with the 60 profile, maybe a touch more.

I did once fit 205/65/16 and that gave a precise speedo reading. However they caught even before full lock, so they had to go fairly quickly. Costly mistake .

[scoobyh123]

My Coupe had 205/55/16s as standard on Prestige rims. That was a 95 car. I believe the KV6 Coupes had 16" wheels as standard so should have 205/55/16s at 32psi all round. The 17" wheels as fitted to the Vitesse ran at 34psi all round.

The only tyre size i've known to break the mould (on the 800 series at least) of the same pressure all round is the 15" tyres where they are 28 and 34 as you pointed out further up.

[n1tr0_9]

I used Martrim when i recovered the headlining in my rover 200. Very helpful. They send me loads of samples too which was good.

[Fastback]

First reasonble day, not raining, gale force winds, cold and any mix of the above.
Working on the Vitesse as I was thinking of getting the turbo reconditioned but the nuts seems totally metalurgically fused and with restricted access for only a small 13mm spanner, suddenly didn't fancy it. However did take the opportunity to solder together the headlight wires instead of the 'chocolate block' that somebody had previously used, since the battery was out having been charged. The car hasn't been used for 4/5 weeks.

So to the point; I started the car, which it did without hesitation and let it run for a few minutes. I wanted to check my light fix; sidelights, fine, dip beam, engine dies! Ok, the mainbeam was active so came on with the dip but why did it stall the engine? I restarted the car and went through the procedure again, no real issues apart from a slight drop in revs and the multimeter was showing a drop of about 0.4V (to 13.9V) when main beam switched on. Is that within expected tolerance? Bulbs are standard 55/60W.

Also, I noticed the rubber gasket between the throttle body and the inlet manifold is leaking on the throttle body side but unfortunately I can't find a part number and was hoping somebody might be able to help please. In fact if there is an EPC in pdf format out there, that would be fantastic.

[scoobyh123]

If you bring the revs up to ~1500rpm the alternator should hold 14.4V on a cold regulator and 14.0V on a warm one Mark, even with the headlights on. I suspect having been woken from hibernation it's feeling a bit lazy so might need a bit of a run to get up to full voltage again.

As for the turbo to manifold and downpipe nuts, make a solution of 50/50 acetone and Carlube ATF-U, shake it up and dribble, brush or spray it on them and the threads. Give the threads a bit of a wire brush too if you can and repeat the application of WMP (Weapon of Mass Penetration) then use a 6 side socket (pref impact rated and an impact wench) and they should shift - even with a 2' breaker bar they shifted on the last one that needed the same!

Make sure you keep the WMP sealed when not in use and shake it each time before ue as it has a tendency to separate when stood. I mutilated an old brake cleaner aerosol by drilling a 5mm hole in the bottom, cutting the brass valve insert from a tyre valve, cleaning it up then pushig it into the hole with some "extra" force. Bit of solder flux, blow lamp to heat it then ran solder into the hot joint and left to cool.

Obviously i'd removed the valve core beforehand and with the can upside down once cool, used 50ml syringes to add firstly ATF-U then acetaone (separate syringes) to get 400ml total (4 syringes each @50ml/syringe =200ml each), refitted the valve core, pressurised it to 100psi with the compressor, dust cap on, shook it then used it. Now i just shake and use, re-pressurise when necessary. Cheaper, easier and much better than WD40 or similar and helps derust things too.

[Fastback]

Thanks for the recipe and I'll revisit the turbo soon. However, perhaps a slightly more pressing matter needs attention. Behold, my slight leak ;



This is much worse than I thought yesterday (ok, I'm holding it open but that can't be good), probably explains the power loss amongst other things. I even can't indentify the part required. Any pointers please?