I saw this thread earlier today and watched it in case the OP, who has only ever made this one post, turns out to be a spam robot.

It won't hurt to post this now somebody else has already replied lol.

I was aware about nitrogen finding leaks but I thought the main reason it was used to test AC systems instead of air was because air might contain water vapour?

nigelbb wrote:

A few years back I got some new tyres at ATS & they offered for a price to inflate my tyres with nitrogen promising some magical benefit. I declined on the basis that air is about 80% nitrogen already so that would be good enough for me.

Nitrogen is more pressure stable with varying temperature than air, so on race cars when they want to keep tyres at a specific pressure they might fill them with nitrogen. But for a road car if your tyres are getting hot it's probably better that they do get the bit of extra pressure provided by expansion of the air in them?

I know someone who has just used Seafoam in his Nissan VQ35 engine.

He had suffered a blocked cat (common problem on those vehicles) and after clearing the cat debris the engine smoked and the inlet tract in the manifold to one or more of the cylinders on the engine bank that'd had the blocked cat were found to have evidence of oil in them, not to mention low compression on one of those cylinders.

Some suggested that the problem could be stuck rings and that Seafoam might help so he used Seafoam the other day but at the moment the engine still smokes. Some Youtube videos suggest that the engine smokes a lot during using Seafoam and will smoke for quite a lot of miles after using it. Fingers crossed but I don't think it's fixed his problem and probably couldn't have been expected to fix it.

By most accounts though it does do a decent job of carbon removal? Some vids claim even more and show engines that had problems such as sticking hydraulic lifters that were sorted by using it.

If you want to increase range on LPG of a P38 there's always the option of fitting a second (and a 3rd, possibly even a 4th tank).

Adding a single extra tank could easily more than double capacity/range, and you could fit it yourself for around £250... but it would take up around half the boot space.

Triple range for around £500 but not have much boot space left at all.

Maybe quadruple range for £1100 but have no boot space left and lose the petrol tank.. So then it would be monofuel LPG.

Side point - adding extra tank(s) can also increase the filling speed.

I'm not surprised that people don't like the idea of monofuel LPG, I too feel re-assured to know that I can fall back on petrol if necessary.

But I'm also not surprised people don't much like the idea of effectively only being able to recharge an EV at home and at work, not have the ability to fall back on petrol and not have the option of doubling range for £250 or even for £25k.

It would be handy to have the ability to refuel with LPG at home but that is something I could have if I really wanted it or if it was necessary. Even before LPG I could have stockpiled petrol at home if I'd ever felt the need but I never did (although I have stockpiled red diesel in the past!). It is more important to me that I can take my car anywhere with confidence of being able to find somewhere to refuel it close to my ideal route, refuel quickly, has long range, I can tow with it, I didn't have to pay £50k for it, and I don't have the uncertainty of it needing a new fuel tank in a few years that might cost £20k to replace.

I'm not a climate change denier and I acknowledge vehicle engine emissions have played a big part in climate change but the work I've done so far has helped reduce CO2 emissions to the extent of taking hundreds of vehicles off the road while not replacing them with brand new vehicles that were made at the cost of a lot of CO2 emissions. Until electric vehicles have better range and the charging infrastructure is much improved petrol/LPG dual fuel vehicles are still not a bad bet - I am busier now than I have ever been despite BP and Shell pulling out of the market and despite turning down contracts to convert hundreds of taxis.

A lot of EV buying has been company cars for office workers... who have since proven to be able to work from home, therefore it won't matter much if they have a dirty great diesel on the drive or an EV because they won't use it much in future, so why still allow subsidies for them to buy a new EV? If the buyer claims it's for leisure use and they want to use it to visit their remote farm in Scotland from London every weekend then that's their civil liberty and a different matter but an EV less than a Tesla would be a poor choice for that type of use.

Clive603 wrote:

Current needed to trigger the build failure warning system depends on how the system works. As I understand it the way P38 electronic control gubbins is fairly close to the CanBus standards. Although, like everything else, the actual magic smoke control is done rather differently from the modern way.

As I understand it CanBus and related, pre Can Bus, systems have three ways of doing the bulb monitoring.

1) Low level pulses to determine if a bulb is actually fitted during the power-up self test on a modern car before everything comes on line and the car can be started. Fortunately doesn't appear to be done on the P38. Things that do tend to need proper CanBus bypass doobies. Although its still a good idea to wait until the self test lights have gone out before starting up.

2) Low current detection circuits to determine if there is an operational bulb. Generally these need to see the something around the impedance of a cold bulb before the drive transistor can turn on. Easily done. From memory the headlamp drive transistors in the BECM have the necessary monitor ability implemented in the device itself hence 4 terminals rather than the usual 3. Osram suggest that a current of around 1/4 the normal, i.e. hot, draw of an operating bulb will suffice. I suspect this is what the P38 uses. Simple, effective and good enough for its purpose.

Pretty sure thats how I worked out the the parallel resistors for the LEDs I put in my reversing lights about 6 years back. Now up to two young active glow worms per light level rather from the standard one geriatric and seriously undernourished glow worm. Better than nowt I guess.

3) Operating current monitoring. The electronics continuously measures the actual current draw of the bulb or illuminator and flags up anything outside that specified for that particular vehicle. We certainly haven't got that although the transistor drive light controls are quite capable of implementing it. In Europe driven by TuV (German) homologation requirements, with a bit of deliberately malicious input from the French, which essentially demand that a modern car has a Car Configuration File of all specification and approved part fitment details hidden in its electronic brain. Anything not on the internal approved list is verboten for that vehicle. So switching stuff from a different specification version becomes a nightmare.

And you thought BECM issues were bad!

Its all getting rather worrying. My second bike is a Yamaha GTS (the funny front end one) and the fraternity are getting reports of German inspection failures when using a 120-70 front tyre instead of the standard 110-70 despite it being an approved alternative fitment because it doesn't actually appear on the original homologation data supplied by Yamaha. It is said the machines are over 10 years old getting the changes approved requires the whole homologation process to be re-run by Yamaha. Which isn't going to happen. Apparently, in Germany at least, the powers exist to invalidate insurance, ban the use of and possibly confiscate anything that doesn't exactly comply with the on file paperwork.

Regrettably pragmatism is out of favour these days.

Clive

(1) and (2) are easy enough to get around with a bit of work, a cheap way is just to wire 12Watt brake light bulbs in parallel with whatever bulbs you're fitting. I once fitted some Xenon's on my dad's 2004 Vectra (this was in 2006), they continuously flashed and the dash lit up with bulb warnings, but they worked perfectly with break bulbs wired in parallel and the dash warning lights went out. Instead of using resistors you can just use bulbs, a resistor flowing same current as a bulb is going to have to dissipate as much heat anyway? Handy under-bonnet lights for checking the engine at night too lol.

If the problem isn't as simple as battery voltage are there any multimeter tests he can do to see if the TC clutch, output speed sensor, etc, are electrically working (even though this wouldn't necessarily prove they were mechanically working)?

I don't know the P38 boxes as well as many here but such problems on other gearboxes can be due to bad electrical connections such as the connector between the box and vehicle loom or internal on the valve body. Sometimes breaks on electrical tracks on the valve body can be a DIY repair.

Is there a common component that could go bad that could cause all these reported problems? For example on other boxes you can expect to get codes for certain speed sensors if a clutch is slipping or not engaging due to a bad solenoid, in which case you get the code for the solenoid but you also get a code for the speed sensor. If there is a possible inter-relation between codes it points toward an actual gearbox fault, if there is no possible inter-relation it could point more towards a generic electrical problem such as a bad earth or as Bri said battery voltage.

Most people's concerns about ethanol are about fuel system components compatibility.

Then there's the well known differences with calorific value and octane rating and the lesser well known different stochiometric ratio.

On some vehicles with compatible fuel system components the IAV may need to open to a different extent and fuel trims may see limp mode triggered.

A lot of E85 compatible modern vehicles have an 'ethanol content' stream in OBD live data, the detected value of this shifts between fuelling, ignition timing and IAV default position maps.

Nothing wrong with experimentation, I'd probably want to try it myself if I wasn't converted to LPG and E85 was available.

It may be handy to have a fully featured Nanocom but I believe a lot of cheap generic code readers will show MAF readings on P38s? Or even possible to just connect a multimeter to it and compare voltage readings? For comparative purposes just the voltage should suffice... The OP doesn't necessarily want to see if he can calculate bhp from airflow readings, just see if his seems to be flowing as much intake air as others.

Welcome

I've known engine power be effected by different grade oil effecting hydraulic lifters.

I believe generic code readers will show a figure for MAF readings on P38's, though I think whether the readings are meaningful/accurate or not depends on the year and engine ECU of the P38. I think I've seen some daft figures on some models using some code readers like 300g/s which would equate to enough air for around 375bhp. But some scan tools show maf voltage and the interpreted g/s reading.

A good test will probably have to involve actually driving it flat out rather than just revving it while parked up,, and don't even bother looking at the screen until you get to quite high rpm with foot to the floor. A good uphill stretch helps minimise road speed during such test.. It would probably be helpful if the scan tool plots a slow moving graph of MAF reading.

If the camshaft is worn then the engine won't make as much power when you put your foot down... with a worn cam the lower power is due to the engine not breathing so well, i.e. not getting through as much air.

The MAF measures airflow, so maybe compare your peak MAF readings to those of other owners on forum and the results should give a lot of insight into whether your valve train and cam see as much airflow as others, i.e. whether or not your cam seems worn ;-)

Gilbertd wrote:

Presume you told him the simple test for that is to run on petrol and see if it still pressurises?

I did.

Sorry the late reply, back from holiday now.

Hugh phoned me last night, I'm on holiday in Wales at the moment but we had a chat.

I think he's suspecting the problem may be the LPG pressure reducer allowing gas to enter the cooling system, so may just need to replace the MJ pressure reducer.

Perhaps the valve in the port you connected to leaks - If so it wouldn't leak with the pressure tester connected.

No wish to add fuel to any fire (there's a pun in there somewhere heh!) but the subject is interesting...

Didn't BMW use propane as refrigerant in AC systems at one time? More efficient than the usual refrigerant gasses and isn't carcinogenic in the event of a leak (or leak in the presence of a flame)? While of course the risks of propane entering the cabin and setting on fire in e.g. a crash situation wouldn't make up for it not being carcinogenic, on balance plenty of us carry a lot more propane around inside vehicles and some older cars like Jags had the petrol tank inside the vehicle body behind the back seats.

Do these Halfords AC kits contain R134, propane, or something compatible with R134 (and if so what and how does it compare to R134)?

Not had any beer yet but will be having some in about half an hour ;-)

Is it R134 in Halfords AC charge bottles or something else that is compatible with R134 but not regulated (regulated as in should only be supplied to AC pros?

And if it's something else is it as good (efficient etc) as R134?

IIrc Sloth or someone else once said it wasn't R134 in Halfords bottles? At the time I thought there was R134 in them (thought I'd read it on the side of the bottles) but now it's been said it's technically illegal to supply R134 to none pros I wonder again if it is R134 or something else.

Like Sloth I too have never known an AC machine pressure test, only vacuum test, and have known pinprick holes seal under vacuum only for refrigerant to leak out when the system is pressurised. But then again I won't have seen as many AC machines as an AC pro.

What I have done is pressurised an AC system myself just using compressed air to check for leaks (see if the system holds pressure), I know it shouldn't be done and moisture in the air could mess up the dryer (and/or other parts?) but rather than waste an hour at Kwik Fit for an AC system to pass a vac test then leak refrigerant when I drive away (so I have to return for money back - they give a 2 week guarantee even if the system leaks) I've done this when I've suspected a pinprick hole that might seal under vacuum.

I have a few Halfords AC recharge kits, at least one intact, at least one I've cut up so I can connect an air compressor to the LP port. I wouldn't gas up an AC system from flat using a DIY kit (partly because it's cheaper to let Kwik Fit do it and the Kwik Fit guarantee) but when I have a car that takes 0.995 kg of refrigerant and I see the Kwik Fit machine only wants to put in 0.85kg of gas when my reg is entered I have to wonder if the AC system would benefit from having a bit more gas than the Kwik Fit machine puts it (even though I tell the operator to manual over-ride and set the machine to 0.995kg) because I wonder if the vehicle manufacturer knows it should really have more than 1kg of gas in it but there might be some sort of environmental threshold at 1kg - Indeed Kwik Fit charge a lot more (iIrc double their usual fee) to charge an AC system that takes more than 1kg of refrigerant. The Halfords kits come with a pressure gauge that you set according to ambient temperature, the instructions say charge with gas until the LP port is at a certain pressure when the clutch is in... but machines don't do this kind of operational test (or operators don't do the operational test) ? On a few makes/models after having an AC machine fill I've found that the AC system gets colder with the engine at idle if I put just a but more gas in it from a DIY kit... Got to wonder if the machines short-change on the weight of gas they measure they're putting in?

Years ago before AC became as popular in the UK and systems were mostly R12 if you spoke to an AC guy they'd be reluctant to regas a system without changing the dryer. Most of them didn't have machines and couldn't do a vacuum purge/test, you just parked on the street outside their house and they'd come out with a camping gaz size green bottle and connect it to the LP port... with enough pressure the AC clutch would kick in and pull the gas into the system while they watched the sight glass and filled it til there were no bubbles.

Unlikely to be brakes if it's a braked trailer but worth a mention if they haven't been mentioned already.

The thing about wheel bearings on trailers is you don't hear them when they've gone wrong like you do on a car.

Which reminds me, I need to change wheel bearings on a trailer (not a car trailer) before I can use it and I need to use it at the end of next week.

Out of my area of expertise but there's a guy on another forum I go on who's an audio/visual specialist (his day job) and a whiz at doing stuff like getting/ incompatible signal feeds to appear on factory or aftermarket displays. If there seems to be a problem getting a reversing cam picture to appear on an existing screen I could invite him to come on this forum if anyone likes? For problems like that he's usually able to advise/sell an inexpensive gizmo that gets it working and is happy to chat.

Is the reducer mounted high in the engine bay? More chance of it drying out when the engine is off if it is and that can lead to crystallisation and other problems. To keep it full of water when the engine is off it shouldn't be higher than water in the expansion tank.