I tried Steel Seal in my V6 which will have a liner because it's an all aluminium engine but it still has the same symptoms. Not sure if I followed the instructions exactly though, the car hasn't been on the road since but I have fully warmed it up and left it running for quite some time.

I own a vehicle with a V6 engine that has a blown head gasket, it pressurises the cooling system when running and even if I let it cool down then leave it cool for a few days before opening the rad cap there's still pressure in the cooling system.

I strongly suspected it had a hg problem but confirmed it using a sniff test.

I have cooling system pressure test equipment which I intend (when I finally get around to it) to use to try to identify which hg is leaking by pressurising the system when it's cool and see if I can see any coolant weeping into cylinders using a borescope through spark plug holes. Not sure if this will work though, because it obviously leaks whilst running (when there's a lot of pressure in the cylinders) but seals against the smaller pressure in the cooling system with the engine off and/or cool... So maybe this won't work because even if I pressurise the cooling system to (say) 5 bar pressure that still won't be enough pressure to cause coolant to leak into cylinder(s), and such pressure could be enough to ruin the hg that currently isn't leaking.

Chrisp38 wrote:

Lpgc wrote:

Wonder if some cars won't turn the heated screen on if ambient temperature is high?

Is there no way to connect an Ammeter or just listen for alternator whine?

I did wonder about ambient temperature but I'm getting voltage on/off with the switch at 28 degrees.

Ahh yes of course

Yes I meant connect the ammeter to just the hw wiring not at the battery

Wonder if some cars won't turn the heated screen on if ambient temperature is high?

Is there no way to connect an Ammeter or just listen for alternator whine?

Maybe consider just buying a set of second hand injectors? I know cleaning products can work to fix lesser injector issues such as duff spray pattern but if they're bad enough to cause a misfire I wouldn't fancy the chances of a cleaning product fixing them.

I recently bought a set of 6 second hand injectors (for a V6 vehicle I was tasked with fixing for the firm I worked for) for around £60 including shipping.

The firm runs mostly large vans and flatbacks that were originally diesel powered but they remove the diesel engines, fit LS3 petrol engines and convert them to LPG. But the V6 vehicle I mentioned above was the company owner's brother's own car, it had been parked in the works yard for 18months and had a constant misfire on at least 2 cylinders. Before I worked there they'd dropped the engine and fitted a new valve, the ECU had been left unplugged and had got full of water so they sent that off to have it fixed. Still the misfires remained. They blamed the ECU and had another ECU cloned to match the one they thought hadn't been fixed properly. Then it refused to start at all. I diagnosed and fixed it... The reason it wouldn't start at all was because the immobiliser had kicked in after the ECU didn't recognise the key after 5 attempts at starting, so I coded the keys to the ECU. Then it started but only ran on 4. Then it wouldn't crank... Both due to 2 cylinders being hydraulic locked with petrol due to stuck open injectors (no doubt due to dirt ingress because the guy who removed and refitted the engine didn't flush the fuel line or injector rails before reconnecting). Then it still only ran on 4, due to 2 failed coil packs. I was thrown a curveball on that because one of the mechanics there said he'd already ruled coil packs out by swapping the positions around... I expect either a coincidence or the coil packs failed due to something related with the fuel locks but the mechanic reckoned 2 failed coil packs had caused ECU failures, I doubt there was a problem with the first or second ECU after they came back from the ECU firm first time but they mistook stuck open injectors, failed coil packs and need to recode keys for an ECU problem.

It could be a petrol injector problem or could be the failed lambda sensor / learned fuel trims / less likely learned position for the IAV that's the problem?

Or even something (Pitagora?) that's not connecting all the petrol injectors when it's running on petrol?

I've forgotten what brand(s) of petrol injector cleaning fluids I've used in the past, Wynn's rings a bell. Maybe ask Dai Brace (ClassicSwede), I had a chat with him last night (first chat in maybe a year), I know he highly rates certain brands of injector cleaning fluids but I forget which. I've just sent him a txt so he might see this thread.

Recently I've been working for another firm a few days a week, they have a very well equipped workshop including petrol injector testing / ultrasonic cleaning equipment (which I've used while I've been there). If you'd asked me last week or the week before you could have maybe sent me your injectors and I'd have put them on the machine for you but I got a message from the firm's boss this week to say they don't need me this week... and I doubt they'll be needing me again soon.

Edit - Dai txted me back and sent me this link https://www.forteuk.co.uk/product/petrol-specialist-injector-cleaner/

I reckon whether series or parallel plumbing is best depends on all the factors mentioned above (flow rate of reducer, flow rate of heater core, etc). But the height of the reducer is also important... The heater core is always going to be low but some reducers are mounted higher than the expansion tank (are the highest part of the cooling system). If the reducer is the highest part of the cooling system then if it's plumbed in parallel it won't see any flow at idle because all the heater water flow will go through the matrix, if it's plumbed in series it's forced to flow through both. But if we think of the heater circuit as a whole (the matrix plumbing and the reducer plumbing) we can be pretty sure that parallel will flow more through the whole than series could... It's just that as a whole we don't want 95% to go through one unit (matrix or reducer) leaving only 5% to go through the other.

I reckon a 10mm feed is a bit small for an LPG reducer on a V8, fine at low engine loads but may not flow enough for sufficient reducer heating at higher engine loads when the reducer is losing a lot of heat due to evaporating a lot of liquid gas to vapour inside. You could try it but it would be worth monitoring reducer and gas vapour temperatures at high engine loads. Most LPG reducers (with the exception of a few well knowns such as Bigas which have 10mm water feeds).

PC38 wrote:

My LPG diagnostics shows both lambda sensors (one brand new) sitting resolutely at 5 volts (GEMS engine).

I don't know who fitted your LPG system but is the LPG ECU even wired to the lambdas? If they're not connected you might get a reading of 5V from LPG software anyway.

A few years ago I converted a few MX5's and Euno's to LPG for private owners, I've driven them (probably early marks) but never lived with one. A more refined take on the Triumph Spitfire which is exactly what they were designed to be, great fun but cramped and uncomfortable for a long distance and more power would make them more exciting.

There was an MX5 specialist dealer that always had a few second hand ones on display in their shop window in Conisbrough not far from me, just Googled them, seems they've moved even closer to me, now on South Kirkby industrial estate.

I've got the ML55AMG up for sale on Ebay at the moment, item number 325656518072.

Sorry I didn't drop you a line Leolito. If you're seriously interested in buying it let me know and we'll see what we can do, but I do want it shifted fairly soon.

Morat wrote:

You're a madman ;)

I know hehe! But to be fair I think it's a different alternator on the AMG, a bigger 150amp one and seems a wider belt. Dunno if the ML320 alternator would have fitted, probably a better bet to get the 55AMG alternator reconditioned. I've been flat out at work for a long time, recently less busy and it seemed I'd have just a brief opportunity to tidy the yard up and shift some old cars, old boat etc... Otherwise if I messed about I might lose the opportunity and the yard remain full of old cars. Thinking about buying a bigger (and functional lol) boat or motorhome, need the space.

Only had a quick look at the 3 files you shared but the last one does look a lot better, and I think if the readings stay the same that should be the last of your mixture error codes ./ MIL light problems.

There probably isn't much point in looking at plugs - The equivalence ratio reading is the actual mixture, so if you're looking at plugs in attempt to check mixture there's little point as we can already see that mixture has been correct. It does go lean (fully lean as in no fuelling at all) when you lift off the throttle at cruising speed because it's supposed to, but that won't affect plugs because there's no burning going on under those conditions. It does go rich when you put your foot down under boost conditions, again it's supposed to and even a carb would go rich at full throttle.

I'm pleased to read it seems changing the MAF has delivered positive results.

Hope it stays the same! If it does stay good for the next few months it would be interesting to see if the old symptoms returned if you refitted the old MAF.

Had a chance to look at the 'gifted' ML today, the alternator is getting very hot as soon as a battery is connected even without the engine running, so looks like the rectifier is shot. Dam, I just scrapped another ML and could've swapped alternators :-(

I'm wanting to tidy the yard up a bit and make a bit more space because I'm looking at buying a boat and/or motorhome and there's been too much crap in the yard for years anyway.

So first off I scrapped an old Merc ML 3.2 7 seater I've owned for around 5 years. I bought this ML in a rush when I needed a tow car to pull my caravan to Cornwall, bought it one day and used it for the tow the next day. New iridium plugs in it (12), new tyres on the back but a bit tatty, AC didn't work (compressor), PAS reservoir to pump seal issue so it leaked PAS fluid out over a couple of days, osr bumper needed a bracket fabricating. One previous owner car, I could have fixed it up but it wouldn't be worth much so I scrapped it and got paid £250 scrap value. No problems there, it was a runner and the local bloke who picked it up made short work of getting it on the back of his truck, just drove it on.

Different story getting rid of the Jeep. Flat battery but it wouldn't crank on turn of the key from a good jump start. I got it started by removing the starter relay and jumping the switched connection.. Jump starting from my car it started straight up after maybe 3 years since it was last started but it would only run for 3 seconds before cutting out... some sort of immobiliser issue. Brakes were binding and I only had a normal car to pull it with if I were to use a rope, so I rigged a longer wire from the relay connections to the cabin so I could touch the wires together and start it from inside then move a few feet during the 3 seconds the engine would run whilst trying to avoid crashing into my car that I was jump starting it from. Took around an hour to do a total of around 80 yards including a 5 point turn for the Jeep and the jump start vehicle having to be constantly repositioned around the Jeep in a kind of vehicle dance but I managed to manoeuvre it in the yard to get it nicely lined up with the entrance for when the scrapman came with his truck to collect it. Phoned the scrapman I used for the ML... "I'm in Tenerife mate, back Tuesday". So I told him "I want it gone before then really but if it's still here on Tuesday I'll call you again". Phoned the driver of another scrap firm I've used in the past, not so close but still only 10 miles away. He said "Phone our office mate, I'm just a driver". I phoned the office they said "We'll be sending a different driver and she's a lot better looking". My mate was with me, he was hurt badly in a car crash in his 20's and doesn't work but we've known each other all our lives and he comes to see me at work and 'help me' a few times a week. He says "Heh I might come tomorrow then if there's a bird coming"'. The scrapyard office hear him so they're all laughing. Next day the driver turns up to collect the Jeep, looks a bit young and giddy but manages to reverse the truck down the drive OK. I don't want to make it seem I'm looking over her shoulder so I don't watch her attach the tow line from the truck to the Jeep. Goes to winch the Jeep onto the truck, the Jeep doesn't move but it's front wheels turn inwards because she'd attached the line to the steering arm instead of to the axle and the truck moves backwards. At this point I release the line and attach it to the axle. What should have been an easy job winching the Jeep onto the truck turns into half an hour of faff because of the front wheel tow-in so not being able to steer it very well and because the tow-in pushes the ramps inwards during the climb. At last it's on the truck, spend half hour talking about her horses with her taking pics of my old boat because her mate might want to buy it, then she says goodbye without giving me the cheque for £340. All good in the end though.

Had a Merc ML55AMG in the yard for around 7 years, not mine, it belonged to a customer whom had me convert his newer Merc ML63AMG to LPG around 7 years ago. When coming to collect the freshly LPG converted 63AMG he asked me if he could come in his 55AMG, drive home in the 63, have me LPG service the 55 and come back to collect the 55 next week. It turns out that in that week his then missus discovered he was having an affair with his secretary, he ran off with the secretary, the 55 was the missus daily driver.. The car was left with me for 7 years and the owner was very difficult to get hold of. But I managed to get in touch with him last week and he agreed to give me the car to compensate for the storage, a logbook in my name for it arrived today. I'm not sure what to do with the 55AMG now, it has a 'special' LPG system because it's previous owner was an LPG installer and went to town fitting multiple LPG tanks to maximise range, I quite enjoyed driving it when it was roadworthy. quick for a small 4x4 SUV type thing and could be a 'street sleeper' if de-badged to shock boy racers from the lights, or pull a boat when I buy one (or existing caravan). But it's obviously deteriorated in 7 years, brake pedal goes to the floor but I haven't had a good look around it and ML's do have a common problem of rusted rear brake lines so the brakes might be an easy fix. Got it started but it was running on 6 cylinders at first, it turned out rats had eaten some engine bay wiring! But I've fixed that and the V8 now runs nicely. Maybe if it seems structurally good I'll fix it, maybe then keep it myself or sell it, if it seems it'll cost too much to put back on the road I'll sell it as is. Maybe regret scrapping the other ML because the door sills were better on that one than this and same colour.

Wonder if boat exhaust manifold/risers and mating plate to an Alpha/Bravo boat leg are available for the Merc 5.5? If so it might be an idea to buy a boat with a knacked engine and stick the 350/400hp Merc 5.5 in a boat designed for a 4.3/5.0/5.7 Mercruiser/Volvo setup.

If you'll be changing the Maf anyway you might as well do that and see if it makes any changes to fuel trims.

For the benefit of others who might be interested in reading this and for my own notes...

Had a Whatsapp chat with Khemitude today, showed me around the engine bay during the video call. It's got a (relatively recent) AEB badged AEB2568 with old Bigas reducers and Valtek type30 injectors. The 2 injector rails are each fed from a separate reducer, no balance pipe. The gas inlet points on the are in the 'old skool' position on the Thor plenum so quite a distance from petrol injectors and engine inlet valves. This also means that each rail feeds 2 cylinders on one cylinder bank and 2 cylinders on the opposite cylinder bank, and without a balance pipe this means it's likely 2 cylinders on each bank get higher pressure gas and hence richer mixture than the other 2 cylinders on the same bank.

Plan is for the OP to come to me maybe next week. I'll replace the 2 old reducers with a new MJ one and calibrate it as well as can be.

Just had an old mk2 (facelift) Jeep Grand Cherokee 4L straight six here with a very similar problem... The Bigas reducer was leaking gas not to the cooling system but to the gas output, so when the system was turned off gas pressure rose to >3bar and was ballooning gas pipes. I replaced the Bigas single reducer with a MJ reducer. One of the Valtek type34 injectors wasn't working at all (coil OK but no output of gas) on number 1 cylinder, so I left it set to run on 5 cylinders on gas with number 1 on petrol until the owner has replaced that injector himself. It also has an occasional lambda signal shorted to heater circuit problem, so the owner is going to replace the pre-cat lambda sensor.

Turns out it's one I converted in 2008 but I originally fitted a closed loop mixer system (back then I'd offer customers the choice of a mixer system or sequential system and the mixer system would be a bit cheaper), so the front end components have been changed since I originally converted it.15 years ago. Heh, first thing I said when looking under the bonnet was "Wow your ECU is just hanging and resting against the engine". He says "Well you fitted it". I said "I didn't fit this mate lol". My original receipt (which he brought with him) showed I'd fitted the mixer system but it now had the sequential system fitted.

Rough idle could be due to any or a combination of worn injectors, points of gas entry in plenum too far from engine valves, calibration.

But your immediate problem is the reducer(s) leaking LPG into engine coolant.

Most reducers have 12mm gas outlets, Bigas reducers normally have 10mm gas outlets.
Most injectors have 12mm gas inlets but Bigas injectors normally have 10mm inlets and 10mm inlets are available for V30 injectors.
10mm to 12mm inline pipe connectors are available.
If your install has 10mm reducer outlet(s) and 10mm injector inlets you may need to either change injector inlets to 12mm or use a 12mm to 10mm inline connector when fitting a reducer that has 12mm outlet. Since 12mm pipe is better available than 10mm pipe (and you may need to reroute piping to use just 1 reducer) and since most injectors are only available with 12mm inlets it would be better to change piping to 12mm if you're changing the reducer.

I think I understand the pipe routing you've described. The installer may have intended the pipe between injector rails (with the T to the AEB025) to act as a pressure balance pipe. But if that pipe is narrow diameter it may not be able to flow enough enough to balance pressure between rails in some conditions (e.g. big difference in pressure output of reducer, certain engine loads).

Gilbertd wrote:

Simon, LPGC on here (and on www.lpgforum.co.uk) is just off the A1 near Doncaster. He will no doubt see this and reply shortly. Sounds as if you have correctly identified the problem and it may be due to a bodged attempt at rebuilding the reducers (or they are simply knackered). There will no doubt be a single reducer that Simon will recommend. Are we talking GEMS (pre-99) or Thor (99 onwards) motor?

I'm here ;-)

I agree it's going to be one or both of the reducers leaking gas into coolant, most likely just one,

My go-to reducers are MagicJet (Compact version and Extra version), those produced over the last few years all have a very wide range of pressure adjustability, either version (Compact or Extra) would be a good choice of reducer for a P38 in terms of both physical and technical and they're reliable.

If 2 reducers are fitted the gas outlets need to be T'd together. There's only one pressure sensor so if one reducer feeds one bank and the other reducer feeds the other bank the pressure sensor will only read pressure from one bank and the other bank could be getting very different pressure. It wouldn't cause any leaks or coolant pressurisation but would cause different fuelling to individual banks.

Does the system have a Bigas ECU (probably AEB2568?) and Bigas injectors?

I'm in South Elmsall, between Wakefield and Doncaster.

Hehe yes cheating in a way but I have to cut all injector negative pulsing wires anyway. Even if I'd looked up wiring colours on a diagram there'd still be the need to confirm which colours went to which injectors, with my method there's no need to confirm.

Might as well have the data logger connected. In fact you could use it to make sure Stft's don't hang at extremes for too long, if they're hanging at an extreme change the throttle position and the Stft's will momentarily return to zero which resets the timer for Stft hanging at extremes and prevents throwing a MIL code before Ltft's are learned.

Before because if it works it could fix it, then you wouldn't need to buy any parts.

I'd do it with a cold engine, that way you're doing the same as I did when I first found out it could reset the underlying trim. When I'm cutting petrol injector wires to wire in an LPG system, sometimes the easiest way of finding which colour wire leads to which petrol injector is just to cut a wire and see which cylinder the petrol ECU reports has the misfire and open circuit petrol injector.