1973 AC Model 70 Invacar, Visitors & Occasional Distractions

Taking a closer look at that wiring mess reveals the tail is attached to the aftermarket alarm sounder...so that's definitely thoroughly dead then. Good thing I erred on the side of "I don't think so" when asked by the insurance company if it had an alarm. I'll pull that out then and see if I can find the other end of this to at least confirm that there's no power going to it.

Yay, I get to stand on my head under a dashboard again!

On the running theme of seeing if I can get vehicle systems back up and running I made a run over to Formula 1 in Newport Pagnell so this could happen.



While the AC system was totally flat when I got the van I had noted on my first inspection that both service caps were loose, plus the condenser looks way newer than 20 years and 100K miles...have to wonder if a new one was fitted at some point and they just never bothered gassing it up? I still have a bottle with some dregs of dry nitrogen from goodness only knows how many years ago, which in its last gasp shoved around 40psi into this system a few days ago. Checking this morning showed the pressure hadn't visibly dropped. Having something in there had also allowed me to check that the compressor clutch worked and the compressor ran - albeit only for a couple of seconds as I had no idea if there was any oil left in the system.

It was a tense 30 minutes while the system ran the vacuum decay test (which basically is a leak check to see whether any air leaks back into it) was carried out - zero decay reported. Which says the system should hopefully be gas tight. It also shows it's reasonably dry (as water boiling off from the drier core etc would result in a *small* bit of vacuum decay).

Machine was happy with all of the tests and charged properly. Real test was going to be starting up, pushing the button and seeing what happened.



I should really have had a camera pointing at the service gauges to video it, but suffice to say they behaved exactly as expected.

It's a bit hard to tell you'd think when it's all of 6C outside, but the system was definitely working. Suction line definitely got cold and there was heat quickly apparent on the liquid line. Definitely colder than ambient air coming out the vents too... exactly what we were after. No nasty noises from the compressor (that I can hear over the rattle of an SDi idling next to it anyway...though I'd by lying if I didn't admit it's a lot more refined than an XUD).

Having working AC should really help me deal with the bit of damp in the cabin. Basically we'll run the heater at "as warm as I can deal with" on recirc with the AC on for a while and see if that helps. As the air con dehumidifies the air passing through it, that will help actively pull water out of the cabin.

Next significant jobs in mind:

[] Exterior clean.

[] Dismantle and clean EGR system as it sure it's thoroughly sooted up. Especially given I've no idea how long that vacuum leak had been playing havoc with things. Can't see any obvious signs of it having been apart before, so it and the intake pipework will be well due a clean if that's the case.

[] Paint front bumper so it looks slightly less scruffy.

Longer term I have an idea in mind regarding the paintwork as a whole...open to inspiration that others might have too though. I'm already finding myself really quite attached to this little van so I'm going to try to make a reasonably tidy job of things. The rust around the window over the cab will be getting sorted and we'll see what we can do for the offside rear quarter too before the aforementioned larger scale paint job too.

What colour do *you* think she should be painted?

Some good results all round with this - central locking, aircon, etc. Nice work.

White, with the Vatican City flag on the doors to be a pretend Popemobile?

Harlequin and noticeably different wheels.

So people know it is “Special”


I always think that if you are making the effort to repaint a car, it has to be stock standard or radically different like this.


My dad used to have no issue with getting a 3 year old car colour changed, maybe where I get it from.

My first car, a 79 Datsun 140Y, came back in late 1981 from the operational area on a pass and it was not white anymore.

Three years later it was painted again, blue this time for my brother.





Change is good.



Your paint may only be limited by your budget.

I say go big.

I actually think the wheels on there look okay, though they really need to be properly painted and with black or dark grey centre caps.

It definitely won't be getting bigger wheels or lowered suspension...the ride is firm enough as it is and I appreciate my spine remaining intact! Softer shock absorbers are something I may well look at down the road.

Today was time to have a look at the EGR valve to get an idea of how gunked up the system really was.

By the standards of most modern cars it's thankfully pretty easy to get to. The arrow is pointing at the vacuum actuator rather than the valve itself, but you get the idea.



Given the position of the securing collar I don't reckon it's ever been off. However the innards weren't anywhere near as bad as I was expecting.



Yes it's pretty grim, but I'm not unused to seeing these things totally choked solid on far newer vehicles.

Probably about 0.5mm worth of caked on gunk the whole way round.

The other side of the valve is more disgusting as it's sticky, tarry curse word as the PCV system feeds into the EGR circuit right next to the valve. I did dig an appreciable amount of gunge out of the valve body, but it definitely wasn't totally choked nor did it seem to be sticky.



I'd also been able to confirm that the valve is sealing completely and consistently when closed.

Reassembled everything...and absolutely no difference. Very slightly surging engine speed still there (it does exactly the same at any engine speed I found, regularly once a second), along with excessive smoke on light throttle.

Definitely have vacuum at the EGR valve, and you can hear it physically snap shut if you pull the vacuum line off. It however doesn't really have any noticeable effect on the running of the engine either way.

One thing I did notice is that when this behaviour is present, the rev counter also behaves slightly erratically, randomly twitching upwards from the actual engine speed - and it seems to do it more when on the throttle than off.

Then out of nowhere, the engine completely smooths out. The note deepens (because the flap on the intake, which I assume works in partnership with the EGR valve is now fully open), and the diesel clatter becomes a little sharper, so something has obviously changed - I'm guessing with the injection timing. Checking the EGR at that point shows there's no vacuum present, so the ECU isn't calling for the EGR system to be in operation. It's also noteworthy that after this point when things decide to behave that the rev counter twitching also stops I'm increasingly convinced these two symptoms are connected in some way.

So I don't think the EGR valve is the cause of this issue...bit it's definitely *involved* in it. Think the next step really will be to find someone locally with VCDS and get a look at some real-time data. Everything being fly-by-wire here makes guessing pretty pointless... imagine on a newer car we'd have a check engine light illuminated - but this car doesn't have one!

The rev counter misbehaving being clearly tied into it is making me think camshaft/crankshaft position sensors? Or however else the ECU gets the engine speed/position data...makes sense though if there's a disparity between the requested and reported engine speed, it would throw the fuelling all to hell.

Think it's likely been like this for a while so I'm not worried about it really, but I'll be damned if I'm not going to try to get to the bottom of it. Especially as the van drives so much nicer when this fault is staying out of the way.

We got any SDi experts on here?

Oh...and I've ordered a replacement engine cover. Looks quick and easy to fit/remove unlike many, so I'm not adverse to its being there.

Something which may well be getting changed in the not too distant future - which is a shame as they're only a year old - is the tyres. I had to brake moderately hard to avoid a suicidal pigeon this afternoon and discovered that these tyres really aren't great on a cold, damp road. Also the front ones have way more grip than the rears...great, aside from when all four wheels lock up, then the front regains grip well before the rear - which by then has started to try to overtake the front. It was a moderately firm braking manoeuvre, but I didn't expect quite *that* degree of upset. Even the big van would have been okay.

Methinks some Uniroyal rubber may be in the future. I will get the tracking checked in the meantime though - not least because the steering wheel is slightly off straight and means I can't see about 2/3rds of the warning lights on the dash when driving straight ahead. Bit of a daft design there from VW. Likewise the switchgear most of which is hidden behind the steering wheel.

Have you checked the throttle body? The tachometer fluctuation and engine surging point to this ... clean flap / butterfly and housing contact point with brake cleaner and an old toothbrush ...

..and check the state of the gasket

Here's a picture for reference...

This surging behaviour seriously has me intrigued. Managed to catch it doing it again today and got a better video properly catching it.



This clearly shows how it's essentially a regular "blip" approximately once a second that happens irrespective of the engine speed - and that during this behaviour she chucks out a shedload of smoke.

You can always *smell* that something is off when it's doing this, the smell from the exhaust lingers for ages. If you're in a car following it, it makes your eyes water apparently.

Physically disabling the EGR valve by removing and plugging the vacuum line to the actuator has no effect. I know the valve is moving as you can clearly hear it snap open or closed - and it sealed well enough that carb cleaner wasn't even seeping through the orifice while I was cleaning it yesterday. So I think the valve itself is innocent.

However if I unplug the *electrical* connection to the solenoid valve which controls said valve, the problem completely goes away. Idle immediately smooths out perfectly (it sounds to me like the injection timing or duration also changes as the engine note itself does change too), you hear the throttle valve in the intake snap fully open, and the throttle response becomes perfectly smooth through the whole rev range - and we see absolutely zero smoke aside from the expected tiny initial puff of black if you absolutely boot it, and that's not enough to be visible in the headlights of a following car. Also notable that any noticeable smell completely vanishes too...it just smells like an early 00s diesel VW.

Now I'm sure unplugging that would trigger an engine management light if I had one and I'm sure will have logged a fault code, and disabling an emission control device like this is illegal, so it's not a permanent fix...however it provides me with useful data to add to my diagnostic process and *definitely* puts the van in a less polluting state while I get to the bottom of the root cause. You've seen the cloud if you've watched the video above!

I need to make my reading today working out exactly what the sequence of operation is for the various bits of the emission control system on this engine and how the various parts interact with each other. I get the impression that understanding how that lot works will shed some light on what might be happening.

Decided that the Caddy could have a day off as errand running workhorse today so the main title of this thread can make an appearance!





Which went absolutely fine until I heard a suspicious "ding" at one point and saw something small and round disappearing into oblivion behind me.

When I eventually found somewhere safe to pull over, the cause didn't take long to find.



Ah. That's sub optimal. The air filter element was still present, wedged between the chassis and suspension arm thankfully (as they're surprisingly expensive), however the cover plate and wing nut are long gone. Even if I could spot it, as with so much of MK there's nowhere safe to pull over to retrieve it safely as it's on a 70mph dual carriageway with no pedestrian provision even vaguely nearby. So I'll need to find a replacement. Thankfully it's a bit of standard Steyr-Puch engine rather than a bespoke bit of Invacar so shouldn't be difficult to track one down, even if it may mean getting a whole new air cleaner assembly.

Guess we need to add "check air filter element retaining wing nut is tight" to the weekly checklist!

Been a little while since I had the time to do a proper update so let's have a catch up.

The Caddy passed a nice milestone while we were on the way to an appointment a few days ago. Thankfully I had my other half with me so was able to get evidence of it...as I was on the M1 at the time I couldn't exactly pull over to grab a photo.





Hopefully many more to come.

A surprisingly large parcel arrived - even more surprisingly quickly given it came all the way from Germany - for the Caddy. Got here quicker than some things ordered from an hour up the road.



Hardly mission critical, but definitely tidies things up a bit. Does make quite a noticeable difference to the noise level outside the van too so isn't entirely cosmetic. I usually hate engine covers, but this only takes about 90 seconds to install/remove and makes a good tray for putting things in so isn't a huge problem.

Does look like it's taken about ten years off the engine bay though!





While I was rooting around in the area I dropped the new cabin air filter in. Dead easy to get to compared to many modern cars which require you to stand on your head in the footwell and/or dismantle half the dash.



I'm quite used to seeing these having never been changed so was half expecting a solid black rectangle of unidentifiable organic matter to come out, but it wasn't actually too bad. Definitely due a change but it's definitely been changed sometime in the last few years.



You may recall me noticing some horribly hacked wiring in the engine bay related to the obviously long defunct aftermarket alarm system a little while back.



Which had also left a gaping hole in the bulkhead.



I've now found that end of the tail (buried behind the heater box), and each of the wires has been taped, heat shrink covered then the tail as a whole treated the same way. The actual alarm module is buried up behind the centre console and I didn't have the patience to go chasing that further today.

This lot was pulled out.



The above area now looks like this. By pure chance I found a bung sitting on the drive that was exactly the right size to fill the hole left by that alarm wiring.



Much tidier.

A friend dropped by today with their fancy diagnostic gizmo to see if we had any fault codes stored which might give us a pointer on what's going on with the twitchy idle/EGR issues.

As we had hoped there were a couple of codes stored.



The first of which is the interesting one.

"Motor for intake flap (V157) - sporadic - open/short circuit to earth."

The second code is expected as it's indicating the solenoid for the EGR valve being open circuit - because I've unplugged it.

This is really useful as it gives me a component to home in on with my investigation. First port of call is to make sure the wiring to it isn't obviously damaged as it is quite exposed. Then we'll give it a good clean, which it really wants anyway.

Tomorrow's task is going to be putting together the contents of this very heavy box, which arrived too late yesterday to do anything with...but should solve my pressure washer situation.





Should be a decent upgrade from a fairly low end electric pressure washer...and having 30 metres of hose to play with will be a massive help in itself compared to the four I'm used to. Putting that all together will be tomorrow afternoon's task.

A silly little accessory arrived yesterday for the Invacar.



Suitable replacement for the keychain that I somehow managed to lose back at the start of the pandemic.

Have also come up with a temporary solution to the air filter issue. This doesn't look in any way ridiculous...



To be honest it's basically only there to keep crud out of there until I can track down/manufacture a replacement for the missing bit of the cleaner housing. I won't be driving it like this given the insurance company may declare it's a performance modification...must be good for at least a 30% power increase of course!

I think that brings us up to date for now.

Very little to report as I've been running around all over the shop again this week so far.

Horrible sounding clatter/rattle when the engine stopped on the Caddy resolved.

Before:



After:



There was a good 3/4" of free play in the bonnet when latched and the nearside was rattling. I think looking at it the nearside hinge wants moving back fractionally too, that's a job for another day though. At least it doesn't rattle now.

Broken driver's door lock pull has now been replaced as it was bugging me.

The pull for the door lock on the driver's door was broken off at the top and it was bugging me. For the sake of less than £2 from a breaker it made sense to change it - they just unscrew.



Little details, but together they help make the big picture and make the car nicer to drive.

I think tyres may be on the menu soonish. For all these aren't at all old they just seem to have virtually no grip when the surface is anything other than bone dry. 2nd gear wheel spin shouldn't be a daily issue on roundabouts with 64bhp on tap when trying to move off anything resembling briskly.

Not really expecting to get any time to do much else this week as the diary is pretty full.