Vide cache recourse

I think I mentioned previously, I purchased a secondhand VW van from a car dealer at the end of September. As soon as I got home with the van the engine warning light came on. After a bit of back and forth with the dealer I checked the error code and it said ‘glow plug control module to PCM circuit’. The car dealer diagnosed this as a problem with a relay, which he sent me and I installed. All was well but then the warning light came on again with the same error code. I went back to the dealer again and they are particularly unresponsive. I’ve been very careful to communicate with email, despite them calling me, to make sure I have a log of the time and process etc. I haven’t done alot of km’s, in fact, relatively few in the almost 3 months that I’ve had it. The car dealer said that the error code was not a serious problem and that I could continue to drive the van as normal, but I must say, I’m a little reluctant, and just want to resolve the situation.

I want to try to drive this whole process to a conclusion, so wondered if anyone else had a similar experience and if anyone triggered the vide cache process, and if so, what that process looked like in terms of steps to take. I’d certainly welcome any input, as I’m getting a little tired of the current situation dragging and having to constantly follow up with the dealer.

Don’t want to sound negative but the fact you installed the part yourself might not play in your favour as the dealer could say its your fault for doing so. Maybe an independent assessment from another mechanic on paper would confirm the problem. Just be very wary of deciding to go the legal route, it costs and arm and a leg.

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Very much don’t want to go down the legal route. I just wanted to understand the process to be able to make sure the dealer is clear that I’m aware of this French buyer protection. It is a little frustrating as they take their time in responding, so want to ‘inject’ some urgency!

It probably just needs new glow plugs & the dealer is more or less right, once it’s started and running it wouldn’t be using the glow plugs anyway.

BTW it’s “vice caché” - vide caché would be a hidden void and vide cache - not actually sure.

The same thing came up on the Mazda, not sure f it was one of the faults that was thrown when the battery was under par, our (UK) mechanic ignored it and it went away.

I’m a bit surprised they didn’t say “bring it back we’ll check the wiring and glow plugs for you” though - that is a bit of a red flag regarding levels of customer service, a new glow plug (and the odds are it would only need one) is maybe 20€

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It depends if they seized in the head, they sometimes can be a real ba****d.


Rightly or wrongly I purchased the van from a dealer over near Lyon so quite some distance, otherwise I’d have just driven over to him and insisted he sorted out the situation. I guess one of the downsides with ‘distance buying’.

When I start the van for the first time in the day the engine takes a bit to start i.e. seems to turn over a few times before actually getting going, but then after that it starts quickly. Would that be a symptom of glow plug failure?

Any cold larger diesel engine will turn a few times at this time of year as it uses compression to get the fuel igniting, glow plugs help pre heat the cylinder making it easier to start, but above maybe -4C it should start ok but with a bit of churning.
I have seen cars with knackered glow plug relays so no glow plugs at all start at -8C abet with a lot of churning to get them going and it puts a strain on the timing belt if they have one and not a chain.
Turning the ignition on and off a few times waiting on the glow plug light going off in-between will help as it builds up more heat in the cylinder before cranking.

Thanks alot @Griffin36 that’s very helpful to know. I’ll give the on off on off on off a go to see if there’s an improvement with the ignition. Touch ward, it’s remained quite mild here until now, so guess the real test will be Jan with lower temperatures.

The bigger the capacity of the engine the harder it gets to start with a diesel, bigger cylinder capacity to heat first.
I wasn’t only because of of fuel waxing that lorry drivers used heaters under the engines during winter, a warmer engine was easier to start as well.


I vaguely remember, early 60s (I was very young) our road was being tarmacked and the contractors (or more likely the local council workers back then) lit fires under the engines of the road rollers, then putting a shovel full of embers on the top of the engines before starting them.

Diesels were extremely bad for waxing in those days, clogging the lines, filter and injectors.
Modern fuels with there additives are much much better, below -12C you run into icing problems in the fuel as well.

My dad and grandad used to add a drop of washing up liquid to a full tank of diesel when refuelling their London Taxi’s during the winter months to reduce the waxing issue.

Adding paraffin was one of the things they used to do, but actually all you were doing was introducing more paraffin wax, adding petrol worked better but reduced the lubrication on the pump and injectors hence adding 2 stroke oil to diesel during the winter to increase lubrication.
Cold flow improver (CFI) that dissolves the bonds in paraffin wax is used nowadays, by breaking up larger crystals into many smaller parts, a CFI enables paraffin wax to pass more smoothly through the filter especially as filters go down to a lower 45-micron for filtration due to the high pressure systems compared to the old injection systems that were used in older engines.
I’ll shut up now :yum::laughing:

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Did you resolve the problem? If so how so.