Cam-driven PAS=vurnerability, truth or myth?

[nametooshort]

Another one for you French car experts out there.

Someone was telling me how the whole cam-driven PAS pump idea was a really bad design, because it causes a potential very massive vulnerability.

They said something along the lines of, that if you park the car with the steering in a certain position (full lock I think), and then go and start the car on a cold morning with the steering still in that position, bad things happen. Something to do with the steering rack using max fluid in that position, and cold viscous fluid on a cold morning.

The proposed scenario was that it puts too much pressure on the cam belt, which makes it skip teeth or break, which kills your engine.

That sounds kind of dubious to me, because:
1) cam belts are very strong, and that thing is only a little 10mm V belt, which should slip/break at waaaay less pressure then a cam belt.
2)I don't think steering racks use more or less force depending on which position they are in?
3) I am sure the pump would have a pressure relief valve.
4) PugCit are NOT idiots, at all, what so ever, they knew what they were doing back then.

But, I thought id ask anyways. Remember, I don't know much about...well almost anything in general lol.

So, was that guy 2 months ago talking garbage? Or was he correct?

[spider]

I do remember hearing about it, but then again you could have a vac pump seizure too, more likely on the belt drive one given very rarely anyone will bother to check its oil level.

You are putting a bit of load on the belt yes, but less load than the cam I'd expect. Not really thought about it that much to be honest.

[Oldpug]

Peugeot/Citroen had cam driven pumps for years with out any problems,lots of models Petrol & Diesel.All the old Peugeot XU diesels had two belts being driven by the camshaft,one for the PAS & one for the vacuum pump.I had an old 405 Mi16 which had two belts being driven by one of the camshafts,PAS & Vacuum pumps.There are Citroen models that had the LMS suspension pump being driven by the camshaft.

[nametooshort]

Hmm, lucky I asked! I didn't even know the vac pump had oil! How do you check the level?

[Oldpug]

That`s got me too ?? I can never remember putting oil in Peugeot belt driven vacuum pumps?? changed lots of diaphragms on them.

[spider]

Its got a square plug on the side, similar to how you check the transmission oil level.

I took mine off to drain / refill it as its difficult to do in situ. I cannot remember what I put in it though, it would of been probably EP80 or some BV at a guess as was a few years ago now.

The cam driven ones are usually splash fed so nothing to do, its just the belt drive ones that need looking at.

[Homer]

I was told never to leave any PAS equipped car on full lock due to potential damage.

[spider]

I think that's due to the pressure relief / return valve when at full lock, I think its more important to not "hold" it at full lock for too long, at least in my opinion.

[CitroJim]

My experience and belief with this setup on both 205s and 405s is that the belt is likely to slip (it being a thin vee belt) long before the cam is at risk...

[dieselnutjob]

I remember XUD engined BXs had a bit of a run of broken cambelts. It took a while to figure out why they were breaking whilst other PugCits were not.

The reason was a loose hydraulic pump belts.

If the belt is loose then when the system demands pressure and the hydraulic pump cut in the load could actually stall the pump until the slack in the belt was taken up. This would then put an enormous shock load on the cam shaft and eventually break the belt.

The solution was to keep the belt tight so that the pump couldn't stall.

[nametooshort]

I guess that only applies to the hydraulic pump, right? That thing has a much higher load then just a power steering pump, since it lifts the whole car up. A Power steering pump would not be that demanding?