My 406 Break - bought it for work, but already love the car

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joydivision
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Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

I was spot on - the problem was created by the additional check valve I installed. Today I bought clear fuel line tubing (just to discover that it was too small in diameter, but then found the right one at another store) and a bit of black normal flexible tube, as it revealed completely impossible to install the black original rigid tube on the connections, it's far too small, I don't know how they fit it in the first place... also I wouldn't want that, as I wanted clear tube to be able to see the air, if any. So, after much hard fiddling and some improvisation (I wanted to take out that little straight piece of black flexible hose and the white junctions, so the line would go direct, but I couldn't get suitably sized union pieces anywhere... as I need the car, I was forced to recreate the original improvisation with the new tubing - the old black tube piece was in a bad condition, who knows if it wouldn't let some air in?). Before final connection I used my "bleeding" trick, the syringe with diesel to fill the tube and pumped the primer bulb, then joined them and installed clamps. Tested and yeah! The little remaining air from this installation was purged within like 30 seconds and some accelerations, from then on a almost constant solid fuel stream could be seen, just on some harder accelerations a few bubbles would appear but also disappear as quickly afterwards. I made a short drive and the car behaved absolutely flawless, perfect power and acceleration until higher RPM, problem solved!! :)

So, lesson learned: two check valves in series are a REALLY bad idea. Unfortunately this also means I'm back to stage 0 about the fuel running back into tank issue.

Still I bought a new fuel filter element and ordered the O-ring that is fit in the bottom of the housing against the fuel heating part from the coolant lines, as I've read it sometimes develops minor air leaks. This because although the check valve caused the problem, the air must have come from somewhere (which would also explain why the fuel runs back into tank when parked uphill). I think your idea of coming in at the fuel filter housing might be right, as with the check valve aggravating the situation, it was after fuel filter that the majority of bubbles appeared.

But I won't have time to do this so soon, I have a lot of work right now, also the installed fuel filter can make a few more thousand kms.

If that doesn't settle the fuel to tank returning issue, I have one last idea (but I'm not sure if it's valid): in the fuel return line to tank, there's a fuel pressure regulator installed (or overflow valve, I think it's called here), what if that one is stuck open? Could that, together with minor air entry somewhere in return path, allow fuel to run back through injection pump and return line into tank?

Thanks again for all the patience reading my posts and useful hints :)

On another note, as I now have the front wheel triangle issue solved and two new tyres on, the car is ready to go to MOT (it's this month), here in PT it's a little less demanding than in UK, but still I'm a bit nervous as this is the first time with this car for me. When it's done I will report back, hopefully it will pass just fine.
joydivision
1.8 16v
Posts: 70
Joined: Fri Jul 02, 2021 7:18 pm

Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Here's the photo that I forgot to attach.
IMG_20211103_130204578_.jpg
(693.45 KiB) Not downloaded yet
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Doggy
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

Good progress, well done!

I think it likely the fuel running back to the tank is due to a less than perfect seal at the filter or one if the pipe connections in that area but I guess it can wait.

The overflow/pressure regulator valve is probably closing OK (or at least well enough) if you can run the engine at maximum fuel demand continuously, (accellerating hard up a hill for example).

Good luck with the MOT
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
2008 BMW E91 330i touring (we shall see......)
joydivision
1.8 16v
Posts: 70
Joined: Fri Jul 02, 2021 7:18 pm

Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Thanks.

Yes, that's what I'm thinking, too, but in fact this can wait, I don't even have any ramps here at home where I would park.

Ok, I didn't know the overflow valve was important for this, but yes, the car drives perfectly now, so this rules the overflow valve out, which is good (one less thing to verify).
joydivision
1.8 16v
Posts: 70
Joined: Fri Jul 02, 2021 7:18 pm

Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Went to MOT yesterday. It didn't pass yet, two issues, one of them serious. But there's also good news: mechanically, emission-wise and electrically (except for one fog light, that's the minor issue) it is all fine! :) Now for the serious issue which made it not pass: it's that damn oil leak I've mentioned before. My mechanic got the additional smaller leaks settled (just some connections that needed tightening) and I got the overall oil smearing of the whole engine coming from top of it settled by changing the manifold rubber joints. But that one oil leak right under the engine is still there and for them it's too much, has to be solved. So I called the mechanic and on Monday first thing in the morning I'll leave the car there for him to solve this problem with enough time and also clean thoroughly afterwards. Hopefully it's just some pipe connection (he said that oil circulates with quite some pressure down there). Just hope it won't take him too long, then the most costly will be the labour...

As for the minor issue, the fog light, I just fixed it today, was an oxidised connection, not a blown bulb. :lol:

So, next week I'll post updates.
joydivision
1.8 16v
Posts: 70
Joined: Fri Jul 02, 2021 7:18 pm

Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Just came back from MOT, it's done, it passed! :cheesy:

My mechanic found the origin of the oil leak and fixed it yesterday, then gave it a thorough clean. The oil came from upwards, behind the engine block, it was the seal of the valve cover, was in really bad shape. So it fortunately was an easy and inexpensive fix. I will still keep an eye on the ground under the car over the next weeks, as one never knows, it might very well still have some other minor leak, but I hope not.

So, I'm really happy with this and can now focus on the very few things that are still left to fix or that I want to improve on the car, listed in order of priority (though none of them is really urgent, which is great progress):

-1. change the air inlet piping, as it has that critically dangerous location behind the the fog light into the the wheel arc, way too low for the kind of floods we sometimes experience here. I already ordered a suitable pipe and have a clear idea of where the new inlet location will be.

-2. solve slight cold start difficulties and the "fuel running back into tank when parked on hill" issue (still needing some further investigation)

-3. fix RPM gauge not working (this one I tried to fix already, as you know, it's a tough one, but I will get it done one day!)

-4. change thermostat, as it MIGHT be stuck open or (more likely) not closing totally, as engine runs a little cold. Now with cold weather it can be noticed more clearly. Still have to do the pipe feeling test, haven't had time for this.

-5. Buy one of these "chinese" remote central locking units and install it, so that I can have working remote central locking, I always wanted this (my previous car, although from 2004, didn't have one) and this 406 supposedly had a remote, but the remote unit is broken (tried to fix it with no luck) and I don't even know if the receiver works, so this seems the most economical and easy fix.

-6. Next spring or summer, if I have time (or a little money spared), I will fix the two or three places on the paint work where there's deeper dents that have some rust. I might even do the job myself, I've done some (amateur, but acceptable) paint work before.

And that's it, looks like slowly I'm getting there 8)
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Doggy
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Re: My 406 Break - bought it for work, but already love the car

Post by Doggy »

Well done getting it through the MOT.
Sounds like you have most of the important/urgent issues under control.
Many of us miss our beloved 406's - enjoy yours!
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
2008 BMW E91 330i touring (we shall see......)
joydivision
1.8 16v
Posts: 70
Joined: Fri Jul 02, 2021 7:18 pm

Re: My 406 Break - bought it for work, but already love the car

Post by joydivision »

Oh yes, I'm enjoying it, since the start, but now that I've got everything important done, even more :)

I've also been enjoying this forum, although not having much movement, it's a place full of useful information as well as helpful and nice people.
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