406oc.co.uk

Since we appear to have lost all the good posts of the past, can someone run through the steps of diagnosing and (hopefully) fixing a non-working turbo?

Ok I've been thinking and reading up about this... There's 4 things I can think of that could be likely wrong:

1) Vacuum hoses. These aren't mentioned anywhere on the "how a turbocharger works" pages I've read in the past. According to the parts diagrams, there's only one hose going to the turbo, and that goes to some sort of electrically-controlled valve (Number 1 here - wtf does it do?) which has a hose going to just before the throttle and another to somewhere I haven't worked out yet. I'm guessing this hose is how the ECU controls the boost (how?), and a leak here would stop it from working? Hows the best way to test this? Disconnect the turbo-to-valve hose at the valve and feel for suction when the engine's revved? Or would disconnecting it stop it working in any case?

2) The aforementioned valve not working

3) Seized turbo. I remember some talk about this in here from before the forum hacking. I think the advice given was to stick yer finger in and see if it turns, but I can't recall the specifics. I'm guessing the easiest way would be to remove the air outlet pipe, but how do you get to the jubilee clip to do this? Above all, is it actually accessible?

4) Dump valve stuck open. Guess a quick feel would tell if this were the case?


It the worst comes to the worst and the turbo's seized, how can it be replaced? Does the engine need to be dropped down, or something equally impossible for the home DIYer?

I've just seen this. Does this mean the 406 turbo is WATER cooled???

Define 'not working'... Not spooling at all? Laggy? Smoking?

'not working' in this context means the turbo doesn't appear to be doing anything.

Performance and engine tone is the same as a working XU10J2TE at low revs, but when I'd expect the turbo to be pushing (about 1800-4000rpm), there's nothing. There's no dump valve 'psssst' when coming off the accelerator at high revs (4500rpm) and the only time I've ever heard the turbo whistling on one of these cars is when i had an accident and had to drive to a breakers yard without a bonnet, so it's impractical to listen out for it spooling.

Sounds like something as simple as a boost leak - try checking all the main boost hoses and then the vacuum hoses. One good (but messy way) is to go crazy with some flour or talc in the engine bay, blip the throttle and see if you get a white face from somewhere....



Did it just stop boosting one day?

Tiny Tim wrote:Did it just stop boosting one day?

Unknown. I bought the car the other day. As soon as I got in it for a test drive I realised it had no turbo boost, but the (at the time) owner was genuinely surprised, so it's evidently been like this for a couple of years.

Good thinking on the talc. I think I'll give that a try when I next see the car (now my dad's). In the meantime I'll get some and try it on mine (also a 2.0 turbo) so I know where air *should* be moving about

I really hope it's an obvious air leak. I had a look at mine earlier and it looks nigh-on impossible to get anywhere near the turbo even just to poke a stick at the impeller!

Oooo errr

dont expect much left of the stick afterwards

mjb wrote:Ok I've been thinking and reading up about this... There's 4 things I can think of that could be likely wrong:

1) Vacuum hoses. These aren't mentioned anywhere on the "how a turbocharger works" pages I've read in the past. According to the parts diagrams, there's only one hose going to the turbo, and that goes to some sort of electrically-controlled valve (Number 1 here - wtf does it do?) which has a hose going to just before the throttle and another to somewhere I haven't worked out yet. I'm guessing this hose is how the ECU controls the boost (how?), and a leak here would stop it from working? Hows the best way to test this? Disconnect the turbo-to-valve hose at the valve and feel for suction when the engine's revved? Or would disconnecting it stop it working in any case?

The Vacuum hose is just for wastegate actuation, and pull on blow off valve piston / diaphram... if the hose to the blow off valve is split the blow off valve will constantly be open so boost will not build, instead it will recirc into the intake when using the stock bosch item.

mjb wrote:2) The aforementioned valve not working

The electronic solenoid your talking about is part of peugeot's electronic boost control system, if this is faulty typically the engine light will come on and ecu will be in limp mode until its replaced. It can sometimes just end up locking open, which means the actuator is open all the time and the turbo does not produce boost.

mjb wrote:3) Seized turbo. I remember some talk about this in here from before the forum hacking. I think the advice given was to stick yer finger in and see if it turns, but I can't recall the specifics. I'm guessing the easiest way would be to remove the air outlet pipe, but how do you get to the jubilee clip to do this? Above all, is it actually accessible?

Yes it is, but the easiest way to identify it is the intercooler feed pipe from the alloy charge pipe on top... if this pipe collapses when you rev the engine, the turbo is siezed as the engine is sucking the air in and the air is not being forced through the pipe... you can also check the comp wheel too... it is accessible but you will have to get on the floor under the drivers wheel... and mess about a bit.

mjb wrote:4) Dump valve stuck open. Guess a quick feel would tell if this were the case?

mjb wrote:It the worst comes to the worst and the turbo's seized, how can it be replaced? Does the engine need to be dropped down, or something equally impossible for the home DIYer?

It's an easy job.... I've done it so many times and guided so many DIYers through it.... first time, it will probably take you about 6 hours... to swap a turbo, but if you have to service the unit first then, add a day to it... I'm almost done with a guide on how to service your turbo for the KB...

mjb wrote:I've just seen this. Does this mean the 406 turbo is WATER cooled???

Yes sir, it sure is.... I think you'd want to be watercooled if you were stuck behind the engine between the block and the bulkhead lol

niz406 wrote:The Vacuum hose is just for wastegate actuation,
...
The electronic solenoid your talking about is part of peugeot's electronic boost control system, if this is faulty typically the engine light will come on and ecu will be in limp mode until its replaced. It can sometimes just end up locking open, which means the actuator is open all the time and the turbo does not produce boost.

So the hoses attached to the solenoid are the boost control which works by opening the wastegate, which causes exhaust gas to bypass the turbo.

I know from experience (leaky radiator triggering JUST the low coolant light) that limp-home mode is just the ECU stopping boost, so that could still be the case here. Do you know what host is sucking and what's blowing so I can see if it's working?

Yes it is, but the easiest way to identify it is the intercooler feed pipe from the alloy charge pipe on top... if this pipe collapses when you rev the engine, the turbo is siezed as the engine is sucking the air in and the air is not being forced through the pipe...

You mean number 4 on here? http://www.peugeotpartscatalogue.co.uk/D8F/0/03L61A.HTM

I had that down as being a pretty solid pipe! Take it there's no reason I can't just push the linkage on the throttle body to get this to happen... Will it compress if the turbo's not seized but say the wastegate's stuck open so it's not being spooled up?

you can also check the comp wheel too... it is accessible but you will have to get on the floor under the drivers wheel... and mess about a bit.

Comp wheel? Dammit stop using lingo I don't understand!

Do you mean get under, pull the big fat pipe on http://www.peugeotpartscatalogue.co.uk/D8F/0/03L40A.HTM off and turn it by hand?

mjb wrote:If the worst comes to the worst and the turbo's seized, how can it be replaced? Does the engine need to be dropped down, or something equally impossible for the home DIYer?

It's an easy job.... I've done it so many times and guided so many DIYers through it.... first time, it will probably take you about 6 hours... to swap a turbo, but if you have to service the unit first then, add a day to it... I'm almost done with a guide on how to service your turbo for the KB...

Hurry up then When you say "easy", do you mean "easy with somewhere off the road, an engine crane and loads of special tools"? Is servicing a turbo really a viable option, or is a visit to a breakers yard more likely?

mjb wrote:Does this mean the 406 turbo is WATER cooled???

Yes sir, it sure is.... I think you'd want to be watercooled if you were stuck behind the engine between the block and the bulkhead lol

I thought turbos were oil cooled because the heat generated would instantly vaporise water?

mjb wrote:So the hoses attached to the solenoid are the boost control which works by opening the wastegate, which causes exhaust gas to bypass the turbo.

I know from experience (leaky radiator triggering JUST the low coolant light) that limp-home mode is just the ECU stopping boost, so that could still be the case here. Do you know what host is sucking and what's blowing so I can see if it's working?

1) hose going from intake pipe to solenoid is +tive pressure (boost)... 2) pipe from intake manifold is for -itive pressure (vacuum) 3) pipe goes to the actuator on the turbo... Pipe 1 + 2 are used to balance predefined pressures in the expected boost / fuel map.

If there is a fault spark will cut and limp mode will be in effect !

mjb wrote:You mean number 4 on here? http://www.peugeotpartscatalogue.co.uk/D8F/0/03L61A.HTM

I had that down as being a pretty solid pipe! Take it there's no reason I can't just push the linkage on the throttle body to get this to happen... Will it compress if the turbo's not seized but say the wastegate's stuck open so it's not being spooled up?

Yes, that pipe will collapse if the turbo is siezed.... if the DV or WG is stuck open the pipe will still expand under rev's until a certain point.... even with the DV / WG open the engine will still pull better than no boost pressure....

you can also check the comp wheel too... it is accessible but you will have to get on the floor under the drivers wheel... and mess about a bit.

mjb wrote:Comp wheel? Dammit stop using lingo I don't understand!

Do you mean get under, pull the big fat pipe on http://www.peugeotpartscatalogue.co.uk/D8F/0/03L40A.HTM off and turn it by hand?

Yes.... the big 90 degree dend off the intake port on the blower.... try and turn the compressor wheel to confirm if its siezed or not !

mjb wrote:Hurry up then When you say "easy", do you mean "easy with somewhere off the road, an engine crane and loads of special tools"? Is servicing a turbo really a viable option, or is a visit to a breakers yard more likely?

I mean, two jacks... at a push! ! ! 2 axle stands and something to lie on lol

It's a Subframe off job.... unless you have a crane then its... easier... apparently !

mjb wrote:I thought turbos were oil cooled because the heat generated would instantly vaporise water?

No the water is used to cool the oil jacket / bearing journals to stop coking and help maintain oil viscosity...

Any more info needed?

niz406 wrote:Any more info needed?

Probably, but I won't know until later... I'm going to see it as soon as by blood alcohol level drops below the limit. Zzzzzz

I wrote all that after a night out on the pop.... was surprised to read it this morning and see, such good use of grammar and correct spellings...

Dammit the breathalyser's telling me i'm still well over the limit.

Glad I've got it though. Hangover's wearing off and I feel fine to drive. Ain't worth risking my license tho

OK the hose to the intercooler isn't collapsing. In fact it feels very much like mine (working turbo) does. It was too wet and snowing today to get under the car and poke the turbo by hand...

I've checked the instrument cluster lights and they all work now so there's no indication of it being in limp-home mode. Definitely no boost though. Did a reset of the ECU just in case, and re-seated the solenoid plug just in case. Didn't expect that to have much effect though and due to the heating blower not working (since fixed) we couldn't take it for a spin to confirm...

Any ideas I can try next time?

meh time to dig up an old post, as it saves typing a new one and covers all the same things that has just happened to me.

mjb did you ever get this problem sorted out and if so what the hell was the problem / solution, as my motor is showing the same symptoms as yours did in this post.