Timing Belt Failure and Turbo boost solenoid problems -Help!

[TommyS]

Firstly hi all, this is my first post on the forum!
I am now on my second Renault Megane 1.9DCi Sports Tourer (56 plate)
My previous 04 plate was a great car and no trouble. This car (56 plate) is proving more troublesome!

I has covered 120k miles and was told last year when I bought it (115k) that the timing belt was done at 100k.
On starting the engine two weeks ago day I found it lacked power and sounded very rough. The engine warning light came on with "check injection" warning on the dash.

Due to where I was and the time of night (after a late night of work) I had to soldier home a further 200 miles.
As this point I read the warning codes using my OBD and got the following:
P0340 - Camshaft sensor
P0670 - Heater module
P0235 - Turbo Charger Boost Sensor

I took it to a garage and they confirmed the warning codes and thought it was a timing issue.
Knowing it would be expensive I then took the car home and proceeded to investigate the timing myself.

Findings:
- Aux belt was shredding on one edge.
- The aux belt tensioner pulley bearing had failed (causing the belt wear/shredding)
- The Timing belt was in poor condition with cracks in it
- The timing belt had clearly slipped (7 teeth)

This explained the rough running and the noise (probably due to the pistons kissing the valves!!)
I thought this was simply the problem and hence fairly easy to fix...
On lining up the engine at TDC I found I couldn't get the camshaft in the correct position and the inlet valves were hitting the top of the piston.
Only one reason for this - the cam shaft pulley had slipped.
Reading various stories on how this cam pulley key shears I took it off and sure enough it had.
However post shearing it had jammed in a new position allowing the engine to continue running and not completely self destruct!! (very lucky! Has anyone experienced this before?!)

I am still not sure which event happened first - the jumping of the belt of the shear of the cam pulley key. I would guess the belt failed first?
Risking the fact that the valves may be damaged but not wanting to take the head off I continued with the repair job...
- New Cam pulley fitted.
- Engine re-timed with a new belt and tensioner.
- New Aux belt and tensioner

The engine started fine.
However - on going for a test drive I noted it lacked power.
I then read the error codes and noted that error code "P0235 - Turbo Charger Boost Sensor" still remained.

I then tested the Turbo Boost Pressure sensor and it worked fine.

On starting the engine from cold it's fine, however as soon as it gets warm and idles for ~5 seconds the engine warning light comes on and the signal to the Boost pressure solenoid stops causing the Turbo to stop delivering boost to the engine and hence the car is sluggish.
On restart the car is fine again and drives/turbo's fine until idle is maintained for a short duration (~5 seconds).

Anyone have any ideas on what the problem is here?
It only happens when the engine is warm and has only started happening since the timing failure.
Any help most appreciated!!

[Keyholder]

shot in the dark

Have you checked all realavant wires to sensors in the local area ?

[fredcamp2]

Is this a wind up if your vehicle is only 1 tooth adrift it will only turn over very slightly before locking up so I can't fathom how you drove this vehicle as you state with 7 teeth adrift. Maybe you can elaborate a little bit more Regards fredcamp2

[TommyS]

Have you checked all realavant wires to sensors in the local area ?

Keyholder - I am thinking now it may be the MAP sensor that is the problem.
All the wiring to the sensors appears to be fine.
I used my OBD2 and Torque App to read the settings - the current MAO sensor reads 77 KPa with the engine off and very similar with the engine running at Idle. (76-78 KPa)

When I rev the engine (before the engine warning light gets a chance to come on) I am getting suitable Boost pressures - up to ~25 PSI.

Can anyone tell me the sort of pressure reading the MAP sensor should be returning both with the engine off and running at Idle?

I thought atmospheric pressure should be ~100kPa.
Anyone got any OBD readings from their vehicles?

[TommyS]

Is this a wind up if your vehicle is only 1 tooth adrift it will only turn over very slightly before locking up so I can't fathom how you drove this vehicle as you state with 7 teeth adrift

Fredcamp2 - I was as surprised & amazed as you are - but I can assure you that this really did happen.
I have various photos showing the timing pre belt removal and also videos with sound of the engine running before the belt change - it did not sound good at all!!

My only explanation is that the offset of the cam pulley on the cam shaft compensated for the slipped 7 teeth of the Belt.
I carefully marked out the belt with tipex before removing it and measured it up against the new belt which had the timing marks on so I am confident on my figures.

When I ran it with the timing out it was very low on power, the slightest incline would reduce the car to a max speed of 30mph!

Also - does anyone know what the engine head design is like?
Are the Exhaust valves recessed into the Head and hence wont hit the pistons?
In which case if the cam shaft timing was delayed relative to the crank shaft it wouldn't actually cause the pistons and inlet valves to meet?
Thoughts?

[Keyholder]

I know on the 1.9dci ( 53 plate - f9q 800 (A) engine that they are slightly recessed into the head but not by very much. 2mm at very most.

But still even if they are recessed they should of still touched im sure- due to speed etc.

Personally if it were my motor, id rip it apart and check the internal damage, no doubt i could probably bet that somethings been bent.

The very least id get a compression check done on each cyclinder if there is a bent valve somewhere, then get a air fitment gauge on there and listen for air either out of the exhasut or inlet side to see which valves are bent..

If no air escapes then hey presto you know no valves are bent.

This should take a garage no longer than 40 mins.

[TommyS]

But still even if they are recessed they should of still touched im sure- due to speed etc.

Yep - I am sure they will have "touched" too...
The failure happened at start-up and I am guessing the following events happened:

- The cranking of the engine put the belt under sufficient strain to slip...
- The belt slipped
- Piston met valves - resulting in sudden rotation on the cam shaft and shearing of the cam key.
- Cam pulley locks into a new position on the cam shaft and engine continues to run, albeit very rough!!

I have some photos of the timing before the belt came off and you can see for yourself just how far out it was!
How do I upload photos on this blog?

Keyholder - I agree, I should probably take the head off to have a look at the valves.
However I don't have the time to do it myself at the moment and cannot afford to send it to the Garage.

How many hours work is it to take the head off?
Cam I get a compression test kit that uses the glow plug bore? I don't fancy taking the injectors out.

For now I am driving it with everything "crossed" and it seems to be running ok.
I have done 200 miles...

[Keyholder]

I know it took me roughly about 2 hours to get my head off, and it was the first time i touched a renault diesel.

Im not to sure if your engine is the same as mine being a newer model and i THINK they have changed lumps, but these diesels seem easy enough to work on theyre just in a tight space.


For inspection checking, your best bet is from the injector housing. injectors arent that hard to get out tbh.+ thats how most kits are made tbh.

[TommyS]

2 Hrs isn't too bad...
I shall have a read of the Haynes Manual and see what is involved.
Agree with you - for all of my experiences to date the engine is fine to work on, there is just no space to do the work!!

Request to anybody that has OBD/torque access - are you able to tell me what your MAP Sesnsor is reading?
Mine is currently reading 78MPa with the engine off (atmospheric) and 77MPa with the engine Idling.

I am thinking this may be the reason for an engine warning light coming on at tick-over but would like to confirm before splashing out on yet another sensor!!

[AlexB]

MAP figures are supposed to be within 100-250 kPa range, 100kPa at idle. Pressure below 100kPa means partial vacuum; can be an obstruction somewhere. This is for my F9Q-800 120ps diesel.

[TommyS]

Thanks for this Alex.
Yes - I thought it should be ~100 kPa for atmospheric.
Currently my OBD2/Torque is giving the following readings:
- Sensor Disconnected: 50kPA
- Sensor connected and removed from the inlet manifold (Atmospheric): 78kPa
- Sensor connected and in the inlet manifold with engine off (Atms): 78kPa
- Sensor connected and engine running: 77kPa
- Sensor connected and engine under load: ~200kPa

Alex - Do you have any OBD figures for the MAP on your Vehicle?

[AlexB]

Yes, the figures are as I wrote... Please have a look a the diagrams as well.

http://www.tboneandporcini.pwp.blueyonder.co.uk/testrun1.jpg

[TommyS]

Thanks Alex. It looks like my MAP sensor may be faulty then.

That's a great set of graphs. I have yet to do some proper logs and display the graphs but it is next on the list of things to do.
Currently I just view the real-time dashboard.

What I have often wondered is where is the most economical point to change Gear from 5th to 6th is (assuming std driving conditions and driving on the flat etc etc).
Have you ever done this calculation?

[AlexB]

This is for 1.9dci 120ps

5th to 6th at 70mph under slow acceleration, otherwise 4th to 6th at 70mph.
6th to 5th at 60mph, unless you are slowing further down and intending to skip a gear, in which case you do 6th to 4th at 50mph.

It is economical, because driving below 1800-2000rpm will cost you a DMF, which is £1100 (more at dealers).

[Wickydude]

care to elaborate on that rpm range and dmf, Alex? On local roads I go to 6 at 50mph when i'm at a constant speed. 1500rpm or so, seems to run just fine. 1.9 130bhp version.
I mostly shift up at or just below 2000rpm in any gear.