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I once had a service engineer who worked for me who changed everything until he had sorted the problem. It was good for turnover, but proved too expensive for some customers. Both they and I cheered when he found another job! That was on electronic process control equipment in the 70s.
Originally Posted by camallison
The problem with hi-tech is that there are so many possibilities with sendors and valves and human nature leads garages to tend to replace all these first.
That really is good news Andrew - what led them to change out the turbo? Previous experience? As you say, it didn't show up in diagnostics.
Ureka! I have finally got this one sorted. I have been at Renault Trucks at La Cala on the Costa del Sol for 7 days over the last two weeks. Finally, after trying everything the diagnostics threw up, they changed the turbo.
It was a mechanical problem. The casting for the cover had cracked at the three narrow support legs which allowed it to impeded the adjustable fan blades at times. Being mounted in a vertical plane, it would still work at times which explained the intermittent nature of the fault and difficulty tracing.
The cost of all the work done by four garages working and replacing sensors and valves according to the diagnostics exceeds the cost of replacing the turbo!
I question the value of diagnostics and software driven engines over good mechanical know how. It has taken a year to sort this but I am so glad I have. It's great to have full power back.
Thanks to all of you that have helped.
I am going to have to visit a Renault Truck Dealer on this one.
What I have found is that Renault Trucks SAS have an app for the IPhone that shows all the nearest dealers to your location. I can plan my route via one.
Other Renault owners may find this app useful to have when travelling anywhere.
Thanks Stanner. I will certainly try that tomorrow when it's light and I am sober. Dangly bits protected.
These intermittent faults are the hardest to determine and defining the problem is 90% of the way to the solution.
I know it's something simple but my experience is with older cars and not with diesels.
Any other suggestions also welcome. I'll try Anything
one more thing it could be (and something I found AFTER paying for a new EGR) is a split pipe between the turbo and the manifold.
They are quite thick and stiff ( ) and the split often only opens under heavy boost conditions (just as you describe) and the loss of boost triggers limp home mode.
It is very difficult to diagnose and it even beat my usually very on the Ball (sorry ) Fiat techie. I only twigged it by accident and did a temp repair with Duct tape - 1000% improvement.
Try squeezing all the piping between the turbo and the inlet manifold and see if any collapse easier than the rest.
Then do the same to that one with the engine running (keep any dangly bits you want to retain away from any moving bits) and if you feel/hear a rush of air or change of engine note that could be where your problem lies.
I would appreciate any advice on this as I am in Morocco and the problem has got worse. I can cope with till I get back to Europe but might call in on a Renault dealer in Spain or France.
What I need is help identifying the cause of the problem because the experts I dealt with in the UK haven't found it.
So far I have been to three separate garages on five ocassions including Renault Trucks in Reading and the bill has totalled over £1,000 and the problem still exists. Four separate items indicated by the diagnostics have been replaced. EGR. Vacum. Something I can't remember and the acellerator pedal.
It is getting worse. Today driving from Gorges du Ziz to Azrou the light came on over 30 to 40 times when climbing requiring the ignition to be turned off and on again.
The symptoms are not consistent which is why it's do difficult to pin down. Two of the garages spent ages driving and trying to pin them down.
I feel that I have lost low end torque below 2000rpm. I am having to rev higher in a lower gear. At higher speed in fifth or sixth I am having to change down when meeting any slight incline and run at nearer 3000 rpm when I would expect it to handle it easily.
On steeper climbs that I would expect to do in third I am having to use first and second at 2500 to 3000 rpm wheras before I didn't.
Any advice would be appreciate. Thanks
An update on this.
Replaced the EGR valve two weeks ago (major job, difficult accesses). Still have the problem
Replaced the pressure sensor this week (different garage). Still get the same problem. Booked in again for Monday.
Symptoms are at speed on motorway up steepish incline under load. Light comes on at 2800 - 3000 rpm in fifth gear when acellerator downed. Goes into limp home mode. Cleared by switching ignition off an on again.
Originally Posted by Stanner
The EGR valve is only to take the NOX gases out of the exhaust - something that isn't checked at the MOT. It was added to comply with EEC construction requirements, but not testing requirements.
I am stripping the front end of our Master this weekend, and will see how easy it is to get at the EGR valve which is buried a long way down, according to the workshop manual I have.
PS- second-hand valves are around £120, so the price quoted by the OP is possibly supply only - fitting could be a couple of hours job.
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