Now that my old untrustworthy truck has developed a nasty "sloppy bearing syndrome" (that is what I call it when no matter how much you tighten the bearing even to the point of locking the wheel the wheel still rattles) on the front axle I think it is time to retire the old sick mule to a farm. Work colleague of mine has a use for it as a mode of transport in his farm.
After looking around for a while I picked up a 2007 Renault master SWB. I initially wanted a Trafic but ones I could find were neither in reasonable condition or at reasonable price. The choice was rather poor in that I either had to pick a bashed up biscuit tin at reasonable price or nice clean example at exorbitant price.
It was a little oversized and a bit heavy on fuet on motorways but I think it is OK as I don't plan to drive it every day.
The van came with a glow plug warning light lit up indicating that at least one glow plug needs replacing. I have confirmed it using my Autel EU702 diagnostic scanner. Since the van is from 2007 it can detect most of issues using standard ISO protocol.
When it cmoes to problems with glow plugs sticking not just limited to Renault but a lot of common rail and direct injection diesel engines suffer from carbon build up around the glow plug shaft and when it is time to replace, the carbon build up grips tightly around the plug shaft of it and would not budge.
The plug casing is made of fastener grade steel and there is a core running through a 6mm bore. The core is about 4mm in diameter and connects to the heater element at the tip. When things go right you can unscrew it out just like normal fastener but when things go wrong, the hex head shears off just above where the thread is leaving most of the plug inside the head with you in despair.
There are number of tricks you can use to prevent such tragedy.
1) Get a reversible torque wrench and set it to around 5 kg-m the head snaps at around 6.5kg-m and do not under any circumstanes try to turn it passed the click. My torque wrench is not calibrated so you better try breaking an old one on a vice to check at what torque it breaks at on your torque wrench. Give it 20% safety margin when you actually set your torque wrench for the job.
2) Apply penetrating oil (diesel or ATF apparetly seems to work if you can not get a good stuff) liberally around the glow plug to be removed. Longer you let it soak deeper the oil will penetrate. (I am talking in terms of days not hours) I recomment at least 1 week.
3) Plan the job well and do not interrupt. The job needs to be done on a hot engine - you must part loosen all the plugs that are faulty. If the engine is cold there is no amount of penetrating oil in the world will loosen it. Have every thing you need ready and make sure it is done under some shelter.
4) Use a correct socket and don't try to take it out using an ill fitting tool
5) If there is something even partly in the way, remove it.
6) Don't rush
7) If it starts turning, loosen it in reciprocating motion to let penetrating oil reach deeper gaps. (I mean loosen a bit and tighten a bit until it can be turned easily)
8) If it breaks, do not panic - there is a way...
Here is one procedure that involves freezing technique
Stuff you need: Good vice grips, set of metric socket set, Plug socket 10mm - 12mm
PCB diagnostic Freezer spray, M4 nuts, penetratig oil, welding gloves or thick rubber gloves.
1) Soak the plug(s) for 1 week minimum
2) Ensure that you have checked the continuity of each plug and know for certain which one is faulty
3) Turn the engine on and drive around until the temperature gauge shows that the engine is at normal operating temperature.
4) Before turn the engine off, check that you have all the tools ready.
5) Turn the engine off and wet the plug where it meets witht the head with penetrating oil.
6) If there is a push-on terminal, screw the metal pin off to expose the terminal thread (M4x0.7mm usually)
7) Place 2 nuts and keep tighten it until the terminal pulls out of the casing.
8) Get a drink strow and put on gloves
9) Bring straw end to the now hollow head of the glow plug
10) Pump in the refrgerant for the freezer spray for about 5 seconds.
11) Ensure that the hand holding the straw is well protected form frost.
12) Pump it in again for another 5 seconds
13) Repeat it until the head of the plug stays frosty for about a couple of seconds
14) Hit it again with the freezer refregerant
15) Take the plug socket and turn it gently counter clockwize.
16) If it turns slightly, apply some more penetrating oil and turn plug clockwise by a couple of degrees.
17) Repeat 15 and 17 until the plug comes out.
Here is one that involves drilling
Here is what to do if the freezing method did not work or hex head of the plug broke off...
1) Get a drill set from 6.5mm to 10mm (or 8mm) in 0.5mm increments.
2) Compare the piece that broke off against the spare one you bought
3) Estimate how deep you have to drill just to clear the thread portion of the plug
4) Pull out the core using M4 nuts
5) Mark the drill bit to appropriate length to gauge the depth of the drilled hole
6) Block any gaps and holes where metal swarf should not enter using rags and duct tapes
7) Starting with 6.5mm bit holding it as straight as possible to the direction of the plug drill out to the required depth.
8) Repeat it with 7mm and 7.5mm progressively until you reach 10mm(8mm for thinner stem).
9) At 10mm, you can see the thread portion of the plug separating from the main body.
10) Clean out the thread and hole using hooked pick and vacuum cleaner making sure there are no threads or swarf of plug left inside the hole.
11) Get a 6.7mm(5mm bore for M6) drill and drill into the plug by about 20mm further down
12) Tap M8* thread in the plug 10mm deep, clean well and apply penetrating oil again
13) Get a suitable socket and Long HT M8* screw, washer and an M8* nut.
14) Place socket over the plug and insert M8* screw with M8* nut washer on it.
15) Screw the M8* bolt into the plug and wind up the bolt using the nut
It should pull out easily enough.
* (M6 for 8mm stem glow plugs)