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Defender 2.5na loss of power when hot


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Hi All, have an ex army Defender with C reg in front. 2.5 n/a. Have had loss of power(ie it won't go anywhere) when hot recently. Starts fine, but when hot no power! Leave it for an hour till cold, and off she goes no problem! Started with fuel system. Drained tank, checked fuel intake pipe from ther, new sedimenter,lift pipe, filter, and a couple of pipes that were weeping.

I am NOT an expert, or even very good DIYer. Have now removed cylinder head. BUT no obvious problems with head gasket (have had no water loss or water in oil).Plate on engine, says overhauled 1995. Still army I guess.Speedo reads 40+k.

Am now looking at valves and pistons. Some carbon build up, but nothing obvious. No 3 cylinder valves are not as carbonised as others. They look as if they had been burning hotter. All springs etc look normal.

Next step, valves out, perhaps new springs, check valves, seats etc????

Any ideas would be very welcome.

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Hi Ted, I think that your ideas are on the right track by giving it a top end overhaul, sometimes it isn't obvious that the cylinder head gasket is failing. Lap the valves, fit new stem seals. I would also get a set of recon injectors (you can get them on an exchange basis). Ensure that the surface on both the head and block is clean and flat, take the head to be skimmed if necessary. Get a good head gasket such as the one by Elring (part ERR3618g). Make sure the rockers are adjusted when done.

HTH

 

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Since you have the head off, you're half way towards checking for any signs of seizing.  Drop the sump (drain it first!) and remove the bearing caps to check the crank shaft and shells for scoring, and while the big end caps are off, remove the pistons to check the full length of the bores and the piston sides for damage.  Just make sure you lay everything out logically as you remove it - it all needs to go back in the same place and orientation as removed.

I suspect it's a valve or injector issue, but checking the above will at leave peace of mind.

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If #3 looks whiter/hotter then maybe it is an injector problem or even an injector pump problem on that cylinder.

While you have the injectors out you could put them all back on the ends of the pipes and try and point them into a big cardboard box, put some safety glasses on and get someone to crank it over and look at the spray pattern from the injectors (don't get too near the spray)

Also change the hotplugs (ERR1223) in the head while you have it off - they are the little round plugs with a square hole in front of the injectors, they usually crack, see if the one on #3 looks any different?

It's not getting too hot is it? have you checked the rad, water pump, thermostat etc?

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Thank you all for response. Valves coming out tomorrow. The glow plugs I changed about a year ago. The bottom end I will leave for the moment! Will then order up gasket set, going for new valve springs, and valves where necessary. Ted.

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It's your choice, Ted, but to check the bottom end is easy enough with the top removed, and while you can check the crank and bearings with the head in place, you can't check the bores, pistons or rings without removing the head.  It'd be a shame to have to go through the whole faff again, and buy another head gasket, for just a couple of hours' worth of extra work.

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Kevm isn't referring to the glow plugs, but the swirl chambers located in the head.

Personally I think the sound advice given by Snagger should be considered very seriously. It would be a shame to find out later on that there is a problem with the bottom when it is so accessable right now in terms of taking the pistons out to check.

 

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I had exactly this problem with my '84 N/A 90 when I owned it - I didn't approach it in quite the same way as you though. I knew the engine was healthy having changed the head gasket successfully some months previously, and had none of the usual symptoms of head gasket failure (difficult to start, mixed oil in the coolant, overheating, etc) so looked at the fuelling system. It appears that having repeatedly used water-contaminated diesel, it had damaged the distributor pump significantly and when warm would not manage to produce enough pressure. I was lucky that a Lucas CAV trained diesel specialist was a near acquaintance (I was living in rural Ontario, Canada at the time) who rebuilt the pump and checked injectors.

I would be inclined to have the pump and injectors tested, particularly as you don't seem to have found anything in your strip down to indicate why you lose power, assuming from the information you posted that it wasn't actually overheating... I would also heed the advice to check the bottom end at the same time for the sake of a couple of hours.

Also just a word of caution on testing the spray pattern of your injectors yourself, presuming even that you would know a good pattern from a bad one (and I certainly wouldn't). Don't. Leave it to the specialist. A car tyre runs at 2 bar, injectors supplied by a rotary pump are around 150 bar.

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Thank you all for your input. Have just found that my new son in law is a trained mechanic, and had a look at the old head gasket on Saturday when over. He also, said it would be a good idea to look at the bottom end!.Have replaced the inlet valves, valve springs and injectors. Reground in all valves. Even borrowed a torque wrench to make sure head was refitted absolutely correctly. Actually quite enjoyed myself!. VERY amazed when she fired up after 10secs cranking. All seems well apart from small drip from one of the rad pipes. Will let her run for a while tomorrow. Keeping bonnet off for a few days to repair paintwork/rust below wscreen.Then shall try a run. Ted

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Have done a few runs now and all seems well. Starts better, and I think, slightly better performance. Have also cured oil leak from rocker cover, so hopefully no more oil around engine. I only do under 500 miles a year, so bottom end hopefully ok for a while. Am now trying to find the right dashboard warning bulbs. Haven't found the right ones yet. Can the bulbs be replaced in the holder, or do you have to buy bulb with holder?

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The bulbs are independent of the holder.  You might struggle to find them in places like Halfords as they're a bit old fashioned, but a decent independent Autoelectrical shop will stock them.  Otherwise, Vehicle-wiring-products.co.uk will sell them.

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Thank you Snagger. Now have lots of dashboard warning lights working!. Pretty dodgy system, but a bit of wiggling made good contacts. Oil pressure lite still not working, so going to try new switch/sender on engine. ps Had nasty turn other day, loss of power and lots of misfiring and blue smoke.Got home ok ,just, and had a look at engine whilst ticking over. Smoke from 4 injector. Took it out and found that the top body was loose and threaded bit inside also.Tightend all up and re-inserted. All seems good again. Ted

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You said that you renewed the injectors - did you fit reconditioned ones in exchange for your old ones? If so I have never had one loose as you describe. There are two types of washers on the injectors, a larger diameter copper washer that sits under the injecor body and the smaller diameter steel domed sealing washer that sits under the nozzle. Did you replace the domed washer with a new one when you refitted the injector?

The domed washer protect the nozzles from hot combustion gasses and maintains compression. You can get a loud hissing or chuffing sound most notable at tickover if one of those sealing washers are not replaced for a new one.

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I echo Monkie's comment above.

 

Before you replace the oil pressure switch, do a conductivity check of the wire.  It could have got brittle and snapped internally, corroded or, been otherwise damaged somewhere along its length.  A quick test shorting the terminal to the filter housing (might need to scrape a bit for god contact) should show whether it's the switch or the wire.

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