Replace a Defender 90 / 110 2.5 petrol engine with a Discovery 200tdi engine | Landyworld

Replace a Defender 90 / 110 2.5 petrol engine with a Discovery 200tdi engine

Replace a Defender 90 /  110 2.5 petrol engine with a Discovery 200tdi engine

The 2.5 petrol engine fitted into early Land Rover 90 / 110 isn’t too bad but it doesn’t compare to the 200tdi in the later defenders. The defender 200tdi engine would probably be a much easier fit into the early 90 / 110 but are expensive and difficult to source. The discovery tdi engine is cheap and there are loads of old Discos too rusty to pass an MOT and whole cars are changing hands for under £500.

The following information is about how I fitted a discovery 200tdi engine into my 1989 2.5 petrol 110. The process should be identical to fit a discovery 200tdi to a Land Rover 90. I am no expert, this is what I have done and although I have tried to cover everything , it is not meant to be a replacement for knowledge, common sense or mechanical ability!

First of all I stripped the discovery. I am not going to go into how to remove the engine, I assume you can manage that or refer to a Haynes manual. Before you remove the engine, I would suggest you remove the viscous fan unit. I didn’t and it would have been a lot easier if I had! As well as the engine, you need to keep all hoses (water and air), radiator (radiator mounting frame as well), intercooler, fuel filter (remove with pipes – cut them as long as you can), all ancillaries (starter, alternator, pas pump, pas pipes. Also cut the wire to the glow plugs as long as you possibly can. Looking back, I should have removed the transfer box as well!  These three pictures show the discovery 200tdi engine being removed ready to use in the conversion!

Discovery 200tdi engine still in situeRemoving discovery 200tdi engineengineoutdiscoYou should end up with a collection that looks something like this!tdibitsDiscovery 200tdi engine












As you can see, I left all the pipes attached, in fact I left everything I could!  









110frontpanelThe next step is to remove the petrol engine from your 90 / 110. This is made much easier by being able to remove the radiator, grill and slam panel in tact. This is only a few bolts plus undoing the cable from the bonnet release catch and unplugging the horn.

2.5 petrol engine and 200tdi discovery engine ready to replace.







Again, keep all hoses and pipes. I suggest you cut the fuel pipe to the carb, leaving the other pipes still secured to the bulkhead for the moment. If you are as forgetful as me, it may be worth labeling the plugs on the wiring. There aren’t that many wires, just the Alternator, Starter motor, Coolant temperature sensor, oil pressure switch and ignition coil. Next you need to drain your fuel tank and be sure it is completely free from petrol. Mine has a drain plug in the bottom that makes draining nice and easy. I left this out for a few hours with the filler cap off as well; this should let enough of the remains evaporate off.

Once the two engines are out and along side each other, the fun begins! You need to remove the engine mounts and brackets from both engines. The discovery ones are no use and can now go in the bin (or maybe eBay….). The brackets from the petrol engine need to be bolted to the 200tdi engine block. You can possibly use the rubber engine mounts from the petrol engine but there are different part numbers for the petrol and diesel engines so I figured the diesel ones would be more robust. I bought the ones listed for the 2.5td from paddock spares. They were approx £2.50 each (2 needed) and worth replacing at this point because I would imagine that changing them after the engine is fitted would be a bit on the difficult side. The coolant temperature sensor removed from the petrol engine fitted straight into the 200tdi.

At this point I would suggest you fit a new clutch kit. I bought an AP driveline (formerly borg and beck) kit from paddock spares. Take my advice and replace the rear main oil seal (I didn’t do this the first time, it went a week later and I had to take the engine back out…). This is also a good time to change the timing belt etc but I knew the history of my 200tdi engine and knowing the belt was less than 3000miles I didn’t bother. The discovery exhaust front pipe is no use, it needs to be removed. 

There are a few studs / dowels on the tdi flywheel housing that don’t have corresponding holes on the 2.5 petrol bell housing. Some people say you should drill the bell housing, tap new threads etc. I just got the old angle grinder out and removed them. I intend to drill the bell housing holes so I can get bolts into some of the holes at a later date.

With this done, its time to put the discovery tdi engine in. I found it awkward to line up with the box and the engine mounts. What seemed to work for me is to unbolt the driver’s side engine mount and bracket from the block, line up the nearside and the gearbox then bolt the removed mount back on at the end.

Discovery 200Tdi engine being fitted to defender

Once the engine is in and bolted in place the real conversion work begins. You can now refit the wiring! The oil pressure switch fits as it used to, coolant temp sensor fits the same. The wire that used to run to your ignition coil on the bulkhead can now go to the stop solenoid on the diesel pump. The alternator wiring will be slightly different to when you removed it from the discovery. You will need to crimp some eyes onto the end of the cables. The extra wire that was connected when in the discovery was for a rev counter so don’t be surprised that you have one less wire to fit! You fit the two thick brown wires together on to one terminal and the smaller one (battery warning light is separate). As I am writing this from memory I can’t be more detailed, I will take a picture and upload it at some point shortly!

At this point I concentrated on getting the front end back together. It’s best to use the discovery radiator and intercooler complete in the frame that holds the two together. If you want to use the original 90 / 110 radiator you would have to find a separate oil cooler or bypass it in some way! The problem is that if you fit the discovery radiator frame to the brackets on the 110 front chassis cross member, the radiator sits too high and the bonnet wont close.

Defender radiator frame too high

This is how I resolved it.  You need to cut these side bits off because they are in the way.  Dont throw them away yet though, they will come in handy later!


Cut the top piece and hole off the brackets on the cross member. I removed 28mm from them and then welded the top bit back on. Be careful to try and get the hole in the same place (only lower of course) because if you go too far forward the grill etc won’t fit. This picture is the finished article (well before i covered it in waxoyl of course).


Once the frame is in place you will see there is nowhere to locate the original radiator top mounting brackets. On the 90/110 / defender the offside one also holds the bonnet prop and is therefore quite important. Take the studs from the brackets you cut off the side of the frame and weld them onto the top in the correct place. It should then all fit together almost as before!

Please note on this picture its not crooked as it looks, I just hadn’t seated it properly on the bottom mount.

Please note on this picture its not crooked as it looks, I just hadn’t seated it properly on the bottom mount.

Now you will need some oil cooler pipes. Some people have been known to bypass the oil cooler but I figure land rover fitted it for a reason and who am I to argue! I ordered oil cooler pipes from a 200tdi defender (the discovery ones aren’t long enough but your local hydraulics company such as pirtek may extend them for you for a fee). The part number of at least one of the pipes was ESR281 but unfortunately I cant find the number for the other one I bought! I bought them from (and would highly recommend) the Land Rover Orphanage they were very helpful in working out which cooler pipes were the right ones for the job, something my local land rover dealer couldn’t manage.

When it comes to the pipe work there are probably many different ways of doing it. I don’t know if the way I did it was the best way (probably not but it works so here goes…). I used a mix and match of radiator hoses to get it all connected up. I can’t remember which bottom radiator hose I used but I know that on the upright hose to the tank I had to extend it. I cut it and pieced in a bit of steel pipe. I used the steel pipe that runs across the top of the petrol engine and goes to the rubber heater hoses. I also used a bit of this steel pipe to extend one of the heater hoses and twist it so it connects back up to the 110 heater.


I was lucky enough to scrounge a few hoses and bits from another 200tdi disco. I used one full intercooler top hose, a piece of steel pipe (think it may have been exhaust) as a sleeve insert and then half another top hose to make it reach. This doesn’t look pretty but it works and I cant see it causing me any hassles in the near future. You may notice that in the pic below I still have a viscous fan unit but minus the blades!! This is because I didn’t remove it while the engine was in the discovery. Its much harder to get off when you cant lock the engine by leaving it in gear! Leaving it fitted makes getting the engine lined up a lot more difficult because it hits the top of the steering box, hence I cut the blades off! I removed it properly at the end!


The bottom intercooler hose is much more difficult due to its location! Its right up against the inner wing. Some people cut the inner wing (I didn’t fancy that). For the moment I have used a 90degree silicone elbow which I cut down slightly to fit (I am pretty sure this came off the discovery). It is squashed slightly which isn’t ideal but I will replace it when I find the right piece of silicone hose.

I might even buy the kit from eBay for sale by this bloke bought my exhaust front pipe from him (more info later on) and he was extremely helpful and I was impressed by the build quality. I am sure the intercooler pipes will be just as good. His certainly look nicer than mine but I was on a tight budget!

I used the discovery air filter housing but as yet have not located it anywhere properly. I have got it in under the nearside wing top (nice tight fit but added a few cable ties to be sure) where it will remain until I get around to moving it to a more permanent location.


Power steering pipes are the next bit of fun! The low pressure feed to the pump from the 2.5 petrol engine (mine already had power steering) will reach the 200tdi pump. The high pressure connection was different so I had to use a discovery pipe. This isn’t the best of fits (it’s a bit short) but with the odd bend here and there it reaches and for the moment, it works. It doesn’t look like a nice neatly routed factory fit pipe but it’s functional!


The next thing to worry about is the fuel pipes! Although many people will tell you otherwise, the 2.5 petrol engine does have a fuel return pipe. To the right of the place the ignition coil used to be there is a chamber type bowl with fuel hoses coming into it. There is a main feed pipe, a small pipe that feeds the carb and a return pipe to the tank. The thicker pipe is the main fuel line, the thinner one is the return. It’s probably worth marking them up now before you remove them and take this chamber off the bulkhead (another item for the bin). See picture below for location!


Once you are clear of all petrol & fumes its time to mount the fuel filter housing to the bulkhead. I suppose the neatest way would be to drill a few holes and weld a captive nut to the inside of the bulkhead. Not fancying removing the dash to do this I took the scruffy option. I welded the nuts to the outside of the bulkhead. With a few extra washers on the bolts it tightens up nicely and seems secure. I connected the fuel hoses on the car to the ones I left on the engine using rubber fuel hose from my local motor factors. This isn’t expensive and if you experiment with sizes you will find some that’s a real tight fit. Once this has a jubilee clip on I have had no problems at all with it either leaking diesel or drawing in air!

This picture shows the fuel filter mounted and the pipes after I joined them.


So, you have now connected oil cooler pipes, radiator and heater hoses, air hoses, power steering pipes and all the necessary wiring. I am not going to go into detail on filling up fluids, bleeding power steering etc as I assume if you intend to attempt this conversion you are capable of all that! Get some fuel / water etc in it and start it up! At this stage, like me you probably have no exhaust front pipe, no wiring to your glow plugs and no radiator fan. None of that matters, you need to hear it run just to make all the work feel worthwhile…..!

Next step is fitting the exhaust exhaust front pipe. The discovery 200tdi engine is slightly different to the defender 200tdi and the exhaust front pipe is one of the major differences. Its a very tight fit between the starter motor, the chassis and the bulkhead! There are a few options as I see it. The 1st option is to make your own. I know it can be done but it looks like a nightmare with no form of template available anywhere. I figured it would take me best part of a day and as I am always short of free time I decided against it. If, like me you decide to buy one there are only two options left as far as I am aware. You either buy a steve parker front pipe (google it) or you buy the one for sale from

Although this is not the nicest looking of the two, the price difference more than makes up for that. The pipe arrived with instructions, clamps etc and came very quickly. Although I am no engineer I can tell nice welding when I see it! This is one very well made front pipe. I am more than happy with the pipe and with the service from the seller. He seems like a decent bloke (and a damn good welder / fabricator) selling quality front pipes for sensible money. I wouldn’t hesitate to buy another from him should I ever need one.

If you decide to buy one of these you will get (included with it) a set of much more comprehensive instructions than I am capable of writing so I will just give you the general outline. I removed one of the studs and used a bolt instead, its almost impossible to get the front pipe over the 3 studs with the engine in! There is a clutch pipe on the bulkhead that is in the way, this needs to be cut away from the bulkhead. There is a fair amount of movement in the pipe once its free. Slide it closer to the wing by a few inches and weld it back in place. Here is a picture of it moved and ready to weld.


Once this is welded you can fit the front pipe.  There really is not a lot of spare room here!


The next bit ( a smooth bend also supplied in the kit) can be made to meet your existing exhaust with a bit of adjustment. Its worth mentioning at this point that you shouldn’t use the standard petrol exhaust system. I believe its too restrictive and the excess back pressure will damage the tdi engine / turbo. You can buy a tdi exhaust system but as I had lots of exhaust pipe lying about I decided to make a side exit exhaust. I will write this up separately once its neat enough to show in public!!

The obvious remaining bits are the glow plugs and radiator fan. There are much nicer ways of doing this but once again I wanted simple and more importantly (to me anyway), cheap! I have added two relays under the bonnet and wired them up. I have a flick switch for my radiator fan and a push button for my glow plugs. I just hold the glow plug button in for 10 seconds and then turn the key! Its worth mentioning that it seemed to start quite happily without glow plugs, it even started perfectly one morning whilst covered in snow! As for the radiator fan, I ripped one from a scrap rover 25 and have got it in place temporarily. I might need something bigger in summer but for the moment I am yet to even turn this fan on. These engines don’t need a fan apart from in extreme heat or under heavy load (towing, offroading etc).

The difference in power is amazing. It now pulls like a train! The only thing I would say is the gearing is now far too low. Its off the mark like a rocket and revving too high at 60mph. If I had thought about it I would have removed the discovery transfer box and fitted that. Oh well, another time maybe!


I wouldn’t like to attempt this without access to a reasonable range of average tools + a welder and an engine crane.

If I missed anything you want to ask, or if you have any comments feel free to contact me by email! Good luck and enjoy!

Leave a comment