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Nissan Serena/Largo CD20T Timing Belt and Water Pump replacement and other tips on faults

Upper timing belt cover, crankshaft pulley & bolt
lower metal timing belt cover

frontal pic of the Nissan CD20T engine
1973cc Diesel Turbo

Zexel Diesel Pump

Since no information could be found on the web on this engine. I've posted some tips, hints and photos to make this large job a little easier for the home mechanic/avid DIY'er.


1. Don't be lead down the path to think this is a 4 hour job, or even an 8 hour job. I'm no mechanic but I do know most the parts and their functions in this engine and it can take a few full days to get right.

2. Numerous reports on the web say this job is easy. I'm sure on some cars it is, but on these cars it's not. For a knowledgeable mechanic with all the equipment at his diposal maybe it is, but for your average home mechanic expect to spend a few weekends on it at least.

Why does it take so long?

1. Very limited Space, making it akward to get bolts out and btw you need a battery of socket wrenches, sockets, screwdrivers to tackle this job.

The fact that this engine doesn't have a radiator immediately in front of the engine is probably its only advantage.

2. The main outcome of not having enough space is that it makes it really tricky to get long wrenches in to provide the necessary torque to loosen a lot of these bolts. Some come off easily, others make you wish you had never even started the job in the first place.

Put simply these are basic steps:

1. Undo the 4 bolts on the upper plastic timing belt casing

2. Loosen alternator belt by undoing the 2 bolts on cast steel idler pulley.

3. Loosen a/c compressor belt by undoing bolt immediately under the compressor itself.

4. Undo 4 bolts on water pump (located at 9 o'clock when looking at the engine front on). This belt also runs the power steering pump. Don't touch any of the bolts on the p/s pump as I did. You could end up with oil leaking everywhere.


If you don't do this the belts can squeak and loose traction. Additionally if the alternator belt slips (as mine did) this will cause the hydraulic system on the rear brakes to fail which is potentially very dangerous.

5. There are now a myriad of bolts to take off. Get a mirror in there and check you haven't missed any. They should come off the cast metal piece which has the alternator idler on it, the waterpump and the lower metal timing belt cover.

6. Use the 1 1/8" socket on the big bolt on the crank shaft and use the engine cranking method described on other web sites.

7. Now the metal cover, cast metal piece can come off and you should be left with complete view of the entire cam belt, tensioner and idler.

8. Line the engine up to TDC. Using correction fluid mark out a few points on the camshaft part of the belt and on the crankshaft. You must have a minimum of 2 points (one on each).

9. If you can get the tensioner off with an allen key this makes getting the cambelt off quite easy. After an hour or so of trying I couldnt, even with a metal extender on the allen key. I took off the 3 small bolts on the camshaft and took off the metal circular cover and slid the belt off gently with a screwdriver.

10. It is easy to take the water pump off now (either to check or replace). Undo the 3 bolts and it should fall off along with its gasket. Check for any rust. If there is any use sandpaper to cut it out and then repaint over it. While the pump is out also check that the fins are not damaged and the bearings run freely.

11. When your ready to install the water pump back grease either sides of the gasket then pop the 3 bolts back in. To be continued when time permits.....

Other problems that have been fixed since I got this van:

Tachometer dead:

This was solved by grounding a red/black lead which comes out of the bottom LHS of the Zexel Diesel pump. Don't bother checking the tachometer itself as these units are pretty reliable. If this doesn't work try using a multimeter on the back of the speedo cluster to check to see whether the voltage changes with engine speed. It should be a linear relationship ie increase in rpm = increase in voltage.

Brake light on or on/off with intensity of the light changing:

1. Firstly check the brake fluid level is between MIN and MAX. Next breifly check the switch on the handbrake and make sure the parking brake light changes intensity when its on and off. If still not fixed it will most likey be bad contacts on the brake pressure switch which is located on the LHS under the front passenger seat. It has one tube going into it and an one electrical input into the bottom of it. I presume that this switch creates a closed/open circuit with the handbrake switch. Anyway, unscrew the 2 small bolts holding it in place and clean the copper contacts thoroughly. This should fix the brake light so that it only comes on 1. At startup and 2. When you've got the handbrake on.

Some Pics:

Water pump

Rusty Waterpump

Longitudinal Nissan Serena Engine

Cast steel bracket which has alternator pulley attached