Td5 D2 engine - EGR / Exhaust Cooler

A while ago I removed the EGR valve from HX. That was an easy and well documented modification helping the engine to breath more clean cooler air which all helps with the internal combustion.

Removing the EGR valve leaves a handful of 'open' vacuum lines that need to be plugged or removed entirely. The opening and closing of the valves is controlled by vacuum pressure which is supplied by the vacuum pump that is mounted on the front of the alternator.

Failure to block-off these vac lines can lead to failure of the brake-servo which also uses vacuum pressure from the pump. This is a safety critical concern and must be competently addressed.

HX is a '15P' Td5 with the additional fitted exhaust cooler mounted on the front of the engine directly in front of the cylinder head. In the following diagram, the exhaust cooler is labelled '3' and the fluted pipes either side connect it to the exhaust manifold on one side and the EGR valve (1) on the other. Part no.18 is the equivalent pipework on a non '15P' TD5

As well as having to seal the end of the cooler which has a direct feed from the hot exhaust manifold, the cooling function of the unit is provided by its built in water jacket connected by pipework to the engine cooling circuit. These coolant supply pipes need to be removed and the integrity of the cooling circuit must be maintained. Simply plugging their ends is not enough as that will only create 'dead' ends in the cooling circuit flow.

Two views of the exhaust cooler removed from a TD5 engine. The small bore connections for the water jacket can be easily seen and the last photo even shows the flimsy plastic pipework that I needed to replace. 

Sections of the factory fitted pipework used to service the exhaust cooler are made from a thin bore plastic that in time will just go brittle, crack and fail causing loss of the engine coolant and potentially cooking the engine.

I know this from experience as it was the first problem HX threw at me. I was tracing the source of a coolant leak and was shocked to find that the pipe was plastic and alarmed at how it just cracked under finger pressure!! I had to swap out a section of it with some rubber hose and even now it remains thus... 

It was always my intention to remove the exhaust cooler water pipes and that led me to an investigation of the routing of the cooling system pipes on the TD5 engine and to plan how to re-route the piping. Well that was a few years ago and the time has come to revisit that idea.

Rave is pretty good at describing the engine cooling system and even has diagrams of the differing systems and a very handy 'flow' diagram that displays the directional flow of water through the pipework.

Using these diagrams it is easy to see that the modification requires the exhaust cooler inlet and outlet to be connected together to effectively by-pass the exhaust cooler. The only question is where and how to do this .....

In the above diagram, the 'euro 3' 15P engine cooling system is shown while inset 'A' shows the original configuration. Part no.6 and 39 have the same function being the metal pipe that is attached to the rear of the engine block and fed by the oil cooler mounted below the turbo. Part 37 is a shaped rubber pipe running from the end of 6 direct to the inlet on the exhaust cooler 34. This pipe needs to be re-routed to connect to the coolant reservoir where 36 is shown to connect to the coolant reservoir.  This pipe, 36 is the thin brittle plastic one prone to failure.....

Figure it's best to use rubber hose for this but there is some tight bends to be made so raiding the spares box for suitably shaped lengths of hose is a must.... Not a hundred percent sure of the bore measurements, they look like they are different at each end but that is easily overcome with adaptors.

The above diagram from Rave shows the directional flow of coolant through all the pipework on both versions of the TD5. 

Apart from the obvious difference with the exhaust cooler install, careful study reveals differences in the radiator and coolant reservoir as regards the pipework attachment points. It is not possible to convert a 15P engine cooling system to the earlier cooling system without changing the radiator and coolant reservoir to match...  This should be born in mind if any spares are needed in the future..

Finally for now, a shot from the Web showing an exhaust cooler on the front of a TD5 engine. The fan has been removed along with the rocker cover and the injector harness. The black circular plug on the cylinder head immediately behind the exhaust cooler is the source of an oil leak on HX , but that's another story ..

Another blog deals with what happened when Hx started leaking coolant from the exhaust cooler return pipe and how I fabricated the by-pass hose discussed above...