Mondeo Mk3

The Mondeo manifold saga

I've run Fords for a good few years, first Sierras and later Mondeos.

These have been generally been reliable, economical and good performers - until now.


Mondeo Mk3 2L Duratec engines can eat their inlet manifolds

I'm not sure exactly what year this was fixed (if ever), but the earlier Mk3 engines have parts in the inlet manifold which can wear out, eventually become detached and be sucked through the engine, with possibly catastrophic results (ie. new engine required).
[A re-designed manifold was introduced sometime around 2003, which has better bearings on the swirl plates. I do not know for sure it this is a 'cure' to the problem, or just has a somewhat longer life before failure.]


In my case, the final failure happened one morning as I started the car in the garage, so it was only running at tickover for a few seconds after the manifold bits went in to the engine and it seems no serious damage was caused to the piston or valves.

I'm probably one of the lucky ones, I'd only spoken to a few people about it before someone said it had happened to them while driving and in their case the engine had to be replaced.


What actually fails

The inlet manifold has an extra set of butterfly valves set in to the flange where it attaches to the cylinder head. These are controlled by a vacuum actuator and appear to be designed to deflect the airflow towards the fuel injectors to give better mixing under low throttle / high manifold vacuum conditions.

The problem is that each butterfly has relatively small moulded-in bearing bushes at the ends, and over time these wear away. Once the bushes are worn through, the long square steel spindle that runs the length of the manifold (to connect the butterfly plates to the vacuum actuator) also starts to wear away at the points it touches the manifold tube walls, and eventually breaks at one or more of these points.

In mine, the steel spindle was in four seperate pieces, one of which was in number three cylinder.

This was only the final failure. Two of the butterfly plates were rattling about in the inlet ports and one of these still had another bit of the spindle in it, with the ends nicely rounded over purely due to it bouncing about against the port walls.


Update: For further details on diagnosing the fault and removing the manifold, read these articles on www.fordmondeo.org / www.fordwiki.co.uk

Inlet Manifold Diagnosis
Inlet Manifold Removal

Also, one of the other fordmondeo.org users (CoC) has posted some excellent photos of the two different butterfly or swirl plate designs in this thread: New and Old style butterfly plate photos

Note: replacement butterfly inserts are now available for the new type manifold - see the upper picture in the new/old link above.

I have not used these myself, but according to reports on the Mondeo forum, they will directly replace the butterfly assemblies on the original type manifold. They apparently do not relate to the old manifold in the Ford part database, presumably as they were not intruduced until after the original manifold was discontinued.

A set of these is a fraction of the price of a replacement manifold, but do check that the metal spindle and actuator etc. are still in good order before fitting them - a new manifold is cheaper than a new engine!


The pictures - click an image for a larger view

(For reference, the car is was just under six years old & had always been serviced by a local Ford main dealer)



Manifold - 1

This is the manifold, as removed. As you can see, two of the butterfly plates are missing - they were in the head ports


Port 1

This is Port 1, the butterfly plate is out at one side but the stub of spindle (towards port 2) is stopping it falling out completely.


Port 2

This is Port 2 - in this one the spindle had broken completely at both sides of the butterfly plate, and the plate complete with shaft was in the head port.


Butterfly with shaft

You can see quite clearly the way the spindle has been rounded over at the ends - this must have happened a long time ago, it's just luck that this particular bit of metal didn't get into the cylinder.


Port 2

Port 4 - A straight bit of spindle! This is the longest piece of the spindle, it's still straight and slides freely about in the manifold. When one of the other bits has broken away, it's slid 'forward' and allowed the butterfly plate to drop off intact.


Butterfly plate

The butterfly plate from No. 4, found in the inlet port.


Port wear

This is a view of one of the ports, showing the crater that started out as a bearing hole for the bush on the end of a butterfly plate.


Port closeup

A close-up of the same thing..


Port 2

The set of inserts that support(ed) the butterfly plates, plus the bit of spindle from port 1.


Port 2

A closer shot of the shaft from port 1.


Port 2

This is the side of a butterfly assembly, clearly showing the wear of the hole and bush.


Port 2

And it's close-up view.


Port 2

And the crunch - this is the bit of spindle that ended up in the engine.
As you can see, it's almost 50mm long.

When I assembled the other parts of the spindle, it was obvious some was missing.

I retrieved this with a bit of magnet fishing down the plughole of number three cylinder.


Port 2

Looking at how mangled that bit of steel is from just a few seconds at tickover, it's not surprising the engine can be wrecked if this happens on the road.

After fitting the new manifold, the car runs fine - actually better than before, which is not really surprising as it's no longer got stray bits of plastic partly blocking the inlet ports...

The compression readings are excellent and virtually identical on all cylinders, so I think it's safe so say that neither the valves or piston rings were damaged.


If you need any more info on this, you can contact me via the Mondeo Enthusiasts Group forum (username rajenkins). Or, as a last resort, email me

Page last updated January 2010
Copyright Robert Jenkins 2007 - 2010
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