W212 OM651 E220 Coolant Leak – Fuel Filter Housing – Common Problem

Whilst this problem is not just limited to the E Class, it is certainly a common problem on the OM651 engine.

Many a time we come across the customer complaint of coolant light coming on, but no obvious leak. There are a few usual suspects, namely the coolant pump or thermostat housing, but one of the more common ones was to find the leak coming from the fuel filter housing.

Your initial thought may be how does the fuel filter housing relate to a coolant leak? You’re certainly not the only one! This housing has coolant run through it.

After a coolant pressure check and finding coolant around the inlet manifold area, you can be pretty sure that there is an issue with this housing.

This housing is bolted to the cylinder head with 3 bolts, but also to the inlet manifold. As the inlet manifold receives boost pressure from the turbo, the manifold moves upward. In addition there is the continuous cycle of getting hot / cold. Over time this causes the gap between the head and the cylinder head to increase or the housing to crack. Eventually it leaks.

Our good friends at Mercedes Benz actually released a TSB for it. GI01.30-P-058933. See Here.

Parts Required

Thankfully it’s not a terrible job to do. It does require the removal of the EGR cooler, there is a gasket for this that must be replaced. Mercedes have released a new version of this, although there isn’t any specific info on the changes, I would imagine that the new version takes into account for the manifold moving under pressure. Aftermarket ones are available but for the few quid’s difference, its really not worth it in my opinion. Parts required as follows;

Guide to replacement

Click pics to enlarge 👍

Remove vacuum reservoir;

Remove cylinder head cover trim
Unhook coolant hose from holder
Unhook vacuum line in brake booster (5) on vacuum reservoir (6) (arrow)
Detach vacuum hose (1)
Mark vacuum hoses (3)
Mark vacuum hoses (3) and unclip at vacuum Installation: Observe marking on vacuum reservoir (6) and detach
Remove screw/bolts (2) and remove vacuum reservoir (6)

Remove EGR Cooler

Clamp off coolant hoses (1) on exhaust gas recirculation cooler using a clamp
Remove coolant hoses (1) on exhaust gas recirculation cooler
Remove screw/bolts (2) from exhaust gas recirculation cooler
Undo screw/bolts (3) and remove bracket (4)
Remove screw/bolts (5) and exhaust gas recirculation cooler

Remove Fuel Filter Housing

Unclip fuel filter with lines still connected and place to one side
Remove cover (A) from holder (B)
Unscrew holder with temperature sensor (C) and place to one side
Unscrew holder (D) for fuel lines and remove
Detach coolant hoses (E)
Unscrew connection fitting (F) and pull out of coolant hose (G)

Install in reverse order!

Add coolant, run up to running temperature and bleed cooling system.

Ideally, check and clear any fault codes.

Any questions, please do not hesitate to contact me, il do my best to help!

Notes

Couple of things to note, and i quote this from the TSB;

‘It is absolutely essential to install the coolant connection fitting together with the new seal provided, and to tighten the bolts in the sequence below.
– Tighten the two bolts for the two-hole flange on the cylinder head first to 10 Nm.
– Then tighten the three bolts for mounting onto the intake manifold with 8.5 Nm.
The use of lubricant and sealing agent is not permitted!’

For diagnostic reasons the vacuum hoses must not swapped around.

Torque Specs;

Bolt, support brace for vacuum reservoir and exhaust heat exchanger to Y-support brace – 9 Nm
Bolt, vacuum reservoir to vacuum reservoir bracket or vacuum reservoir support brace and exhaust heat exchanger – 8 Nm
Screw/bolt, exhaust heat exchanger to valve housing – 9 Nm
Screw/bolt, support brace for vacuum reservoir and exhaust heat exchanger to Y-support brace – 9 Nm
Screw/bolt, exhaust heat exchanger support to exhaust heat exchanger – 9 Nm
Bolt for