Author Topic: Living with Mazda3 Diesels - 1.6 PCV oil mist  (Read 6165 times)

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Offline The Bun-yip

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Living with Mazda3 Diesels - 1.6 PCV oil mist
« on: March 13, 2013, 03:02:01 PM »
The 1.6 diesel has a curious design flaw with consequences that some find worth managing. The Oil Filler Body mounted on the top of the engine also contains an oil separator and the Positive Crankcase Ventilation valve. Unfortunately the arrangement is not always very successful in removing the oil mist/vapour from the crankcase gases. It is a legal requirement that these gases are piped into the air intake system so that they can be burnt thus avoiding the atmospheric pollution that would result from venting to atmosphere.

Detecting the excess oil vapour problem is simple. Remove the air intake hose that connects the output of the Air Filter from the MAF sensor to the input opening of the Turbo. An inspection of the hose may reveal an accumulation of oil which should be dealt with. The lower temperature of the input air stream has caused the oil vapour to condense. Unfortunately this is not covered by any "Standard Servicing" schedule carried out by Mazda dealers or any Independent garage.

1 Result The result of this contamination may take some time to be felt. Unfortunately the gradual accumulation of oil in the Air Intake system can have serious consequences.

1.1 Turbo ? The ingestion of small amounts of oil vapour by the turbo does not appear to do much harm providing the amount of oil remains small. Should a major engine fault develop which ejects a considerable amount of oil the story would be different but of little concern as the cause of the flood would be the main concern.

1.2 Intercooler Over many miles the Intercooler gradually accumulates a significant amount of dirty oil which reduces the effectiveness of this Charge Cooler so impacting performance and fuel economy. It used to cause significant blockages in earlier diesel cars before high mileages accumulated. I have yet to hear of this causing a problem for these engines.

1.3 Inlet manifold
Similarly the inlet manifold accumulates oil contamination over time reducing performance. It would seem that we may accumulate high mileages before it becomes a major problem. The Polyether amine cleaning products like BG 244 are reported to have a beneficial effect when the presence of the PEA in the exhaust stream is fed back into the inlet manifold via the EGR system. It is a nice theory but I have yet to see any demonstration of just how effective it is. Prevention would seem to be preferable to a cure. The use of C1 oil should also prove beneficial by reducing dramatically the amount of solid matter in the EGR stream fed into the manifold to mix with the oil vapour.

1.4 EGR
The normal presence of burnt oil in the exhaust stream contributes to the build up of 'carbon' that can block the EGR with damaging effects. Once again PEA cleaning products may help to deal with the consequences.

1.5 MAF & Air Filter When the engine is switched off the crankcase gases are no longer being streamed through the turbo and as the engine spools down these gases flow back over the MAF sensor and out through the air filter... backwards.

The air filter gradually accumulates oil on its top surface reducing its effectiveness.

The MAF operates by heating an element which is cooled by the input air stream to generate the signal used by the ECU. The oil contamination results in an inaccurate signal and eventually causes the MAF to fail. Unfortunately a degraded MAF does not usually trigger a fault signal. So the consequences can take some time to recognise. There is a good description of the results here. Faulty MAF sensors can be difficult to diagnose. See:

2 Protection By now you will recognise that it can be worthwhile to protect the engine from the impact of the unwanted oil vapour. When requested Mazda have fitted an oil separator from another model (thought to be a Mazda 626) in an attempt to deal with the problem. It has not been very successful by the accounts I have seen. Two posts on the forum describe in detail how this problem can be dealt with.

2.1 Catch Can
My own attempt to deal with the issue is documented in this forum post. See:

When I costed out the possibility of using a Man & Hummel filter before I built my Catch Can only the 'Provent 200' size was available. The less expensive 'Provent 100' more suited to our 1.6 engine that ukzmisr used was not yet available. It would have been the better choice.

2.2 Filter The most successful method for dealing with this problem is to fit a filter in the CCV stream that is capable of filtering the oil particles out without restricting gas flow. The problem is also faced by diesel engines from many other manufacturers. It is no surprise to find that one of Germany's major filter manufacturers came up with a solution by developing a family of filters for different engine sizes.

The following post by ukzmisr illustrates the installation of the M&H Provent 100 filter.  The forum member “ukzmisr” reports that the filter needed replacing/cleaning after about four months of Motorway driving.

3 Maintenance A simple DIY maintenance task that is not in the Mazda handbook is worth adding to your routine. Open up the Air Filter box and inspect the flat panel filter surface. It should not have an oil stain on its surface. The gradual growth of a stain will reveal what rate of oil contamination you are experiencing, if any. Any visible stain should have you disconnecting the outlet tube and reaching for a can of electrical cleaner spray to clean the MAF mounted on the Filter Outlet. If cleaning the MAF is required I would repeat the procedure at the time of the next service. A standard paper Air Filter should be replaced while an oiled cotton filter (K&N) should be cleaned if a large stain or wet oil is visible on the filter surface. Electrical Contact Cleaner aerosols are widely available. Halfords, Maplin and eBay can all oblige.

3.1 Clean MAF & Air Filter Many diesel drivers now automatically clean the MAF at every service or more frequently. Diesel MAFs have been known to fail in less than 30,000 miles with engine oil contamination being the main culprit. Oil on the MAF can also come from a badly over oiled cotton (K&N) panel filter. This Forum post will show you more on diagnosing and cleaning your MAF.  Unfortunately the original photographs in the post have disappeared.

3.2 Clean Turbo inlet hose Whilst the turbo inlet hose is disconnected from the MAF it is easy to check the state of the hose for oil contamination. You may only find a smear of oil if all is well. If you find oil pooling in the concertina folds of the hose a more through clean to protect the Intercooler, Inlet manifold etc is a good idea.
« Last Edit: March 13, 2013, 03:34:41 PM by The Bun-yip »

Offline Willpower

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Re: Living with Mazda3 Diesels - 1.6 PCV oil mist
« Reply #1 on: March 13, 2013, 05:24:17 PM »
Look at life through the windscreen, not the rearview mirror.
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Re: Living with Mazda3 Diesels - 1.6 PCV oil mist
« Reply #1 on: March 13, 2013, 05:24:17 PM »