1997 Mazda MPV Symptoms of rocker arm issue?

RHOWARD

MEMBER
1997 MAZDA MPV
6 CYL
4WD
AUTOMATIC
150,000 MILES

For a while we have heard a knocking sound while driving which gets faster as we accelerate and assumed it was the infamous mpv lifters knocking. Since we have been faithful with timely oil changes we assumed it was still the lifters ticking. However, a friend who heard us drive up one day said it sounded like a rocker arm problem. Last week we were on the freeway when the knocking became very loud, we lost compression and barely made it to an exit (no shoulder on the highway because of snowdrifts) where the car died and smoke was billowing out of the hood which appeared to be black (assuming oil). Are these symptoms of a rocker arm failing and if so could it have caused major engine damage in the process? The car still acts like it will turn over to start but we don't want to do any further damage. Any advice would be much appreciated.

Saturday, January 3rd, 2009 AT 1:38 PM

3 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi rhoward,

Valve lifters and rocker arms are almost the same, the work next to each other with the lifters pushing the rocker arms.

From the description of the symptoms, it does not look like it is caused by the lifters or rockers arms.

If you have black smoke, something is burning and it could be the wire harness. Oil would not burn with black smoke unless there is a big fire and if it is coolant leakages, steam would be the result.

It is not easy to access what is the cause or resultant product without understanding what had caused the engine to stall.

If it is rocker arms which had failed, to drive further would not cause much problem but still not advisable to drive because if 1 cylinder is misfiring badly, it would cause damaged to the catalytic coverter resulting in it heating up red hot after some driving.

Since the vehicle is not starting now, you should try to isolate the source.
1. Ignition or electrical fault. Check for sparks at plugs.
2. Fuel. Test for fuel pressure at fuel rails.
3. Check if the timing belt is still intact and working.

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Saturday, January 3rd, 2009 AT 7:55 PM

RHOWARD

MEMBER
3 POSTS

We will check the things you suggested in the morning.

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Saturday, January 3rd, 2009 AT 8:29 PM

HIPPO800

MEMBER
29 POSTS

Kind of late.
Rockers should never make sound.
You should check the diameter of the rocker shafts.
Usually, the rocker arm bores only have negligible wear.
The rocker noise is caused by excess clearance between shaft and rocker.
With resultant poor oil pressure to the hyd. Ash adjuster. It will not pump up.
Lifters need good oil pressure to pump up, even the old style big lifters.
Consider that you are putting 150 hp on an engine crankshaft with only 4 main bearings.
Hmmn. Works though?

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Wednesday, February 3rd, 2010 AT 9:41 PM