603 Vacuum Pump & Oil Pressure

[markg612]

REFERENCE 603.960/124.133 INSTALL

Brian,

I hope you could weigh in on this.

Based on my assessment of the oil circuit on the 603s it appears the oil pressure could be affected by a defective vacuum pump, especially after it warms to 85°C

Currently, when the engine is cold or first starts even after it's warm, all is well, but once the temps rise to 85°C, the pressure "pulses", at about the same rate as the vacuum pump pulses, also, the heater shifts back and forth between full defrost (default for no vacuum) and normal, again, only after normal temps are reached.

Big Question: Have you ever seen a failing vacuum pump effect oil pressure? Oil pressure is perfect cool or cold but pulses once it's normal. Also, the heater vacuum shifting doesn't happen until normal temps are reached.

Thoughts?

Thanks,
Mark

The vacuum pump is splash lubricated, it can't affect oil pressure.

[Brian Carlton]

I agree.

It's not the vacuum pump causing fluctuation in oil pressure.

I'd be inclined to look at the gauge...........or did you already replace that?

Fluctuating oil pressure gauge 87 300D

[markg612]

Thank worldpac for photos, I would agree with splash assessment

Brian--New parts to include, oil pump, sender, 12 cam followers, all working parts in the filter housing (check valves and thermostat)- No to gauge replacement, it operates perfectly--It does not exhibit the symptoms noted in the link you sent to the other thread.

The only 2 parts left, aside from the main and cam bearings, is the Timing device and the cam chain tensioner, both of these receive line oil pressure. The timing device's cam for the vacuum pump would be the only other "pulsable" item, again, aside from the bearings, that could introduce a variation in oil pressure. Well, the spay nozzles could too, but they would either work or not work, I would think, as opposed to pulsing. (603.960 has the 1 bar pop off nozzles vs. the 970 and aspirated installs that do not.

--So, what about the injection pump timing device? The pressure oil circuit delivers oil to the injection pump and timing device--If the vacuum pump cam's shaft, as there are moving parts inside the timing device were warn from my earlier oil viscosity issue, could this possibly be the pulsing issue?

One other note, whatever is worn and susceptible to the change in oil viscosity due to temperature, it is an item that cools rapidly after shutdown. It only takes about 15 minutes of cool down and restart to see the pulsing momentarily minimized, but returns within a few minutes as the temps come back up to normal.

[Hatterasguy]

Dumb question; but you have hooked up a mechanical guage to confirm that the old questionable guage on the cluster works?

If so what were the readings at hot idle? How much are they jumping around?

[Brian Carlton]

Originally Posted by markg612

No to gauge replacement, it operates perfectly--.

............and we know this because..........????

Gauges are noted for "questionable readings" depending on their damping characteristics.

..........what Hattie said, above.............

[markg612]

Originally Posted by Brian Carlton

............and we know this because..........????

Mechanical gauge revealed the same indications to a T.

The high end of the pulse is the normal pressure at idle, 1.8-2.2 bar. The low side of the pulse is around 1.2 bar. ANY increase in engine rpm dampens the pulse to a minute wiggle until the gauge pegs at 3 bar around 1300 RPM.

Back to the timing device, Brian, have you ever seen wear in the IP timing device? Maybe so worn, it produced a loss of oil pressure that, maybe by the pulsing motion created by the vacuum pump against the vacuum pump cam, with a worn bearing area in the timing device to effect oil pressure?

What about the cam chain tensioner? It also receives line pressure from the oil pump--as mentioned earlier, these 2 items short of the bearings, are the only items not changed out. Again, oil temp has an immediate effect on the presents of the pulse.

Interesting--The IP once it's hot, seems to have a bit of a ticking thing at the same rate the oil pressure pulses. Also, I have a bearing somewhere in the left front area of the engine, most likely the IP that starts to "shutter" above idle from around 1000 up to 1500 RPM before it smooth out. It is NOT coming from the front at all, i.e., idler, WP or PS pump, it's definitely from the side.