Help! W124 serious oil pressure problem

[nmacc]

Hi Folks,

I've a 93 220TE with 185k. Made a 100 mile trip this weekend and noticed upon arrival at my destination that power seemed to have dropped slightly. Also noticed a strange rasping sound at > 3,000 rpm, rather like top-end noise, or (heaven forbid) a broken ring.

When I began the return trip I noticed that the rasping sound was becoming audible at lower revs. After about 15 miles the oil pressure seemed to drop slightly. When I slowed down it dropped away completely to zero, but the oil light did not come on.

Finally made it home at a steady 55, but the rasping noise is much more evident and oil pressure at idle reads zero, rising to just short of 3 Bar at 2,000 rpm.

At all times engine temperature has been low-medium and oil and coolant levels are fine. I can't detect any sign of bottom end rumble and she's not buring any oil.

Any thoughts?

 

[Quick Silver]

Camshaft bearing ? or oil pump impellor shaft bearing ? A broken piston ring will give you loss of power but you would be belching oil smoke out the exhaust . A hard one to decipher ,check your plugs for oil contamination .

 

[television]

Rasping sound could be an exhaust leak, if it reaches 3 on the oil scale when running nothing much wrong there, the pressure sensor may be faulty for it to be zero at idle

 

[nmacc]

Thanks Malcolm, I did indeed think it was a leak at the manifold as it had a tiny crack in the manifold when I got it. I'll check it now in daylight and see if it's spread, but it doesn't sound exactly right for that.

I really do think it's associated with the oil pressure. It could be a gauge fault, but the behavior is very strange: just under 3 Bar at > 2,500 rpm and progressively dropping to completely zero at 1,000 rpm (when hot).

Quick Silver, you may be right with that camshaft bearing.

The power loss is interesting. If there was a reduction in oil flow to the hydrau;lic tappets, could that affect the valve opening to the extent that it would noticeably reduce the power?

Regards

N

 

[television]

No, any loss of oil would not affect the power, any way you do not have any loss at normal running RPM. The gauge will not be faulty but the sender could be out of spec.

With bearings, the are all daisy chained in line through out the whole engine, any one bearing failing and the whole line drops, you have the main gallery, and the feed off for the valve gear, but your running pressure is OK

 

[nmacc]

Thanks Malcolm.

I'm not as confident about the oil pressure as you are! The oil pressure has always been a little strange on this car. When I first got it about 10,000 miles back the pressure had two states: zero when the engine was off and 2.5 Bar when running. Cold or hot, high or low revs, 2.5 Bar. Another noticiable thing was that there was no evidence of top end wear. She seemed to be absolutely quiet, so I wasn't too worried about the pressure.

Then, after a few months and maybe 4,000 miles the oil pressure suddenly started to read a full 3 Bar. But this wasn't all good news as now the pressure would drop a bit when hot. The obvious answer is that the sensor had been a bit faulty and that the fault had cleared and I was now seeing the true pressure. However I'm not sure it was that simple, as I also now suddenly had tappet noise on start-up.

Anyway, to make a long story boring, I've had a look at the patient in the cold light of day and the crack in the manifold has indeed got bigger, but that's not the good news it should be as I can hear what I think hear is some form of bearing noise and I have a noticeable leak from the area of the front crank seal. There's a noticeable collection of drips under the car this morning.

Looks like a major strip down. Now where can I find a cheap, rusty 220 as an engine donor....

 

[roadhog]

No, any loss of oil would not affect the power, any way you do not have any loss at normal running RPM. The gauge will not be faulty but the sender could be out of spec.

With bearings, the are all daisy chained in line through out the whole engine, any one bearing failing and the whole line drops, you have the main gallery, and the feed off for the valve gear, but your running pressure is OK

Don't be too quick to dismiss the gauge. Mine's on the blink and sometimes needs a gentle reminder of where it needs to be.

When was the last oil change? I don't know anything about petrol 124's (or any 124's other than mine for that matter) but on mine it's quite important to clean the pilot hole in the long bolt that goes through the oil filter.

A leaking manifold would give you loss of power.

 

[nmacc]

Thanks Roadhog, I didn't even know there was a hole in the bolt; I'll check it out. She was due an oil change around now and the oil is probably thinner than it should be, but it's still reasonable clean.

 

[television]

The front crankshaft seal is an easy job to fix,just the damper off etc.

With bearings in an engine you cannot hear them as such, sure if a big end has gone it will knock with every firing stroke, mains bearings could rumble, top end camshafts you cannot hear..

I can send you a paper on changing the front seal, the hardest part is torquing up the damper ring / pulley.

For the top end of the engine to be noisy on start up, this would show that the maybe the oil held is running back down, the noise on start up could be timing chain and this is the most common as from say 120k miles and upwards.

The oil feed to the top of the engine runs up the front of the engine, it could all be down to that crankshaft seal.

I was brought up to be concerned and wary of oil pressure, if in doubt about any electronic device, then I always unscrew the sensor and use a real time gauge, to see what is going on.

For there to be 2.5 bar pressure when running and hot, does not suggest a bearing failure to me

 

[nmacc]

Thanks Malcolm,

I'd be grateful for that paper if you could send it. If it's electronic you could mail it to me at nmacc@eircom.net .

You're right of course, the first step has to be a real gauge screwed into the sensor port. I have some gauges, but I wouldn't have the correct adaptors for the thread; do you happen to know the the thread off the top of your head?

I know it seems OK to have 2.5 Bar when running, but the 121 miles we did last night was a bit nerve-wracking, driving a wife & two small children on a rural motorway as the rattle got more noticeable at lower revs. I tried to keep it at a speed below which the rattle began, but that became impossible as the trip when on and finally we could hear it at 40 mph.

The drop in pressure when the revs drop is dramatic, it's possible to drive at 20 mph and have zero oil pressure.

Anyway, enough speculation.

Step 1: Take some real measurements of the pressure.

Step 2: Change the crank seal.

Thanks

 

[television]

The other thing is here that if you never do any long trips very much, then the oil may not be thin enough for the pressure to fall away at idle .

What is it like from cold today.

I can print off the details tonight its a 102 I think

 

[wireman]

There is a pressure relief valve on the oil pumps outlet, it is not unknown for their springs to weaken or break and they can get stuck partialy open, the symptoms can be just those you describe .
Not sure about yours but on many engines is it's in the sump on the oil pump just where you can't get at it without spending a day to do so..
Get a test gauge on the oil sensors port to check out your gauge before you undertake any major dismantling.

 

[television]

There is a pressure relief valve on the oil pumps outlet, it is not unknown for their springs to weaken or break and they can get stuck partialy open, the symptoms can be just those you describe .
Not sure about yours but on many engines is it's in the sump on the oil pump just where you can't get at it without spending a day to do so..
Get a test gauge on the oil sensors port to check out your gauge before you undertake any major dismantling.

The sensor is on the side of the filter assembly, forget these sizes now are they 1/8th gas threads

 

[nmacc]

The bad news

Thanks for the advice on this folks, but the bad news is that it's been diagnosed by an MB Specialist......


It's a big end.


Looks like 220TE RIP. Particularly irritating as I'd put a lot of new bits on this one as I was planning to keep her.

 

[television]

Could you not think about putting in another lump, if the body is good then it is worth it.


Strange how life moves on,20 years back and I would have thought nothing about slipping the engine out and rebuilding it