The Jensen Owners' Club

All, the FF makes a nasty noise, info as follows:

- Tinny, clattery noise with a frequency following engine rpm
- Only comes in once engine is above 80C, and disappears again if tem falls below 80C
- When listening with a rod stethoscope the noise is strong and clear at the rear of block where the valley pan is bolted down with a clamp and three small hex head bolts. Equally strong at the oil pressure low switch right at the rear of the block. And nearly as strong at the very rear of the valley pan itself.
- Oil changed
- Lifters replaced
- Oil pressure is 80 psi cold, ca 45psi hot at idle and 80 psi at say 2000rpm
- Oil pressure needle vibrates a bit at all times, when the clattering is there it fluctuates very quickly with ca 30psi peak-to-peak at idle. With rising revs the frequency increases and peak-to-peak reduces to ca 10psi at 3000psi

Otherwise the engine runs beautifully, idles nicely, pulls strongly, responds well to the throttle.

Any ideas what is happening

Your exhaust manifold gasket is blowing.

Nope, copper gasket and when I pulled it there was no trace of a leak at all. I.e. no tell tale black tracing.

Check the torque converter bolts--they could be loose!

Cracked exhaust manifold or downpipe gasket?

Steve

Per wrote:All, the FF makes a nasty noise, info as follows:

- Tinny, clattery noise with a frequency following engine rpm
- Only comes in once engine is above 80C, and disappears again if tem falls below 80C

- Oil pressure is 80 psi cold, ca 45psi hot at idle and 80 psi at say 2000rpm
- Oil pressure needle vibrates a bit at all times, when the clattering is there it fluctuates very quickly with ca 30psi peak-to-peak at idle. With rising revs the frequency increases and peak-to-peak reduces to ca 10psi at 3000psi

Those oil pressures are in my opinion excessive. You should have 45 - 65 psi when hot at 1,000rpm on an SAE40 grade of oil. Increasing engine speed should not increase oil pressure further, the pressure relief valve should regulate that.
A fluctuating oil pressure needle indicates either a fault in the oil pressure sender or gauge or it really is indicating a fluctuating oil pressure as it builds up and is then suddenly released. A sticky pressure relief valve in the oil pump would give that symptom. You should validate the pressure fluctuation with a directly connected pressure gauge.
But picking up on the location of the noise which seems to be linked to the fluctuations and with such high oil pressure could it be possible that one (or more) of the lifters is venting all its oil resulting in a gap for the push rod until the oil is replenished in the lifter until it squirts out again? If the lifters have insufficient oil there would be a noise on the pushrod. Such an action could cause the sound and could also cause a fluctuating oil pressure as oil fills the lifter and then is squirted out uncontrolled.
It wouldn't do it when cold because the oil is too thick but once it thins out when hot then it could happen. A fluctuating pressure indication could cause damage elsewhere as when the pressure drops momentarily it could lead to a flow reduction and consequent starvation elsewhere.

With the (electrical) oil pressure senders typically installed in our cars, I would be very surprised to see that kind of instantaneous response as described by the OP.

I certainly agree with Chris that you should get a real independent mechanical gauge on it, to confirm what you think you are observing.

Rocky.

The gauge is mechanical, the sensor for the lamp is electrical.

That explains the fast response of the gauge.

Rocky

OK, checked and rechecked since last mail:
- Torque converter bolts tight
- Oil pressure relief spring etc OK

I have revisited the pressures and 45 - 50 psi at idle is just right as is (warm) 80 at about 1500 upwards for 80C temp. (Checked on various mopar forums.)

So:
- Oil pump is at the opposite end of the noisy area.
- When warm the pressure needle flickers a bit but is rock steady at 80psi once rpms are a bit above 1500.
- When oil is hot (water temp above 88C) the noise starts and pressure flicker wildly as related previously.

From this I believe the pump delivers as it should. If it was the pump it would struggle to keep pressure up but needle would not flicker unless the pump was really damaged and then it would give off some sort of noise. If the suction side was blocked by debris (e.g. from the timing gears) I still do not see why that should cause rapid flickering with frequency following engine speed without fail.
Moreover I am now convinced it is a tappet(s) being oil starved or leaking down too fast that I hear. NB! Tappets have been renewed.
Thus there is a leak down somewhere which is pulsing. A natural candidate might be a rocker arm generally leaking a bit and when hitting the oil hole leaking a LOT!? There are no untoward noises so I do not believe the main or big end bearings are the cuprits.

Comments?

Per wrote:Comments?

Your exhaust manifold gasket is blowing.

No, no and no Keith! As I mentioned I have already pulled it and no trace whatsoever on the copper gasket. Anyway It would not start blowing above 88C and immediately stop when below. Particularly not with a copper gasket which has a higher thermal expansion rate than cast iron and steel.

Per wrote:No, no and no Keith! As I mentioned I have already pulled it and no trace whatsoever on the copper gasket.

You're supposed to have TWO!


Can I pop over on Sunday afternoon and listen?
I'm just next-door.

Well yes them not it ☺

You are welcome to listen but depending where you are it is between one hour and two days from Sweden. I can offer a cup of coffee though .....

To rule out exhaust gasket leaks, how about removing spark plugs from pairs of cylinders???
The two back ones on each side, see if the noise changes.