Odd engine activity after an hours drive

[MrBeard]

Subject says it all really.

engines runs nicely, but when we go for a long drive, hour (and half) we get unexpected problems.
On the way to derby, just got off the M1 and we started to get oil pressure buzzers, and the only way to be rid of them whilst driving was to be in a low gear with high revs.
On the way back we were coming in to a local village and windy back roads, we started to get acceleration hesitations.

We do have a very minor accel hesitation occasionally. (hopefully the new rotor arm will help that)
We have previously had lots of issues with buzzer of doom, but many parts replaced and it's fine (except after 1.5 hours drive)

Any suggestion as to where I need to be looking for answers, I considered over heating being the issue, but I had just topped up the water after a broken clip had to be replaced on the water pipes. Unfortunately the water temp sensor on the dash is not working atm so no easy check.

Cheers
MrBeard

[kevtherev]

OK
firstly what engine is it
My crystal ball is on the blink

[kevtherev]

Lets tackle one issue at a time ... for a petrol engine
hesitating acceleration is fuel related and mixture in particular, air leaks on the inlet side is a common culprit.
This includes vacuum pipes to and from the distributor, gaskets and the brake servo hose from the manifold.
hesitation is also caused by wrongly gapped plugs

A weak mixture would cause the engine to get overly hot, an air leak would weaken the mixture

the buzzer would go off because...

The sensor is faulty
The oil and filter are past it and need changing to 20w/50 mineral, and a Mann filter
Oil level is too low
The oil pump is worn

[MrBeard]

Sorry for the lack of van info, I thought I had added it to my SIg. I have now.

So yes, It's petrol, 1.9 Waterboxer DG engine.

Air leaks: the air filter and inlet have recently been fixed/replaced.
Haven't seen any obvious gaps in the vacuum pipes to and from the distributor, gaskets and the brake servo hose.
The hoses are all in good condition, and I have just replaced the distributor (which helped a lot, it really was in poor condition).

"A weak mixture would cause the engine to get overly hot, an air leak would weaken the mixture", Interesting, would that also affect mpg?

Oil level is good and several wires to the sensor have just been replaced and the electronics of the sensor checked. both high and low pressure switches recently replaced.
Oil is classic car 20/50 mineral.

I did wonder about the oil pump when I was having buzzer of doom issues, and it was the next thing to replace if the electronics hadn't fixed the issue.

Hope that helps.

It just seems odd that these issues are only appearing after an hour of driving and if I pull up and let the engine sit (off) for 20 mins it's fine again.

Cheers

[kevtherev]

Unfortunately the water temp sensor on the dash is not working atm so no easy check.

well if it is overheating this would need to be addressed.

My ten pence
further to your information, I would suggest that after 1 1/2 hours the oil temp is at full working temp.
at this temp it is quite a lot thinner in viscosity.
However you grade is good and if the engine was not overheating then I can only conclude the oil pump is not delivering enough pressure at lower rpm's
replacing the sensor between the pushrods (low pressure, blue) with a wet gauge , would check this and confirm low pressure value pressure at full working temp.(above 0.3 bar)
replacing the sensor with a wet gauge at the line pressure sensor point (oil pump) would indicate oil pump efficiency above( 0.9 bar)
If these values prove to be good then there is a fault with either the sensors or the loom or earth connection

a weak mixture would decrease MPG as the engine is working harder and thus ..hotter
this again can be checked at a local garage with a gas analyser. (CO reading should be 2.5%) and a high O2 reading would indicate an air leak.

[MrBeard]

a weak mixture would decrease MPG as the engine is working harder and thus ..hotter
this again can be checked at a local garage with a gas analyser. (CO reading should be 2.5%) and a high O2 reading would indicate an air leak.

Well I have had the garage check the mixture and that was ok. he didn't give me reading but i asked enough questions to make sire it was OK in all direction!

As for the oil pressure (petunias!) Oh no! not again! More messing about with the oil pressure sensors.

[ermie571]

OK
firstly what engine is it
My crystal ball is on the blink

tried getting parts?!
Been waiting for parts for mine at work for years....on back order apparently. Means I have actually gotta do the bleeding work!!

Em
xx

sorry as you were.....

[kevtherev]

have you been on the wine Em?

[Aidan]

it's not a case of messing about with sensors it's a case of testing the oil pressure using a wet gauge and checking that it is actually producing enough oil pressure, and then if it is, it is a simple case of testing the wiring for the bod circuit so that you are no longer getting erroneous bod warnings
the procedure in Bentley manual for testing the bod system is straightforward, it isn't rocket science, simple logic

[kevtherev]

Agreed a wet gauge is the way to go
I fitted one permanently and disconnected the buzzer

[MrBeard]

Agreed a wet gauge is the way to go
I fitted one permanently and disconnected the buzzer

Sounds great, any chance on more detail, what do you mean by wet gauge?
Do you mean this: Oil Pressure Gauge, 2 5/8", S/Comp, 150Psi Or this sort of thing?

how easy is it to fit?

[kevtherev]

Yes. . Often called a mechanical gauge.
I used demon tweeks.
I used a gauge in psi.
Things you need are
A T piece to connect the low pressure switch and tubing to the low pressure socket (m 10 X 1)
a suitable mechanical gauge
and about 6 metres of tube.

[jamesc76]

Ages ago when I had one of those cak vw engines ( ) i had the same problems of buzzer going once engine and oil were hot, turned out the be the seat of the oil pressure relief vale was worn, I used a lot of cunning to get round it, but might be worth checking the spring length and that the ball bearing and seat are clean and no scores or grooves in it!

[MrBeard]

Ages ago when I had one of those cak vw engines ( ) i had the same problems of buzzer going once engine and oil were hot, turned out the be the seat of the oil pressure relief vale was worn, I used a lot of cunning to get round it, but might be worth checking the spring length and that the ball bearing and seat are clean and no scores or grooves in it!

We replaced the oil pressure release valve (or rather put one in as it was missing when I bought the van) also new washer, but didn't do the spring. I thought that oil might have been leaking from there fore a bit but after we changed a clip on a pipe the oil leak stopped, so I think it was just a convenient collecting and drip point.

[Ian Hulley]

but after we changed a clip on a pipe the oil leak stopped

Now which clip on what pipe would that be ?