KAD. Low pressure when coming back to idle

[BruceK]

I am hoping it is a faulty sensor or connection wiring issue but my port engine is running at the lower extreme of pressure range once up to temp and for a brief moment below when coming back to idle after running hard. (20kpa and 45kpa instead of 30kpa and 60kpa on my starboard)

However I ballsed up last maintenance round when on replacing the oil cooler o-rings to sort out a minor oil weep I used a bit of blue Hylomar on the mating surfaces and it went and hydraulic-ed the o-rings out causing me to dump a lot of oil in the bilge. (The engine never ran dry of oil though, just from top of oil stick to min mark). I replaced all o-rings again and the set includes what I believe is the oil pressure release valves o-ring which I replaced as they were there and I had the o-ring.

Shortly after I was also plagued by an overheat issue which was resolved with replacing the impeller. The boss it was determined seemed to be slipping. No visible damage but replacing it worked so...

This clouded my mind to other things but it's since then that the oil pressure has been lower than normal.

My turbo bearings being slightly stiffer than Farsco's rebuilt unit and Porto's injection of woe has got me thinking I may indeed have an oil pressure issue rather than old wiring or sender issue.

I need to validate my oil pressure first obviously but am I correct in thinking parts 2 through 8 or pressure release valves? Are the springs liable to weaken?
Where would you start to check for a low oil pressure problem if it is verified. No knocks or anything from the big ends and the engine runs as sweet as a nut, it should, it's already been through a major rebuild 6 yrs ~ 300 hours ago.

 

[BruceK]

Sorry KAD42A

 

[Momac]

Is it an easy job to swap the sensors over between the engines to check if it is a sensor issue.

You mention an overheat . The raw water pump face plate should remain cold with the engine running. If not the pump may be worn but rather than replace the whole pump at great expense a wear kit is available at relatively modest cost. Or the brass face plate may be replaced at modest cost.

 

[rlw]

One thing to bear in mind is that wire/connector corrosion causes temperatures to read higher and oil pressure to read lower. Some forum wisdom I picked up years ago after my engineer and I tried to fix a problem that was not there. Worth checking before doing a lot of other stuff.

 

[andy59]

I would check pressure with a mechanical gauge before anything else just to prove that the actual pressure is ok .

 

[East Cardinal]

Have you got genuine part oil filters?
Copy oil filters have caused this low pressure problem, and fitting genuine parts have resolved.

 

[vas]

I would check pressure with a mechanical gauge before anything else just to prove that the actual pressure is ok .

+100

a couple of WIKA analogue gauges one 4bar (air/water) one 30bar (oils -engine gbox) are always onboard with various 1/8 and M10x1 couplings to fit in various orifices and test what's going on...

I'd start there (OK, I'd swap senders first as it's easier...) although I doubt it would read ok under power and mess it returning to idle

cheers

V.

 

[BruceK]

Have you got genuine part oil filters?
Copy oil filters have caused this low pressure problem, and fitting genuine parts have resolved.

Yes Genuine filters.
Oil cooler is genuine but not original to KAD42A. A replacement upgrade to an obsolete part

 

[BruceK]

+100

a couple of WIKA analogue gauges one 4bar (air/water) one 30bar (oils -engine gbox) are always onboard with various 1/8 and M10x1 couplings to fit in various orifices and test what's going on...

I'd start there (OK, I'd swap senders first as it's easier...) although I doubt it would read ok under power and mess it returning to idle

cheers

V.

It reads about 10-15kpa low throughout with a brief drop to 20kpa low after running long and hard returning to idle. For about 5 seconds. The latter almost certainly because oil is hotter / thinner than normal

 

[BruceK]

One thing to bear in mind is that wire/connector corrosion causes temperatures to read higher and oil pressure to read lower. Some forum wisdom I picked up years ago after my engineer and I tried to fix a problem that was not there. Worth checking before doing a lot of other stuff.

Thats what I am hoping. My temp senders / guages read about 8C hotter than a IR thermometer shows at the sender and thermostat

 

[vas]

Thats what I am hoping. My temp senders / guages read about 8C hotter than a IR thermometer shows at the sender and thermostat

sorry if I'm teaching you what you already know but,

get a permanent BLACK marker pen, and paint the are you want to test, you may be surprised how higher the ir meter will go.
the "at the sender" is a bit iffy, where do you aim the IR thing? should be on the block of metal next to where the sender bolts to, not the body of the sender itself, right?
Thermostat body should be okay (if painted black that is)

Obviously the above is pointless as far as comparing the two engines, just useful regarding dif from sender to gauge.
Hope it's the cables (or more likely a ground, trace the sensor cables back?)

cheers

V.

 

[BruceK]

Yes to the metal / engine casting, no I haven't painted it black. Mind you I have a white skin and pink tongue and and a calibration against myself shows I'm fit for work. I'll paint a black dot on for next test though.

 

[Portofino]

Thats what I am hoping. My temp senders / guages read about 8C hotter than a IR thermometer shows at the sender and thermostat

Another dimension to add is this , it’s relative to VP sender Vs gauge discrepancies.
The harness
Yup over time the insulation is heat effected and increase resistance so throws false readings
Sensor is new or swapped, gauge new or swapped then direct connect new bits with new wire and you get a true reading .
I had a temp gauge issue read higher than the IR gauge .
Experienced SoF VP engineer on KADs arrived at that conclusion.

If so answer is accept it - false readings or new harness .
This work hardening and temp degradation of the VP loom insulation comes on with age .

You chase your tail .

 

[Mr Googler]

I found quiet a bit of corrosion in the 16 pin harness plugs at both the engine and behind the dash.

A cleanup improves my volt meter by nearly a volt!

Be warned, they can be a bugger to plug back together unless the pins are perfectly lined up

 

[BruceK]

I found quiet a bit of corrosion in the 16 pin harness plugs at both the engine and behind the dash.

A cleanup improves my volt meter by nearly a volt!

Be warned, they can be a bugger to plug back together unless the pins are perfectly lined up

Exactly where would one find these connectors to the engine loom? i.e. how long is the engine loom. I ask because I have looked and my engine looms disappear into cable conduit and some wires just magically appear behind the dash and no matter how hard I look I have been unable to find them. Knowing the rough length of them would be a helpful start

EDIT: My dash was never a Volvo dash - it was designed for Mercruiser and so it's non conformist. I dont have any connectors at the dash end. Just signal wires coming out the conduit and then a bus system

 

[Mr Googler]

Exactly where would one find these connectors to the engine loom? i.e. how long is the engine loom. I ask because I have looked and my engine looms disappear into cable conduit and some wires just magically appear behind the dash and no matter how hard I look I have been unable to find them. Knowing the rough length of them would be a helpful start

EDIT: My dash was never a Volvo dash - it was designed for Mercruiser and so it's non conformist. I dont have any connectors at the dash end. Just signal wires coming out the conduit and then a bus system

The engine plug goes into the side of the black box above the injection pump.

If it’s a non Volvo dash, there might not be a plug behind the dash.

 

[BruceK]

OK, That makes sense. I know where that connector is, I thought there might be another before the dash before it goes through the conduit as you'd really struggle getting a plug into the conduit. Also where the conduit is in the engine room has a large internal diameter and at the dash a much smaller internal diameter. There is a junction or break off somewhere behind all the panelling where I was expecting to find another connector. .... Maybe the dash one... ???