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Old 10-06-2021, 04:46   #1
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Perkins 4108 high oil pressure

Hey all -

I have a new to me 4108, the ďnewĒ (Perkins language) model engine with a Bowman combination header/exhaust manifold, a gear oil cooler and a remote oil filter installed.

Iíve had to do a good bit to the motor already, the water pump">raw water pump started leaking shortly after buying the boat; I pulled the hx core and seawater pump to renew, and found erosion damage and a pinhole in the hx tubestack sleeve as well as scale and indications that there was raw water ingress into the coolant side of the system (the hole in the tubestack being the primary indication, obviously). The new tubestack will be installed today or tomorrow.

The raw water pump was found to be out of alignment with the drive shaft, it displayed deep scoring on the pumpshaft, a new jabsco pump has been installed and the adapter plate removed and re-centered using the brass alignment tube. I have scrubbed and flushed the header tank through to the cylinder block drain with the hx core removed, and will be running phosphoric acid through both sides of the system once its back together and I can more effectively flush and circulate fluids through the motor (I canít find my crappy hand pump, so Iíve been siphoning through from the header tank to flush out debris in the coolant lines using my mouth and a tube, itís super disgusting).

The oil and filter were changed within 60 engine hours from now, and the oil was just changed yesterday. Not very sludgy, but definitely dark. At the first change, I pumped oil through the dipstick, yesterday I pumped both through the oil pan access port as well as the dipstick. The oil pressure runs high very quickly ó I am not sure that it still does as I canít run the motor until I have the new hx core installed, but I have a suspicion that the issue is either a clog somewhere in the oil system, or a sticking oil pressure relief valve.

Itís my understanding that thereís little chance of access to the 4108 pressure relief valve as itís located in the oil pump. Is there anything I should do to further diagnose the high pressure source, or a good way to flush/clear the oil lines? I was planning on doing frequent t oil changes if the problem continues to appear, in an attempt to flush clean oil through the lines. If thereís anything obvious (or subtle) I might be missing, Iíd love to hear about it ó lots of help online with low oil pressure, but info on high oil pressure seems to be fairly scarce.

Iím by no means a diesel mechanic, so anything that anyone might be able to suggest would be wildly helpful. Iím delivering my new boat up the coast to the northeast and had to stop to remedy the cooling issues. It would be very nice to get home.

Cheers all!
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Old 10-06-2021, 04:59   #2
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Re: Perkins 4108 high oil pressure

I'm not a diesel mechanic, either. Let's go with your hypothesis that the problem is a clog somewhere in the oil circulation, and that it is a problem worthy of pursuit.

Consider what you could check. You've got a remote oil filter. It and the tubes too and from it could be the source of the problem.

Can you temporarily install a second gauge? differential pressure would help you isolate the area with the problem.

Can you blow out the oil system, preferably backwards, so as to knock out a blockage?

If there is a blockage, it's on the pressure side, with the blockage between the pump and the pan. Of course, that's 90% of the system.
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Old 10-06-2021, 05:10   #3
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Re: Perkins 4108 high oil pressure

That’s kinda what I was wondering, whether there was a good way to blow through the lines..I figured this was a pretty standard move, but despite some searching couldn’t find good instructions on how to do it, maybe I’m missing something really obvious, I’m going to keep looking.

Barring further info from this post, I was planning to pop off the oil filter lines and just blow air through them and reattach — but I’m not sure whether I then have to prime the lines to the filter. I assume the answer is yes but I don’t know enough about how air moves through/bleeds off lube oil lines to know whether that’s true, or how to do it. I’m sure I can find that somewhere though. The only reason I haven’t yet is just not wanting to accidentally introduce some sort of airlock somewhere, even this relatively basic lube system is more complex than anything I’ve ever really worked on.

I don’t think I can install a second gauge, I am pretty limited in what I can do where I am in terms of part sourcing, getting the hx core was a pretty tricky maneuver.

Thanks for your help.
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Old 10-06-2021, 06:17   #4
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Re: Perkins 4108 high oil pressure

Would try an engine flush to remove built up sludge, etc. from the oil/pan.


A better explanation here.
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Old 10-06-2021, 06:34   #5
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Re: Perkins 4108 high oil pressure

Before you work too hard on this, but SURE your measurement is correct. A lot of oil pressure gauges read LOW resistance as LOW pressure and high resistance as HIGH pressure. A loose or corroded connection at the sensor, or anywhere else in the system, can look like high pressure on the gauge…
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Old 10-06-2021, 06:49   #6
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Re: Perkins 4108 high oil pressure

That engine flush thing is exactly what I was looking for. Iíll keep an eye on the problem, try to verify my gauge reading independently, and if the issue persists I will flush the motor.

Thanks guys!
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Old 10-06-2021, 07:07   #7
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Re: Perkins 4108 high oil pressure

Quote:
Originally Posted by BillKny View Post
Before you work too hard on this, but SURE your measurement is correct. A lot of oil pressure gauges read LOW resistance as LOW pressure and high resistance as HIGH pressure. A loose or corroded connection at the sensor, or anywhere else in the system, can look like high pressure on the gauge…

Bill's idea to look at the sender is a good one and quick. Would pull the sensor wire off and clean as needed for a good contact.

Since you have no history w/this motor, would flush oil system by doing a couple of oil changes or the flush. This was a recommendation from a Perkins mechanic when we purchased our boat w/a 4.236 and been working well since then.
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Old 10-06-2021, 07:23   #8
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Re: Perkins 4108 high oil pressure

What is "High"?
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Old 10-06-2021, 07:40   #9
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Re: Perkins 4108 high oil pressure

Here's a SWAG, noting that I do NOT know the Perkins 4108, so take with a lot of salt:

Some Perkins were repurposed British engines, with the blocks coming from gas engines. These engines had their oil pumps driven by the distributor drive gear. I suspect that the drive gear is still used, with the distributor mount simply capped off. If this is the case, then pulling the cap/blanking plate may give you access to the drive gear. This will pull out easily and you can then drive the pump with a long large flat screwdriver. Connect one to a drill motor and you can use the pump to pressurize the oil system without running the engine.
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Old 10-06-2021, 07:56   #10
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Re: Perkins 4108 high oil pressure

High oil pressure meaning pegged gauge. Not immediately and not constantly, so itís not only the gauge (though could still be the sender, for sure).
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Old 10-06-2021, 07:56   #11
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Re: Perkins 4108 high oil pressure

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Originally Posted by Cheechako View Post
What is "High"?

Good point and will also ask what weight oil are you using?


Oil pressure for the 4.108 is 30-60psi at max rpm and normal operating temp. A higher viscosity oil will increase oil pressure.
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Old 10-06-2021, 08:01   #12
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Re: Perkins 4108 high oil pressure

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Originally Posted by Kevin Spacebag View Post
High oil pressure meaning pegged gauge. Not immediately and not constantly, so itís not only the gauge (though could still be the sender, for sure).
They run very high when first starting up cold, but mine was never pegged. I would probably do nothing but test the gauge/sender until you can run it and get it good and hot. See what it is then.
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Old 10-06-2021, 16:01   #13
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Re: Perkins 4108 high oil pressure

If you have an external oil filter or an oil cooler just be aware that for some engines there is a one way valve built into the filter mounting. The valve ensures the oil flow is behaving. However, if the tubes (hoses?) to the filter mounting are incorrectly attached to the filter housing (i.e. wrong way 'round), then the valve will prevent any oil flow and could lead to either a zero reading or a really high value depending on where the gauge connection is made in the oil flow circuit. For an engine mounted filter this problem can't exist, but for external filters it MAY happen. I have an old Ford 590 E series engine and this was an issue when considering an external oil filter. Can't say for the 4108's.
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Old 10-06-2021, 17:17   #14
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Re: Perkins 4108 high oil pressure

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Originally Posted by billgewater View Post
If you have an external oil filter or an oil cooler just be aware that for some engines there is a one way valve built into the filter mounting. The valve ensures the oil flow is behaving. However, if the tubes (hoses?) to the filter mounting are incorrectly attached to the filter housing (i.e. wrong way 'round), then the valve will prevent any oil flow and could lead to either a zero reading or a really high value depending on where the gauge connection is made in the oil flow circuit. For an engine mounted filter this problem can't exist, but for external filters it MAY happen. I have an old Ford 590 E series engine and this was an issue when considering an external oil filter. Can't say for the 4108's.
Good point, and if the wrong filter is on it, some have no valve or etc....
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Old 10-06-2021, 17:44   #15
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Re: Perkins 4108 high oil pressure

You can buy a mechanical oil pressure gauge for about $20. Screw it into the port the sender is in and then you'll have a real reading to talk about. A plugged oil line is extremely rare. I'd bet the gauge reading you saw is wrong and the engine has normal oil pressure. A mechanical gauge will verify it.

Engine oil pumps are closely matched in capacity to what the engine needs. So extreme pressures are difficult to achieve without a custom pump. The rear main seal on a 4108 is an old style rope seal. At high pressure they leak badly.
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