excessive oil pressure on fresh engine rebuild

toycort
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excessive oil pressure on fresh engine rebuild

Postby toycort » Sun Aug 06, 2017 10:14 pm

I just rebuilt my 4age, new pistons, cams and oil pump. Upon start up the oil pressure gauge pegged at 100psig and the oil filter gasket blew out dumping 3 quarts of oil in 20 seconds of runtime. I installed another oil filter and watched it swell and stretch as I increased rpm to 1500 and the gauge was pegged at 100. I suspect the oil pump relief valve is not releiving. Has anyone experienced this problem? It is an Asain pump. Any ideas of what else the problem could be?

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Sun Aug 06, 2017 10:49 pm

Have you checked to see if you are getting oil to the cams ?

Cheers... jondee86
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toycort
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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Sun Aug 06, 2017 11:11 pm

Yes, I ran the engine with one of the cam covers off, it appears I am getting oil but I have never done this before so I dont know if the volume is correct.

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Mon Aug 07, 2017 2:29 am

I don't know what the quantity of oil would be going to the cams, but there should
be oil coating everything. When the engine is idling and you take the oil filler cap
off, droplets of oil should be flicking out the filler and making a mess :)

The spring loaded relief valve in the oil pump normally will only open at high rpm
when the pump is flowing more oil than the engine can handle, and pressure gets
high. At idle it normally will be closed. Your oil filter should have a bypass/relief
valve built-in to allow oil to get to the bearings if the filter element gets clogged
and creates a high pressure drop.

Oil pressure is a measure of the resistance to flow... the tighter bearing clearances
are, the harder it is to force oil thru the gaps, resulting in higher pressure. To get
100psi at idle should not be possible, because as you say, the oil pump relief valve
should open... IIRC it opens at something like 75-80psi.

The fact that you are over-pressurizing a new filter is also strange, unless you had
a filter without an internal over=pressure relief valve. Even so, to get that much
pressure at idle or just above, suggests that there is unusually high restriction in
oil flow to the crank and cams.

Got to ask this... what kind of gauge are you using ? I am assuming some kind of
aftermarket gauge, so electrical or mechanical ? Does the needle move when you
turn the ignition ON ? And does it go immediately to 100psi when you start the
engine, and drop straight back to zero when you turn the ignition OFF ? Or does it
take a few seconds to hit 100 and maybe a few more seconds to drop back to zero
when you turn the key OFF ?

Cheers... jondee86
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toycort
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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Mon Aug 07, 2017 8:28 am

I have an after market electric gauge. The gauge builds pressure over a few seconds after the engine is started and bleeds off when the engine is stopped. I was using this gauge before I rebuilt the engine and it acted normal.

Years ago I had a similar event with the oil filter gasket blowing out. Turned out I overshimed the relief valve spring preventing the excess pressure being dumped.

Tom

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Mon Aug 07, 2017 2:52 pm

I guess anything is possible. Did you shim the relief valve on the new pump ?

The oil pump is a positive displacement type, so a new pump with fresh oil and
starting from cold could generate decent pressure. But as outlined above, the amount
of pressure is determined by the resistance to flow. Resistance to flow varies as the
square of velocity (gross over-simplification) so that normally the relief valve would
only come into play at high rpm where flow is much increased.

That is the curious thing :? It is like you have an obstruction to flow somewhere in
the system. If you want to experiment, remove the sparkplugs, disable the EFI and
ignition by pulling fuses, and spin the engine on the starter. See how much pressure
shows on your gauge. Then put the plugs back in (still with fuel and ignition disabled)
and crank it again. See if there is any difference in gauge readings.

Cheers... jondee86
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toycort
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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Mon Aug 07, 2017 4:37 pm

Before I fired the engine I cranked the engine with out plugs. If I remember correctly it was 60 pounds using the starter. I'm in the process of pulling the engine to access the pump and check the relief valve piston.

Thanks for your feed back, I'll let you know what I find.

FYI This engine is in a 65 mk1 cortina.

Tom

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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Mon Aug 07, 2017 11:08 pm

Engine is out and pump is off. I removed the relief valve spring and it took 80 pounds of air to unseat the piston. I inspected the piston and reinstalled it in its bore and it would hang up sliding in the bore. I reinstalled the spring and tested it with air.. It took 100 pounds of air and several attempts to get the piston to move and relieve the pressure. Tomorrow I'll work on the piston to bore fit to improve it sliding in the bore.

I'm not convinced this is my only problem. I'll look at the bearing ports and check my main and rod bearings.

thanks

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Tue Aug 08, 2017 12:17 am

Ahh... I think the piston is supposed to slide in the bore under its own weight, so yours
might have got jammed with a bit of flash from the pump casting ? Anyway, good find
and since you have it apart well worth checking bearings for any clues as to why oil is
having a hard time getting back to the sump.

Image

Back in the day these were racing with 100hp at the rear wheels, and considered quick :)

Cheers... jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby Rogue-AE95 » Tue Aug 08, 2017 3:21 am

toycort wrote:It is an Asain pump.


Makes me think that it's worth disassembling and inspecting a brand new Aisin oil pump, if one is being used for a build, to make sure there are no issues like this. I think there was some talk here previously about Aisin (OEM manufacturer) vs Toyota oil pumps.
'88 Corolla All-Trac

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Re: excessive oil pressure on fresh engine rebuild

Postby davew7 » Tue Aug 08, 2017 4:56 am

Are you using aftermarket head bolts? They sometimes restrict the oil flow to the clylinder head. The kits typically have one bolt with a reduce shank and under head radius for the oil port location. Dave W

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oldeskewltoy
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Re: excessive oil pressure on fresh engine rebuild

Postby oldeskewltoy » Tue Aug 08, 2017 7:13 am

pressure relief should come @ 57psi

Image


The small relief valve piston should move freely.


The only engine I've ever seen distort, and then blow a filter off, was an refurbished 289 Ford, with a high pressure oil pump (not sure why the builder used a high PRESSURE pump??)
OST Cyl head porting, - viewtopic.php?f=22&t=300

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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Tue Aug 08, 2017 8:22 am

Thanks all for the feed back. I'm using oem head bolts. I'll inspect the bearings today and look for more issues.

Tom

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Tue Aug 08, 2017 3:10 pm

toycort wrote:I'll inspect the bearings today and look for more issues.

The stuck piston in the relief valve explains why you were showing 100psi on your
gauge, but it does not explain what caused the pressure to go that high. Thinking
about it, the only explanation I can come up with would be if the main bearing
shells either had no oil holes or the shells were installed upside down.

That would mean no oil to the crank and high oil pressure. Kind of unlikely but still
an assembly error that crops up from time to time. This hypothesis does fall into
line with your recollection of around 60psi while cranking the engine.

Cheers... jondee86
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toycort
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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Wed Aug 16, 2017 10:22 pm

I finnaly figured out how to use the new site.

I pulled the engine and oil pump. The relief valve piston was stuck and needed 80 psi air with the spring
removed to unseat the piston. There was debris in the bore and the piston was rusty. I cleaned the bore and polished the piston so it would move freely in the bore. I reassembled the spring
and it would open about 70 psi on the bench. I pulled the crank and ensured all the bearings were lined up with the oil holes in the block. I removed the oil galley plugs and everything
checked out ok. Engine is reinstalled and running in car. I did the 30 minute cam break in procedure and after the engine warmed the oil pressure was 70 psi at 3500 and 25 psi at 1200 idle.
I used 5-30w oil after draining the break in oil. I'm seeing 90 psi at 4500 rpm. I hope it drops as it breaks in, I only have 20 miles on it.
This still seems too high. I will remove my electric gauge and use a mechanical gauge and see what that shows.

Any ideas?
thanks

Tom

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jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jondee86 » Thu Aug 17, 2017 5:59 pm

I only use the OEM dash oil pressure gauge in my car, and it hits the 3/4 mark on
cold start and drops to around 1/2 when fully warm. When driving it sits between
1/2 and 3/4 and I don't remember ever seeing it go past 3/4. So that makes me
think that the relief valve is holding the max pressure to 3/4 whatever that means :)

If you tested with air and the valve actually opened at 70 psi and prevented the
pressure from going any higher, then obviously it was working on the bench. Oil
has a higher viscosity than air, so I might expect the pressure to go a little higher...
say to 75 psi. And that should be the highest pressure anywhere in the system.

So how you can get 90 psi is a mystery :? From a mechanical point of view the only
explanation would be if there was something preventing the valve from opening far
enough to pass sufficient flow ito relieve the pressure. Or possibly if there was some
restriction in the oil return/bypass path downstream of the valve. Failing that we
could look at the "possible but improbable" reasons... such as excessive crankcase
pressure.

Cheers... jondee86
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Re: excessive oil pressure on fresh engine rebuild

Postby jdm86gtz » Sun Aug 20, 2017 5:28 am

I get about 90 psi max on 2 of my 16v engines (6kg/cm2 on gauge) both with the later type AE92/101 pumps.
I think when cold around 50-60 psi and around 30 psi at idle when up to temperature.

toycort
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Re: excessive oil pressure on fresh engine rebuild

Postby toycort » Fri Aug 25, 2017 9:03 pm

I finally got around to installing a mechanical gauge. After driving and putting 30 miles on it I installed the mechanical gauge in place of the sending unit for the electric gauge. At 1200 rpm idle 20-25 psi, any rpm above 3k 75psig. So I am going to assume my electrical gauge reads high. I have nearly 100 miles on the rebuild and the pressure seems to have dropped a few psi. I'm going to call it acceptable for this engine and just keep an eye on it.

thanks for your imput

Tom

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