XJ6 & XJ12 Series I, II & III 1968-1992

Bypass Valve for oil may be clogged

 
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Old 01-13-2009, 11:04 PM
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Default Bypass Valve for oil may be clogged

My oil pressure guage is at zero running and the red warning dash light lights up. If I rev it to 2k it goes off. Oil is full, and a mechanic said it could be a clogged oil bypass valve. It is between the filter housing and the pan?
 
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Old 01-14-2009, 01:12 AM
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Default RE: Bypass Valve for oil may be clogged

The oil pressure relief valve is inside a small cylindical housing, bolted onto the oil filter head.

I would be very concerned about what you have described. Gauge reads zero or flaky, no big deal: the transmitters fail all the time. Light coming on, no big deal, the senders fail and leak all the time. Both indicating low pressure at the same time, and reading higher pressure at higher engine RPM, is a pretty good indication that your oil pressure is dangerously low. The light switches off at 7p.s.i, that's not much of a pulse if it's still on and is accurate.

If it's more that 40 degrees F where you live, put 20W50 oil in your engine and see if the symptoms change. Colder then that, 10W40... and nothing thinner then that, ever.

If necessary, next step is to temporarilyconnect a mechanical oil pressure gauge to see what is really going on. If the pressure is low, your guy can then inspect the pressure relief valve while you cross your fingers. Dead oil pressure on a 4.2L six is more likely from worn crankshaft bearings than anything else.
 
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Old 01-14-2009, 01:10 PM
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Default RE: Bypass Valve for oil may be clogged

Yikes, I am concerned! I use 5W-30, that could be part of the trouble I guess. Should I drain out a quart and put in some heavy weight gear oil?
 
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Old 01-14-2009, 01:53 PM
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Default RE: Bypass Valve for oil may be clogged

'Scuse me?
 
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Old 01-14-2009, 05:15 PM
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Default RE: Bypass Valve for oil may be clogged

allright, not a good idea. just checking for the simpli easy fix.....the easiest fix in the long run is to do the job correctly I suppose. Thanks Jagtech
 
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Old 01-15-2009, 11:14 AM
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Default RE: Bypass Valve for oil may be clogged

Walter,

get 9 quarts of Castrol 20W50 at Walmart and a new oil filter, preferably the Jaguar filter from the Jaguar dealer. After the old oil is drained and new filter installed, add 8½ quarts to the engine. Do not use anything but 20W50, unless freezing, in which case you can use 10W40.

check the oil pressure again.

If problem continues, replace the Sender, mounted on top of the oil filter Head, (the aluminum casting bolted to the block, and to which the oil filter is mounted),The Sender has 1 wire connected to it by spade terminals. Not easily seen from above. It's about time anyway for a Sender replacement, as in 25 years old.

If that doesn't cure the problem, then remove the Bypass Valve and clean it in gasoline, reinstall it making sure it is correctly seated.

You can also do it all at the same time in a different way:

1) drain the old oil and remove the old filter.

2) remove the 4bolts attaching the Oil Filter Head to the block.

3) pry off the entire Oil Filter Head assembly, the gasket will tear apart.

4) take the entireassembly to a mechanic or to the Jag dealer to replace the
Sender,have themclean the Bypass valve, andget a new gasket.

Then reinstall it with everything fresh.

This is not a difficult job to do, but it is messy, so make sure you place a large pan under the work area, a plastic residential Water Heater pan works great and is cheap to get at Home Depot or Lowe's or ACE Hardware. You will have to raise the front passenger side of the car to do this, so like always, make sure you have plenty of support under the car.

Jose
 
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Old 01-16-2009, 09:43 AM
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Default RE: Bypass Valve for oil may be clogged

OK Jose, last night I went outside and pulled the bypass valve. It was clean as a whistle absolutely free of anything. Today I will go pick up at the store the 9 quarts of Castrol 20w50 and a filter (unfortunatly a non Jaguar, but the best ORileys Auto had for the car) and a new sending unit. Ill post back after the oil change and new sender. By the way I have 5w40 in the engine right now. That is probabally why things are going as they are.............
 
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Old 01-16-2009, 09:47 AM
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Default RE: Bypass Valve for oil may be clogged

make sure the sending unit is the right one for the 4.2 engine.
 
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Old 01-16-2009, 05:55 PM
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Default RE: Bypass Valve for oil may be clogged

Fresh oil (Castrol 20 W 50) and a new filter seems to have done the trick! The sending unit is small, it looks smaller than the original. I just got it at the parts store that sold me the oil, it isn't Jaguar. It was only 3.99. Where can I get the real thing? Thanks Jose.
 
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Old 01-16-2009, 06:36 PM
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Default RE: Bypass Valve for oil may be clogged

that's good news Walter!

I would install the real sender right away, the OEM Jaguar sender.

check with Ken or JTO here in this forum. They will have it but it's going to cost
more than $3.99, some parts should remain original and they will cost more.

Out of curiosity, what is the part number and brand for that sender you got at O'Reilly's ?

I'm going to get one forsubstitution-testing when mine goes kaput.

Jose
 
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Old 01-18-2009, 04:26 PM
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Default RE: Bypass Valve for oil may be clogged

Jose,

My oil pressure is good, but the idiot light is still on. I havent driven it to see if it stays on, but I have a test drive planned for this afternoon. The non oem sending unit is the BWD S320. The threaded part is small (in my estimation), probabally about 6/8 of an inch wide. It has some brown goop painted on the threads, is that a lock tite type of a product? Any way, I dont even know if this is the right part, I am having my mechanic attempt to install it Tuesday. I will also have him put a guage on the block to really check the pressure, and Ill hold my breath and cross my fingers......
 
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Old 01-18-2009, 05:15 PM
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Default RE: Bypass Valve for oil may be clogged

Remember, and just to clarify, there's an oil pressure switch for the warning light and an oil pressure sending unit for the gauge.

For $3.99 you probably got a switch, and since your warning light stays on even though you show good pressure, that sounds like what you need.

Cheers
DD
 
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Old 01-18-2009, 06:48 PM
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Default RE: Bypass Valve for oil may be clogged

Thanks Doug! My pressure stays around 40 pounds, but when I parked it got below 15 pounds.......When I drained the oil I only got 7 quarts in the block, and the dipstick shows full. I guess I still have a quart and a half of 5w 30 sloshing around in there. I did a new filter as well. How do I position the car to get a total drain out of the oil pan?
 
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Old 01-18-2009, 07:05 PM
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Default RE: Bypass Valve for oil may be clogged

Walter,

you position the car level to drain all the oil that's drainable.

The fact that you only got 7 quarts out doesn't mean there's 1.5 quarts still in the engine, in any case it means you were low on oil. You did remove and replaced the old filter, right?

How much did you put in?

You could have the wrong dipstick, it's known to happen. check the oil after the engine is shut down.



40 lbs. is normal pressure for the engine. That is what my gauge shows too.
 
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Old 01-18-2009, 07:09 PM
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Default RE: Bypass Valve for oil may be clogged

The drain is on the right, as I recall....so elevate the left side a bit higher. You'll never get every last drop out of the engine, and the filter will hold half a quart or so.

OIl pressure spec is 40 psi at 3000 rpm with a warm engine.

Cold engine/higher rpm= higher pressure, hot engine/lower rpm= lower pressure.

If the engine is hot and just running at idle speed, the pressure may drop down to 5-10 psi, and then come back up when the engine speed increases.

A cold engine may have 40 psi at idle and 50-60 psi when the engine speed increases.

Cheers
DD
 
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Old 01-18-2009, 08:48 PM
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Default RE: Bypass Valve for oil may be clogged

Doug, I never get more than 40 pounds of pressure even at higher rpms. Obviously, worn crankshaft bearings are a worst case scenerio. If that happens to be the case, would I get to 40 pounds of pressure like I have seen on my guage? Is the fix simply a new crank? To pull the motor, and swap out the crankshaft I am over my head, and I bet a shop would charge into the thousands. Ill just pray that is not the case.
 
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Old 01-18-2009, 08:53 PM
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Default RE: Bypass Valve for oil may be clogged

Run it as-is. You're within spec, technically. It'll probably last for years and years if you don't beat on it too terribly hard. These are tough motors.

Just my 2-cents

Cheers
DD
 
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Old 01-18-2009, 08:59 PM
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Default RE: Bypass Valve for oil may be clogged

Oh Doug, your 2 cents are priceless. I can't afford any huge turmoil and my wife would hang me if it were necessary. I will continue to drive like a Grandpa, and change the oil religously. Should I squirt in a little of a higher weight oil to increase pressure, or just stick with the Castrol 20W-50?
 
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Old 01-18-2009, 09:04 PM
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Default RE: Bypass Valve for oil may be clogged

The 20/50 is fine.

Enjoy the car

Cheers
DD
 
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Old 09-29-2011, 01:53 PM
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Wow this is exactly what I have just noticed. A few miles before my oil change was due, my pressure level dropped to 1 or 2 and then the oil light would come on. Now after the oil change i still show very low oil pressure and the light come on randomly Oh no
 
 
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