I recently bought a '95 XJR and have been sorting out some minor issues. I have the original crankcase ventilation hose with the car, currently there is only a small filter on the cam cover, which works but it's a bit smelly when driving.

The hose has 3 ends - one attaches to the cam cover, the second attaches to the intake plenum near the firewall, but where does the third end attach? I can see a blocked off port in the airbox under the airfilter, is this where this end is supposed to go?

I have studied the factory manual, parts manuals and various forum posts but can't work it out.

Cheers!

 

In the XJS, the third end went back to the oil pan. I'm not around my car for the rest of the week, but when I get there, I can show you that its there so any oil sucked in through the camcover, would fall back into the oil sump.

Doesn't work well if you've ever taken out your throttle body. Jaguar updated it with a little plastic egg looking part that was supposed to help filter out air from oil. That didn't work much better either.

 

Hmm interesting... i can't recall seeing anything plugged on the block, and the dipstick tube doesn't have any attachment for a hose either, i assumed there was some sort of positive crankcase pressure system removed. It appears the third end of the hose goes down under the intake plenum but from there... no idea!

Cheers
Mike

 

The smaller hose connects to the top of the bypass valve body, between the throttle body and supercharger inlet.

See this thread:

https://www.jaguarforums.com/forum/x...essary-180030/


If you don't currently have a catastrophic vacuum leak, the nipple on top of the bypass valve body must be capped.

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Excellent thanks for that... is this the hose circled in the attached pdf? In front of the throttle body before the SC?

I hope i can get under there without removing the intercooler!

Cheers

 

OK scratch that... what i posted before is a coolant hose... i just remembered i took some photos when i cleaned the throttle body...

Can anyone tell me where exactly it attaches to the throttle body?

 

Correct, the red circled hose is where the smaller of the breather hoses attaches. If you don't mind, I'm going to "steal" that PDF and put it in the thread where I ask about that hose as well, as it is the best illustration I've seen of where that hose attaches



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There are two coolant hoses that attach to the throttle body, one supplies heated water, the second returns the heated water to the coolant circuit.

Both hoses attach to two identical brass nipples/barbs on the bottom of the throttle body, 180 degrees opposite each other, transverse to the throttle body throat. If you look at the bottom of the throttle body, you really can't miss them.

They just pass heated water through the the base of the throttle body, so it really doesn't matter which hose attaches to which nipple/barb, however the long hose you show in the photo above that is currently attached to the bypass valve body (where the small breather vacuum hose should be attached) is normally attached to the throttle body nipple/barb closest to the engine block. The return line branches off the coolant lines that run along the inner fender and attaches to the other nipple/barb.

Hope that helps!

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Ok now i'm confused... that nipple has a coolant line attached? It has never been removed before and the car runs fine, surely a coolant hose connected to a throttle body air inlet would spell disaster?... Or is there another nipple that i cannot see in the photos?

I have attached a couple more so you can see where the hose goes...

The two small nipples under the throttle body were plugged long ago and not in use.

Could you clarify further? Thanks again!

 

Yep, your photos are very clear, a coolant line is erroneously connected to the SC bypass valve body where the smaller crankcase breather line should be connected. That is very wrong.

Although not a lot more helpful, see the following diagram where you can see that the bypass valve body is hollow and the nipple/hose on top just opens into the body and not for coolant passages.

https://www.jaguarclassicparts.com/u...e-supercharged

I also know this is true as I sprayed a lot of carb cleaner into that nipple and up through it to clean out oil, and of course pulled the smaller breather hose off of it. The PDF image you first posted with the red circle is showing the correctly attached smaller breather hose. And you'll also notice that small breather hose does not use a clamp of any kind, since it is vacuum.

As you point out, connecting one of the coolant hoses should have created a certainly catastrophic scenario when running where coolant from the intercooler would have been sucked into the intake tract following the TB and prior to the SC. Did the car ever run with that hose connected there? It sounds like you have said it did. That is so weird. Did you lose a lot of coolant when running? Maybe is somehow only sucked in a little bit of coolant, effectively giving you "water injection" by accident, but I don't see how it couldn't just suck huge amounts of water.

That hose should be going to one of the coolant nipples/barbs on the bottom of the TB, that you note are plugged on yours. And there is another coolant hose that branches off from a hose by the fender that attaches to the other plugged nipple/barb. Those form the in/out circuit through the TB. Where is that unused hose on your car? Is it plugged?

Bottom line, yours is plumbed incorrectly. Coolant does not connect to the top of the TB and should in a worst case introduce large amounts of water into your engine.


BTW, I also see that you are missing the connection of another vacuum line right below the vacuum line that coils over the bypass valve body to actuate the SC bypass valve. See the bare "gold" nipple/barb? That nipple/barb should have a vacuum line attached that runs back toward the firewall. I'm not sure what that vacuum line supplies off-hand, but perhaps cruise-control. If you just took it off, no worries, but I saw it was missing and thought I'd call it out. With no vacuum line attached, you'll have a heck of a vacuum leak and unmetered air entry.


BTW BTW... I see someone took the shortcut I ALMOST took with the forward knock sensor wiring, which was to cut it off and repair it with DIY connectors because it seemed so impossible to reach to disconnect without removing the coolant pipe and maybe SC. My son and I too faced this final connection dilemma. But it turned out that the Jaguar engineers weren't as daft as we thought. Where all the other connectors required depression of the wire clip to pull it off, that one and only forward knock sensor connector doesn't require that effort. The connector is similarly constructed as the others, except it's spring clip is already depressed and is just held on by the spring snapping on. So a quick tug pulls it right off, and an easy push and "snap" and its back on. We had struggled with that last connector for a good hour trying to depress the spring clip/wire with a long screwdriver with no effect (because it didn't depress, by design!!) only to then discover a strong tug pulled it right off. We were both so happy and frustrated! Ha.


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That is truly bizarre, i never touched that coolant hose when i cleaned the t/b as i assumed it was supposed to be there and had no reason to disconnect it.

The even more bizarre thing is that there is no evidence of 'water injection', as it doesn't use any coolant... and i just replaced the oil, no evidence of water contamination in the oil.

Crazy.... sounds like i might be pulling the intake off again... nightmare. And yes, the knock sensor wiring was already modified.

And yes, the unused barb was a vac line for something else that was replaced when it was put back together.

 

Went and double-checked the photos I took when I disassembled my intake tract, and yep the smaller breather hose attaches to the top of the TB, not one of the coolant hoses.

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Good stuff, appreciate that. I hope i can sneak under there with a 7mm spanner to undue the hose clamp without taking off the intercooler/manifold... wish me luck!