I have a 2002 XJ 4.0 N/A Vanden Plas. It has what I expect to be a broken valve spring on an intake valve. There is zero compression on #8 while the other 7 are about 200 psi within the normal ranges of difference. I put the cylinder in compression stroke position and shot compressed air into it. The air blew out the throttle body leading me to believe one of the intake valves it stuck open. There is no water in the oil or visa versa to suggest a head gasket issue and #7 has 220 psi so I hae to assume it's an intake valve. I have rebuilt many engines in my days but they were all GM or Ford. Never an overhead cam or dual as in this case. Am I able to remove the spring without removing the head? I have done it before in GM V8s by filling the cylinder with compressed air to keep the vale from dropping. Once I remove the broken spring (if that's the case) it would seal. Could someone please offer me some insight as to whether I can replace the spring without removing the head?

 

Pull the valve cover off first and inspect. May have a bent valve or dropped valve seat from overheating??
If the spring looks ok, you could pull the intake manifold to verify if the valve seat dropped down. But first, you need answers. Inspect.

 

I agree with addicted to boost you need to pull the valve cover. Bent valves or a valve seat and drop down that’s what I seem to run into it be nice if it was a simple as a bad spring good luck

 

almost certain the seat dropped. they probably kept driving it till it hit overheat shut down point

 

I've done this on a 2003 ford f250 5.4l motor.
if it is just a broken sping.
I took a 3/8 piece of cotton rope and coiled in to the cylinder, Hand crank the engine to bring the piston down 1st once you have about 2 ft of the rope in slowly Hand Crank the engine to get the piston to compress the Rope against the Valve .. Now you should be good to remove the keys and replace the Valve Spring its also a good time to replace the Valve seal while your there .
All This Worked for me because it was just a Broken Spring.

good luck.
jay

 

How do you see the valves with the valve cover off? All you see are the spark plug holes and 2 cams.

 

I have replaced valve springs and seals a number of times on North American V8s but it's trying to examine for damage without removing the head. It's double overhead cam and the springs are under the cams. It's a completely different design.

 

Hi
Your not going to see the valve face itself just the stem under the valve spring , if your worried about the Valve or Valve Seat you can try some compressed air just need to hold/pull the valve stem up while Appling some air pressure.
1st.Crank the engine by hand until the cam rocker is at it highest point.
I didn't check where you live but it's pretty cheap and easy to get what you need from say Harbor Freight.

 

No she pulled over when the warning light went off and had it towed home. She went on vacation for a couple weeks and when she started the car upon returning it was running rough and drove it to the repair shop where they ripped her off for a few grand for coil and plugs. Then when it was still doing the same thing they quoted her another 3 grand for a new head gasket. At that point she had enough and i got it for 2 grand. It's in otherwise mint condition with 80 thousand miles and documentation to the original sale.

 

I believe I posted a few pictures here of my engine when the guys here were helping me with my timing chain replacement.
I'll have to look. But I'm pretty sure the rope trick for just replacing a valve spring.
I have a 2001 vdp 4.0L


tackling some Rust

 

So you are saying I must remove the cam as well as he valve cover because how do I see the valve stem and spring otherwise? I know about compressed air as I put in my post doing so. With the cylinder on compression stroke I had the air coming out the throttle body. My inquiry was how far do i have to go to access the spring and stem. I have done numerous chevy or fords but this is my first Jag. I'm unable to see how I can do anything without removing the timing cover to remove the cam which first requires me to purchase that Jaguar balancer tool and timing gear tool. I'm in Canada just outside Vancouver. can't access Harbor Freight because the US isn't allowing vaccinated Canadians across the border, just Europeans and other countries. Nice neighbors. Or neighbours in Canadian English.

 

I bought this car as a project car.
Ran like Ship, Smoked badly, must had 15 + DTC, codes.
someone attempted to replace a timing chain tensioner after it completely exploded it was a mess. And a short on a knock senor wire that was giving me all the fault codes and keep it in safe mode. But with help from the guys here she's running nicely.

 

Inspect is what I'm doing. What I was trying to find out is how far do I have to go in removal to inspect the valve springs and stems? Valve covers only show cams and and spark plug holes. It appears it's remove the timing chains and cams which means I might as well just get prepared to remove the head. That means purchase the specialty tools needed for a Jag. I've only worked on NA V8s and removing valve covers does give you the view of stems and springs. I was trying to find out how far I have to go to get that view before I start taking things apart and making the car not driveable.

 

Have you have some one crank the engine with valve cover off?might see your problem if stuck valve...it won’t be going up and down. have all plug wires off ..so no start..compression test ?

 

Mine is an otherwise mint condition 2002 Vanden Plas. It's blowing compressed air out of the throttle body through #8 on the compression stroke. The rest of the engine is fine. Just trying to discover how far I have to tear it down to get the answer. I am unsure yet if I want to do it myself or drive it to a Jag shop to repair once I know what the problem is. I only paid 2,000 so I have room to spend within the value of the car which I put at 10,000 CND.

 

Yes as I noted in the original post I got around 200 to 225 from 1 to 7 but #8 is zero. It's my 1st DOHC engine so I'm not familiar with the valve train. I was trying to discover how far I have to tear it down to discover the problem. Compressed air is coming through the throttle body on the compression stroke in #8 which is why I suspect one of the intake valves. It runs and was hoping to know the cause before I decide t fix it myself or send it to a Jag shop and take out a second mortgage to pay the bill.

 

This is one broke a timing chain

 

Ok your Right big difference in engine. You can not see the spring like on a Ford 5.4 l...
Right now I would start with a compression test just to find out if the valve is closing/holding compression. If that doesn't work
Try hand cranking until the lobes are up and pumping some compressed air into the cylinder
That's all I can think of before removing the whole cam off that side.

 

K”

The valve

X308

X308

 

Ok if that's it with the cam removed .
I would would do the rope thingy remove the cap over the valve spring compress the spring with a O2senor socket and fish the keepers out with a small magnet.
I would use a small piece small metal across those 2 holes that hold the cam down. Shouldn't take much pressure.
That's my thinking.
And again That If This is just to replace a Broken Spring.