After experiencing hesitation/misfire & stall after warm up I’ve cleaned the vee, coils, plugs, flywheel sensor, CTS.Today I put new gas in the car and after I started it I saw no change (with new flyweel sensor). But what I did get was a sound like a wrench in the cylinder. I shut the car off and left it for 30 minutes I restarted it twice. Once I heard nothing in 2 minutes. 2nd time I head the nose again. This is not a tappet noise. It’s loud. It’s intermittent.
I spotted an intake gasket leak at B6 (validated with starter fluid) and consequently loss of vacuum. I was already planning a compression test.
I’d like some input on sequence of work. I planned on removing the left bank intake manifold. I believe that’s the side the noise came from but I did not run the car long enough to isolate.
I’m aware there are lots of posts on the subject and will be reading them over the next few days.
This car has 53k miles on the motor. I’ve owned it since 43k. I believe I’m paying the price for not driving it enough. It has run warm but not overheated since I’ve owned it.
Gary
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
The easy way to remove the intakes is the whole kit 'n kaboodle, both intake manifolds and the injectors, all at once.
Kirbert - Can I do a compression test with both intake manifolds off? I was planning on taking the fuel rail and injectors off to send them off for cleaning and building a pressure test rig. With the leak at B6 how can I determine where the noise is coming from before I tear down? If I can do I then do a compression then leak test? I’m concerned about piston damage.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
4
Can’t say anyone’s ever asked that before. Offhand I dunno why not, although you’d obviously need to be very careful not to suck anything into the engine while you’re at it.
You might want to invest the $10 or so in one of those borescope cameras for a smartphone. You could stick it into a spark plug hole and have a look around inside.
I would suggest resolving the engine noise is initially more important than fixing a manifold gasket. And a leak down test, properly conducted, will give you more data than a compression test. You can perform a leak down test with a non-started engine by turning over the engine at the front end with a wrench. Less likely damage to engine parts. The noise being intermittent is odd. I have heard three occasions of a dropped valve seat and all three the tapping was always there…not intermittent. Rising/falling in sequence with engine rpm. And you did not mention an overheating episode. SD Faircloth
Many years ago I did a big ‘clean the vee’ job on my XJS. All the usual stuff.
On start-up there was a hellacious clattering. I stopped the engine immediately, of course. I spent hours and hours of looking for the source of the noise.
Finding nothing, I held my breath and started the engine again.
Purred like a kitten. Never did figure out what the noise was.
With an abundance of caution, I would not run, or crank the engine, till a leakdown test has been done. To get the tested piston in the correct position for that, I’d turn the engine over by hand.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
8
I’m trying to remember if an intake manifold leak is a known cause of a dropped valve seat. I seem to recall it causing some sort of engine damage.
No question the manifold gasket is minor and less important. Good info on doing test without startiing the engine. Intermittent is odd. It ran, started to warm up & let out the “clank”. First time I thought I’d left a wrench and hit got tangled up with the belts, although I’m sure it was at the back. Re overheating - One time I ran hot 7k miles ago. I found a leak in the left bank hose. That was before I understood the left bank cooling challenge. In hindsight I’'m wondering whether this is now …although some years later, the result of that.
Yes I would think that was the cause of the poor run after warmup. What puzzles me is if the gasket was not put in correctly by the PO why would it suddenly cause the weak running now. Also it makes me wonder if/why the B bank gasket was replaced (If it was). Image of rear of B6 showing gasket out of place. I have not checked the manifold studs yet to see if they are l loose. I’ll do that tomorrow. Anyone know the torque values off hand?
Its as though this has suddenly come on after along period of not running the car.
Thanks for the link. I’ve been checking them out this morning. Seems like Depstech & Rotek are the most visible in searches. Biggest issue seems to be crappy Chinese software. Might get a wi-fi one to avoid tethering the phone. Depstech sells an optional attachment kit with different mirror angles for $17 but it only fits the 8mm size models. Suspect the 90 deg std mirror angle would work but who knows. For this purpose I would think 5mm or 8mm would work. Shortest focal length I’ve seen is on a Nidage (1.18"-3.94"). 5mm ones may be better for small passageways. Nidage No reviews unfortunately.
One with too long a focal length won’t focus closeup. I’ll pick one and order it today. Likely I’ll remove the intake manifold and camshaft cover so I can take a good all around look.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
17
My brother bought one with a “feature” that the flexible scope was less flexible than most. Apparently them flopping around is an issue, having one a bit stiffer can be good.
Went with this one because of the focal length 1.2" to 15.7" and the overall reviews. 2MP might be better than the 1MP on the 5.5mm version and the zoom on that one seemed to be useless per reviewers. Very easy to get analysis paralysis on these things. Reviews seem to indicate this brand is stiff when bent. Depstech 2MP Wi-Fi Borescope
Well…the scope works well but unfortunately I cannot see the valves even with the mirror attachment. The cable is too stiff to bend 180 deg. So I’m looking for another scope. I’ll post images later. With a cheap scope I think you have to do something like this on the V12 and the wire has to be very flexible. DIY Scope Hack
In the meantime I’m reading and prepping to remove the intake manifold and camshaft cover to see what I’m dealing with and that I have parts etc on hand. I’ve looked at Bernard’s and Ed’s write ups and I’ll read the section in THE BOOK tonight. The '92 of course has some slight differences to earlier models.
One thing I’d like input on. Looking at parts I noticed that the intake manifold gasket - C43354 - is still shown as an individual cylinder gasket and is sold that way by SNG and others. I know there are aftermarket ones and I’ve read threads on gore-tex etc. My question is this - My gasket is a continuous one on both manifolds. I’ve attached images of the area at B6 where the leak is and also between B3 and B4. The entire gasket is continuous. Can anyone confirm that the car came like this or does it suggest the manifolds have been off before?
