86 XJ6 Series III - Water in intake manifold

(Adam Thompson) #1

Hello, my XJ6 quit running. My investigation of the problem led me to water in the intake manifold (pictures attached). I’m guessing this means a blown head gasket but I thought I should post before assuming I know what the issue is.

(Carl Hutchins, Jr. ) #2

Perhaps not so drastic.

I’m not sure how this is accomplished on the XK engine, but the mixture is cooled and or heated by water from the cooling system.

Crack or corrosion??


(Robin O'Connor) #3

Get a TeeKay test performed before making too many assumptions.

(David Jauch) #4

Gross. Carl is right that the throttle is heated by coolant to prevent icing but a crack seems far fetched.
When you check out the breather it‘ll be full of the same mayonnaise and while a small amount is more or less normal you have a lot of coolant. Not only that, but for the water to take this route it must evaporate from the crankcase and condense in the intake!
A second (or third) possibility is that the intake manifold gasket has given up. The intake tract has air and coolant passages next to each other, and if water leaks in there it might both trickle down into the plenum AND the cylinder, giving you both the mayonnaise (via the water that ran down the cylinder into the oil), and a lot of water in the intake manifold.

Before you pull the head you might want to look at the intake manifold gasket. With a small bottle jack and a few dollars for the gasket you‘ll take a few hours, and if it seems to be the head gasket after all you didn’t lose anything.

This is what that looks like:

I hope it didn’t hydrolock when it quit?


(Adam Thompson) #5

I did a compression test, and I’m only getting 90 psi in the #4 cylinder and 30 psi in the #5. I assume the results of the compression test would confirm a blown head gasket.

So here’s the next question, I have an 83 xjs parts car with an engine in it that I believe is good. If I get the engine running and it seems to run well, would it be easier to swap engines or do a head gasket repair? I’ve swapped engines before but never changed a head gasket so that would be a little intimidating to me.



(phillip keeter) #6

Check for water in the fuel supply. Looks like a lot of water in the intake but you never say never with these crazy cars.

(Robin O'Connor) #7

Isn’t this a V12? A bit different to the XK engine in the S111

(Paul M. Novak) #8

Your 1986 XJ6 has a 4.2L I6 XK engine in it and your 1983 XJ-S has a 5.3L V12 in it. Some listers, like Doug Dwyer, have converted an XJ6 to an XJ12 but I believe that the technical challenges to do that are not trivial even if you have all the necessary parts on hand. I have removed and replaced several 4.2L.cylinder heads, and removed and replaced two failed 4.2L XK engines and I suspect that the challenges of swapping out a 4.2L engine for a 5.3L V12 are much greater than removing and replacing a cylinder head. Given the choice I would definitely opt for the cylinder head removal (assuming that it was necessary) and replacement long before I would consider the engine change.


(Frank Andersen) #9

Spot on, Adam - when you find coolant where it should not be…

You raise an interesting question choosing between an engine swap and a head gasket change - like for like engines…:slight_smile:

If you have a perfectly good replacement engine - a swap is hard work, but with no surprises. Removing the head for whatever reason, you may encounter all sorts of interesting things - time and money consuming…

I’m joking, of course - tackle the head gasket change; it is logical choice, intimidating or not…

xj6 85 Sov Europe (UK/NZ)

(David Jauch) #10

Yes, the compression test would indicate a head gasket failure. I think you‘ll be best off changing the gasket on your existing engine.

(Paul M. Novak) #11

In one of his emails Adam said he was considering an engine swap with an engine from a “83 xjs”. I have done two 4.2L to 4.2L XJ6 engine swaps, but I have never put a 5.3L V12 into 4.2L car and suspect that there would be lots of challenges with doing that. I know that others (like Doug Dwyer ) have done it. But the work required has got to be a lot more (10 times?) what a cylinder removal and replacement is.

I suppose that it could have been a typo in Adam’s post and he meant to say “83 xj6” instead of “83 xjs”. I think we will have to hear back for Adam on this.


(Adam Thompson) #12

Sorry everyone for the confusion. I meant to say engine swap for the 83 xj6. The swap would be a like for like.

(Adam Thompson) #13

@Paul_M_Novak2 - I replaced a few small block ford/chevy engines and they were only moderately painful. How painful would you say the xj6 4.2 swap is?


(Paul M. Novak) #14

I have been posting my progress on Jag-Lovers regularly since December in a thread called “Engine Transplant 1984 XJ6 Vanden Plas”. This was the second time I have removed a failing 4.2L XK engine in one of my XJ6s and replaced it with a nicely running engine from a XJ6 parts car that I purchased. If you haven’t seen my posts you should review them to get an idea of what I did. I also included a lot of pictures. My 1984 XJ6 Vanden Plas is running nicely now with its replacement engine but I still have some more reassembly to do and interior restoration.
I am restoring this car to like new concours condition so some of the work that I did will not be applicable to you. But, for me as a hobbyist, the two engine swaps were the most challenging technical work that I have ever done and so I would rate them a 10 out of 10. I have also done several XK engine cylinder head removal and replacements and would rate them about a 3 or 4 out of 10 in complexity. There are still a lot of challenges in getting it right, but not as much removal and replacement and not as many chances for things to go wrong.


(Carl Hutchins, Jr. ) #15

Hmm ??

  1. Compression low in only one cylinder? Often, it is low in two adjacent bores. A “thin” area ion the gasket surfaces ! Low for other reasons, not related to gasket failure?

  2. I may well be missing something. I don’t see a gasket t failure as a reason for water in the intake???

  3. SBC’s and SBF’s and transmissions are much lighter and far less bulky. And, I sense a lot less ancillary equipment to deal with .

But, the concept is the same… Plan carefully. Proceed carefully.


(David Jauch) #16

He mentioned two adjacent bores. It sure is a lot of water so if it ran fine it can still be my intake manifold gasket; however not with that compression test.

By the way, if I had a spare engine I would still be more afraid of R&R than ‚just‘ the head.

(Aristides Balanos) #17

I guess it’s a question of how deep one wants to dive into…
Changing the head gasket is already deep, as once you take the head off wouldn’t you want to recondition it?
Wouldn’t you change your water pump etc etc…?

Then if you swap engines just the in and out is a pretty huge job by it’s self.
Then, are you sure that the replacement engine is in such a good nick and worth of all that effort?
That it hasn’t overheated, starved of oil, dropped valve seats etc etc?
In my opinion such an endeavor is really worth the while if done like Paul Novak did it, you put in a fully reconditioned engine, and I wouldn’t do it any other way.


(Carl Hutchins, Jr. ) #18

Reminds me of a couple of my ancient critters of old.

  1. EC, the younger brother of a school chum was a bit nuts. he thought it great sport to press the starter button an a 'raggedy" 34 Ford coupe. In spite of much abuse, the car ran well. Older brother did a swap with a local amateur car butcher. Toothless engine for a “toothed” one. It craned and ran. alas, cracked block, Oil became soup. It lubed that way??? I swapped a pistol for it. As I worked in a full service station, used oil was in plentiful supply. At times, real good stuff.
    thousand mile changes from cream puff cars !!

  2. I and a workmate rebuilt the engine in my 37 Ford. several errors. But, it ran great, for a while!!! Busted the crank at the center main!!! As a student, I had no more money to do it again. But, school chum, Roy was fixing the hand me down 39 Ford. Including a swapped rebuild for the Mercury engine that ran great but ate oil!! We found a crank and put it in. it went to the dealer as the core. I cleaned up the Mercury and installed it in my 37. OK!! Same solution. good oil, cheap.
    Sold off to some guys that made a “jalopy racer” of it. I got to see it win the “main” at a local track !!! ,

Engine swaps done with a chain fall hung from a beam in my folk’s garage.


(Robert and Darlene Stevenson) #19

Carl Hutchins, Jr.

    May 14

Carl, I’m sure that you can appreciate this.We pulled the engine from my 39 Ford coupe with a chain fall hung on a fan belt wrapped around the upper pipe on swings at a local school on a Sunday evening.

Engine swaps done with a chain fall hung from a beam in my folk’s garage.


Visit Topic or reply to this email to respond.

You are receiving this because you enabled mailing list mode.

To unsubscribe from these emails, click here.