My 06 Jag Super V8 has a head gasket leak, verified by combustion gasses in the coolant, causing excess pressure in the cooling system. After watching videos of the complicated head gasket replacement on You Tube, I decided to take the advice of our local independent Jag mechanic and try K-seal first. I found a K-seal product it calls Ultimate Head Gasket Repair, and added a bottle to the cooling system which did stop a radiator leak that had developed. K-Seal recommends removing the spark plugs from the cylinder or cylinders are leaking and doing several warm ups from cold to allow the product to “work its magic” without outward pressure from combustion.

I have performed dry and wet compression tests that did not immediately identify which cylinders might be leaking, so I am asking advice on anything else I might do to identify them.

Dry Compression test: Elevation 1400 feet, temperature 77 degrees F

All spark plugs out, engine cold, throttle closed, the engine cranked for 7 revolutions (twice for each cylinder to make sure I had the gage hose screwed in tight). I list the highest or average reading for each cylinder.

Left Bank Right Bank

#2 115 #1 130

#4 120 #3 125

#6 128 #5 128

#8 125 #7 120

Wet Compression test: Elevation 1400 feet, temperature 80 degrees F

All spark plugs out, engine cold, throttle open, the engine cranked for 7-8 revolutions

(For the wet compression test I used a small pump oil can with a plastic hose on it to pump 1/2 Oz of 2 cycle oil (7 pump strokes) into each cylinder, one at a time, and cranked the engine 8 compression strokes with the accelerator pressed. Readings might have been slightly higher on some cylinders (5 PSI?) due to some leak down in the time it took me to exit the car and read the compression gage.)

Left Bank Right Bank

#2 185 #1 175

#4 180 #3 175-180

#6 175-180 #5 185

#8 175 #7 175

Then about two hours later without adding any more oil I checked compression again with my wife cranking the engine 7-8 revolutions with the accelerator pressed and me watching the compression gage.

Left Bank Right Bank

#2 170 #1 170

#4 170 #3 170

#6 170 #5 170

#8 160 #7 165

I do not have a leak-down tester, but did observe a slow leak down from maximum pressure on my gage for most if not all cylinders, but I don’t know it is was within the cylinders or possibly the gage itself.

Any advice on further tests I might perform would be appreciated

 

- "Headgasket in a Can" stuff is sketchy, to say the very least (unless your fixing a Model A). Problem is that a combustion leak has about 300 times more pressure behind it than a radiator leak. And, the stuff makes a real mess of your cooling system (eg, your heater core, aux pumps, rad core etc). I pity the mechanic who has to deal with the aftermath...

- Compression test generally won't show a head gasket seeping combustion gas into a coolant passage (see above). Ditto leakdown. Combustion gas (HC) in coolant is the marker

- Your car v probably has been overheated at some point

 

K-Seal is very useful for cracked blocks/heads but a little less effective on actual head gaskets. In my experience it won’t clog much especially with how small the containers are.

Just toss the sealer in and get ready to do the full hg repair or source a replacement engine.

 

I think that you would find it better all the way around to simply scout around for another engine. My second piece of advice is to have your mechanic swap the engines.

 

Snake oil is still being sold, buyer beware.
Do believe Rickk has given you some good advise.
A bitter pill to swallow, but i believe it might be your best bet.

 

+1 on the above.

 

Hi Phil,

I'm sorry to hear of your trouble.

Head gasket replacement isn't particularly difficult, it's just time consuming, so the labor costs can be high. Also, there are plenty of non-related parts to consider replacing preemptively as part of the process. But the same holds true with a salvaged engine: before you install it you should consider replacing things like the oil pan gasket, valley and other difficult-to-access coolant hoses, supercharger gaskets, intake manifold gaskets, cam cover gaskets, etc. Anything that is more difficult to replace with the engine in situ.

So my advice would be to put together detailed estimates for both approaches and then make your decision. My suspicion is that if the K-Seal has helped restore your compression, your heads are probably not badly warped, so replacing the head gaskets might be a perfectly acceptable and successful approach.

The one issue I can think of that would make me immediately shop for a good salvaged engine would be if you are hearing any knocking sounds from your engine that could suggest problems with connecting rod bearings, which is what happened to my XJR.

Cheers,

Don

 

Thanks to all for the replies. Apparently compression testing is not going to reveal which cylinder(s) are pressurizing the coolant if it only happens under combustion.

To Don, I can't say that K-seal restored compression because I had not tested compression before; it did stop a radiator leak that had developed while the SV8 was idle. There are no other issues with the engine that I am aware of and no extraneous noises. I have had a series of coolant leaks and have replaced most of the hoses, the water pump, thermostats, and the brushes in the auxiliary pump. I did have an overheat incident when the top radiator hose backed off and it lost coolant out in the sticks and I added a gallon I carried with me and had to find a town with an auto supply to top it up. I'm not sure if the hose backing off was a cause or a result of excess pressure. If I pressure test the cooling system cold now, it will hold 20 PSI for hours and I find no coolant in the oil or oil in the coolant. It seems to run fine except for the excess cooling system pressure.

I guess I'll put the spark plugs back in and try a few more warm-up cycles and then test for combustion gasses again. I had purchased the timing tools in case I decided to attempt the head gasket change myself, but from the videos I saw, a lift is almost essential to the process. Last I checked the gasket set was around $450. I have plenty of time in this pandemic era, and the hand tools, but at the age of 78 I am not certain I have the stamina for the project.

 

Phil,
I've been following your thread to see how you make out. I looked up the "K Seal" stuff on Amazon and read some of the feedback. Dang, some folks have had success with it. So, please do reassemble and test drive. Let us know how it goes. If the gasket leakage is a minor seep, maybe it will seal up. Absolutely no harm in trying, at this point. I'm rooting for you...

Regarding head gaskets, I haven't done the job on an SC 4.2L (or any other car, in years). If my '07 XJR (130K miles) were to have the same problem, though, I would probably tackle it (though I'm in my 60's now). Just because I like the car. (I'm about to do the Valley Hose, water pump, etc, and that's about half way there).

My (dated and limited) experience with head gasket problems is that they tend to be the result of an overheating event. Symptoms such as burping out overflow coolant are typical. As things get worse, overheating, contaminated oil, split expansion tanks, white exhaust smoke (esp on start up), and even hydro lock are possible. Its when you get into these final throes that even a compression test could begin to isolate the cylinder (but by this time the engine may be toast; ethylene glycol damages about everything it gets into)

Years ago, during my play racing days, friend with an Alfa Spider track car had just had his engine rebuilt (2.0L DOHC Four; wet liners). First event of the season, and creamy oil. Rather than pull the engine (again...), we put in a can of Bars Leaks, and darned if that didn't seal it for the rest of the season. The rebuild guy went through it again over the next winter, found nothing wrong, and instructed use of Bars Leak with all his Alfa rebuilds going forward. Belt and suspenders, I guess, and track cars don't have heaters, etc.

As a kid, I worked for about a year at a San Diego Chevrolet/GMC dealership; line mechanic, then service writer. GM had begun delivering new cars and trucks with "Cooling System Conditioner" (read: Radiator Sealer, made by Prestone, IRRC). This practice had begun with the infamous Vega, which often had head gaskets leaking coolant down the side of the block right as they came off the GM transporter. The fix became this sealer, which generally worked long enough to get the cars off the lot, some with multiple bottles of this goop in them.
Well, leaving the Vega aside, sealer became The Modern Warranty Work Deal for dripping hoses, etc. Paid 15 minutes warranty flat rate. We used it in everything, adding to the stuff GM already put in. And, come January (about the only time you need a heater in San Diego), the dealership was swamped with "No Heat" warranty work. Mostly seized up heater control valves, but also lots of plugged up heater cores and damaged heater control assemblies (some of the latter requiring dash pulls). Next Spring, a spate of overheating; plugged thermostats, plugged radiators (and, blown head gaskets, seized engines, as in "...was just trying to make it home, son"). So much for radiator sealer...

 

Because of old stories of Jaguar dealers adding Bars Leaks to new cars as a Prophylactic remedy for future leaks and than finding inches of sludge in the radiator bottom tanks, I was hesitant to try head gasket sealer in my SV8, but perhaps the products have improved since then. I did consider Blue Devil head gasket sealer, but eventually decided to try the K-seal head gasket repair because it was stated to mix with Dex-Cool and did not require flushing of the system, removing the thermostats, and adding it with plain water to do its work. I have driven the car around my out-in-the-boondocks neighborhood a few times to get it to full operating temperature since adding the K-seal, but have not done a combustion gas test because I was hoping to find a leaking cylinder and do the warm-up with spark plug out that K-seal recommends. Guess I'll button it up and take a few more drives and then try the combustion gas test again.

Related question: Does holding the accelerator to the floor while cranking the starter on our drive-by-wire cars actually open the throttle? I know most sources recommend a wide open throttle for compression tests, but didn't know if putting "pedal to the metal" actually opened the throttle on our cars.

 

"Does holding the accelerator to the floor while cranking the starter on our drive-by-wire cars actually open the throttle? "

Great question! Believe the answer is yes.
Regarding compression testing:
- Feel free to let the engine spin (throttle open) until gauge reading maxes out
- Your numbers are OK for a cold engine and limited cranking (more accurate and generally more even between cylinders with warm engine and extended cranking)
- The SC engines are lower compression (9.0:1) vs NA (11.0:1), I believe
- Adding oil will (in my experience) always raise gauge readings in a normal engine (the oil test may confirm leaking valve(s) if compression doesn't rise as significantly as the rest on a leaking valve cylinder)

I'll button it up and take a few more drives and then try the combustion gas test again

- How are you testing coolant for combustion gas?
- Beware that chemical test (eg, if dye in test cylinder turns yellow...) may give you a false positive with coolant that's been contaminated by bad head gasket (ask me how I know this)
- Maybe drive your car normally for a few weeks. If it stops burping coolant and seems OK (fingers crossed), have an emissions shop wave an HC wand over the expansion tank. If nothing or faint, I would change coolant in yet another month or so (rinse system with fresh water; heater on thermo open, then fresh coolant) and proceed to carefully bow three times to the jag gods (for luck)

 

I checked the compression on #2 today with my wife cranking the engine, first with no throttle, then WOT, and then again with no throttle. The result was no T 132 PSI ,WOT 135 PSI, and no T again 132 PSI, so the throttle apparently does open and it does make a small difference.

I did use a chemical testing kit to test for combustion gasses when I was seeing coolant blown back from the pressure cap. So the gasses do not dissipate over time?

I put the plugs in today just before a storm came through so I'll try to finish up with the coils tomorrow.

 

I did use a chemical testing kit to test for combustion gasses when I was seeing coolant blown back from the pressure cap. So the gasses do not dissipate over time?

- The contaminated coolant may dissipate HC gases over time (I'm not quite sure), but will give a false positive if you chemical test shortly after correcting the combustion gas intrusion
- Suggest some gentle drive cycles (to minimize combustion pressure), allowing that K Seal stuff to work. Not sure of the chemistry, but assume the stuff precipitates some type of "sealer" in the presence of combustion gas (or atmosphere). If so, best to let it layer up a bit before tipping into SC boost too much
- Suggest try this for a few drives, and see if the coolant burping subsides. If and when all seems well, you can think about HC testing again (ref my previous post)

(Have a great weekend)

 

One thing to be cautious of is that while you are squeezing the bulb to draw fumes through the test fluid, if any wet coolant gets inhaled into the test tube it will turn the fluid yellow and create a false positive. I think I recall that the instructions for the kit I have (made by Balkamp and purchased from NAPA) state that the coolant level must be at least 2 inches below the end of the rubber tip of the test tube, and if the coolant level is too high, some should be suctioned or drained out to lower the level sufficiently before conducting the test.

 

I just want to chime in as it relates to the fixes in a bottle. I would highly advise not to put anything in your car that the manufacturer does not recommend. Coming from the Cadillac Northstar community we have seen it done several times and each time (assuming the person reports back) is a head gasket failure. Sometimes a month out sometimes a year out. But it still happens. Then in addition to having to replace the HG anyway you now have a bunch of gunk in your cooling system that needs to be cleared out. Especially on the SC version there is more than just a couple of coolant lines and a radiator to clean.