I had a coolant leak which caused my 06 SV8 to lose coolant and get hot several times before I replaced the water pump and thermostat and repaired the two electric coolant pumps. Then it was OK for 3600 miles, but about 3000 miles ago on a trip, the top radiator hose backed off and it lost a couple of gallons of coolant and the Temp got up to 230F before I could stop and replace the hose and find an auto store to replace the Dex-Cool coolant. After that it developed another leak at a plastic quick connect fitting to a heater pipe which I replaced along with the top radiator hose assembly. Since then the new top radiator hose with a new spring clamp backed off twice (so I put two jubilee hose clamps on it) and now it loses about a cup of coolant from under the new 140 Kpa pressure cap per 100 miles due to high coolant system pressure, and it has residual pressure in the system even after parked for a week. A block test indicated combustion gas in the coolant.

So...I don't know if the first time the top radiator hose blew off was a cause or a symptom of high system pressure, but I have a definite problem and have to decide if I try some Blue Devil head gasket sealer or bite the bullet and replace the head gaskets.

How big a job is it to replace head gaskets on a Super V8? And has anyone tried Blue Devil head gasket sealer on one of our V8 engines?

 

Sorry to see that you have serious overheating issues Phil.

Nothing to lose by trying a sealant of some kind however I would regard that as a "temporary" fix and would not be confident of the fix on a long trip.

The other question I would have could there be any other damage to the engine block at all with such overheating?

If it were me I would seriously consider replacing the engine with a lower mileage one with a warranty. I see some on Ebay with a 6 month warranty.

By the time you have dismantled all that is required to get the cylinder heads off you have done 2/3rds the work involved in getting an engine out?

A compression test on all cylinders would maybe give an idea how bad the leak(s) are and whether both heads are affected. That would sway my opinion.

 

Not what I was hoping to hear, but I appreciate the honest answer. Other than the pressure buildup, the car runs well with no misfire codes. I drove it to town Thursday and when I checked this morning the coolant was down perhaps 1/16 to 1/8 inch or just below the rounded edge at the top of the max step in the expansion tank and there was still residual pressure so the leak appears to be one way. Got to look up head gaskets in the manual; Are they something a reasonably equipped DIY retired engineer could do by himself? Would you ever change just one head gasket?

Guess a leak down test of each cylinder is the next step per your suggestion or perhaps pressure each cylinder and watch for bubbles through the block tester at the expansion tank. The block tester instructions suggest removing the plug wires from one bank at a time and running the engine it to see if one or the other bank alone produces hydrocarbons in the coolant, but I think a leak down test would be more definitive. I did note that if I reved the engine to 2000 RPM with the block tester in place, that bubbles would come up through it on deceleration.

 

I would replace both gaskets while I was at it. I would hate to have to go thru a lot of the same work to get at the 2nd head gasket if after replacing just one the 2nd gave out later.

I would get both heads machined while I was at it as well.

 

Phil
Apart from maybe head gasket issues, you may also have flow issues in your cooling circuit (leaks, overpressure) that should be addressed.
Maybe some clogging or gunk somewhere.

 

As I stated on the Jaguar Lovers forum......


motorcarman
3h

The ‘real world’ labor time is about 24 Hours for a 4.2 Supercharged X350 to replace cylinder head gaskets, ENGINE SET.
Jaguar Warranty time is 16.2 hours but unless you perform the task several times in a row, you will not come CLOSE to 16.2 hours!!! That is why 24 hours is more realistic.
You will need the timing tools to lock the crank/cams for reassembly.
I doubt that a ‘can-of-motor-new’ will help with your situation.
bob

 

What is the labor time for engine removal and installation?

 

Look at it this way.
If you replace the engine with a used warranty one, can you be sure it won't fail with the same thing in 7 months time, or something worse.

If you replace BOTH head gaskets and all the other associated gaskets/rubbers/hoses that come in the kit, then you know it is all done and done properly, to your liking.
And I can more or less guarantee that you will replace other stuff that you just don't like the look of, or would be prudent to replace while you are in there.

 

I just replaced the engine in a 2004 X100 and the labor was 20 hours, including swapping ancillary parts.

The used engine was around $2000.

bob

 

My 04 VDP started having overwhelming compression problems, making the car undriveable, because of head gasket leaks. This had been happening for quite a while, but I managed to get 251k miles out of her. I tried a good brand of repair sealer through the radiator, and it helped for a short period of time. I was getting emissions problems with fouled oxygen sensors and fuel injectors, missing cylinders, and a clogged cat. I changed all that stuff out twice (incl. spark plugs), which kept her going. My local reliable shop wanted $3,800 to replace the head gaskets and ancillary stuff. It was a no-brainer for me to invest that cost in a much lower mileage (87k), same year/same model. The shop bought her from me for cheap as a fixer-upper. As loyal as I was and determined to get at least 350k on her, I'm glad I let her go instead of paying for the repair.

 

For me, the "head gasket fixer in a bottle" is a last resort before scrapping the whole engine. You really have no control over where it settles. It could easily not fix your head gasket leak, but clog up your coolant passages. I almost used some on my son's Ford Probe last spring, but I ended up replacing the head gasket myself. It's only a N/A 4 cylinder, so not quite as big as a job as your super V8. However, if you have the time and desire to give it a try, I say go for it.

It's not brain surgery, just a lot of tedious work....You just need to stay organized. Label everything and get a bunch of containers (I used sandwich bags) to keep the fasteners organized. When in doubt, take pictures to reference later on.

 

Thanks for all the input. I am still on the fence about what to do next and in the mean time emailed Blue Devil tech with some questions like could it be effective when the leak seems to be into the cooling system and not the other way, and the difference between the concentrate and Pour-N-Go. Here's what he said.

"We manufacture two different head gasket sealers; the directions are different for each. The "Pour N Go" (16 oz./white label) is a less concentrated formula that does not require the removal of the thermostat or a flush of the cooling system prior to use. Whereas the "Mechanic Approved" (32 oz./yellow label) requires both the removal of thermostat and a flush before applying the product; the 32 ounce is the more concentrated formula. The product with the yellow label will give you best overall results as long as you can remove the thermostat and flush the system prior to use. With the use of either product you will want to use 32 ounces to treat your Jaguar.
To give yourself the best overall chance of BlueDevil working successfully is to remove the spark plug from the cylinder with the leak; this will be the spark plug from the cylinder with the low compression reading. If you are not sure which one that is, you may pull all of the spark plugs and will notice one will have a white-crystal-like substance on it and/or may look dirty; this is the plug you should pull. Leave the plug out for the 50 minute idle in order to relieve the pressure from building up and thus allowing the product to seal properly. If your vehicle only has a reservoir/overflow rather than a radiator cap, instead of pouring BlueDevil through the reservoir/overflow, with the car off and engine cold you should disconnect the top radiator hose and add the product there; do not pour it into the reservoir. It may be added into the hose or the opening on the radiator. Once BlueDevil has been added, reconnect the hose and start the idle from that point."


I also emailed a relatively new outfit that sells BearsLeak (Get it? A play on Bar's leaks) that offers a similar blue chemical head gasket sealer before I did the block leak test, and they recommended doing the test and if positive doing a similar flush, fill, and idle with two 32 ounce bottles of their product. They claim to have the best instructions in the market but, strangely, I couldn’t find those instructions on their web site.


An interesting side note is that I compared the before and after block leak test fluid side by side in identical shot glasses, and I left the “after” fluid in its shot glass on a bathroom shelf. A week later it had returned to the pre-test blue color and was perhaps even a little darker blue than before.

 

Phil -- with this thread a few years old, I'm curious what decision you made and how it worked out. Did you try Blue Devil, or did you have the gaskets replaced? Thanks,
- scooter