Hello everybody...one week ago I bought a 2004 xj8 with a blown head gasket. The previous owner mechanic told me the car is blowing exhaust in the cooling system and pushed the upper hose from radiator.
I have no idea how long the car was driven while overheating. What I do know is that when it happened, the owner went directly to a mechanic, who diagnosed the blown head gasket. Also I have no idea why the car overheated. The car actually turns on but it's obviously running only on 7 cylinders.
The car has 93k original miles, and I bought it to be a donor for another 2005 xj8 (with 116k miles on it now) that I acquired one year ago and is actually my daily driver. Lately this one was giving me once in while a hard shifting from 3rd to 2nd, so the purpose was to get parts and eventually a transmission.
The 2004 is in very good condition except for the head gasket. This is why I'm thinking about fixing it, may be trying to cycle in the engine one of these gasket sealers, like steel sealer or blue devil, or maybe to fix the head gasket by myself.
Does anybody have a suggestion about any of these gasket sealers? Are there any tutorials about how to replace the head gasket?
Thank you for any help.

Snake oil is what the Blue Devil is trying to sell you, I M H O

There is no additive that can fix a blown head gasket (or overhaul an engine). Better to spend the money on a compression tester for your toolbox.

Have you verified that it IS a head gasket?
Just to be sure what problem that engine does have?
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Actually that is a great question. I reread the initial post and realized I had just jumped on the “blown head gasket” train. However, is there water in your oil or oil in the water? The upper hose coming off may not been caused by exhaust pressure in the cooling system. Actually I have never had that as a symptom from a head gasket. Also a bad miss may well be the result of coolant being sprayed all over the engine from the hose failure.

I would not start an engine if there is water in the oil, however if there is no indication of water (your oil could look creamy) or depending on the circumstances you may need to loosen the drain plug. Water will drip out before any oil so be very careful when loosening the drain.

You should look for any stored engine codes as I would think the high engine temperature should be recorded. I do not have my ELM reader handy to see what my car shows when the engine is not running.

If there is no contamination and you can replace the hose and put in coolant, I would try a compression test before pulling a head.

Good luck, it sounds like a rewarding project that while daunting is not beyond a DIY individual.

I agree on a pressure test but if the top hose blew off odds are there is a head gasket related issue.

Unless it was a bad hose. I would not expect a hose to be "blown off" unless there was a clamp or some other failure. It should have just been ruptured. My 2004 has the original hoses on it and I try to check them regularly (usually after I read a post like this one). There is not really any information about the history of the car. Regardless if it was ran while overheated the head gasket may be shot. I have not really heard or read anything about the 4.2 having any head weaknesses but I have had past issues with cracks in other engine heads. Especially with the high compression designs like the 4.2 NA. Or perhaps I should say with engines that have high compression, unfortunately most of those engines were not designed for actual high compression from the factory which the Jaguar was. I do not expect any issues with the head unless it has been damaged by high temps.

I suppose at this point, other than determining which head is affected, the work needed will be basically the same.

Basically I went to pick the car up from the mechanic the owner was there and they said the gasket was blown.
It is not any water in the oil, not any sign of contamination, he said the exhaust gas is going trough the cooling system and popping out the upper hose.
the car was driven from the wife of the owner and I imagined something happened and may be for some reason overheated.
is it possible the house is popping out because of the water pump or the thermostat not working properly?
car start immediately not white fumes not any sign ( may be because has no coolant in it) and it is running 7 cyl.
later today I will connect the tester and I will let you know the codes.
thank you for all your suggestions.

Well to me it would be worth testing the coolant for exhaust gases. Replacing a head gasket is so expensive I want to be 100% what the problem is before attempting any repair.
But let us know how it turns out for sure.
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I ordered a exhaust leak tester and during the week end I will connect the hose and I will fill the radiator with water and I will make the test.
In the worst scenario i think I will proceed to replace the head gasket by myself, I usually take care of the ordinary maintenance by myself, I have space, tools and time and I hope to be able to fix the car.

Blue Devil is the only "pour in fix" I have ever seen actually work, twice. I have no idea if this is an anomaly I witnessed by some exception, yet I was in a tight spot with a V10 ford 1 ton truck, obviously blown and simply poured it in. It WORKED. I continued to drive the truck for 2 years, and with 24,000 lbs on a gooseneck behind it mostly. I **** you not. And on a sailboat in the bahamas, poured it in off Bimini and used the yanmar diesel off and on for a year then sold the boat (imparting this knowledge) and I the buyer motored from south florida to almost new york and continued to use the engine for years....
That's all I know, it is worth a shot and I don't think it hurts the engine if put in it for the wrong issue. I'm not positive of that. I'm just not a fan of pour in fix in a bottle bullshit yet I have seen Blue Devil work. period. Heck with all the rest, unless someone has a story ....

Speak of the Blue Devil, actually, that product, if used correctly and following the instructions, gives excellent results, so long as the gasket leak is not a major one (and sometimes even if it is). Plenty of testimonials for it on YouTube. My tech, as well as my tow truck driver (who drove me home when Superblue blew hers) also stand by that product. In fact, there is a link somewhere on here to 2autoguys' (?) website where they say that, although they generally do not approve of "pour in" products as a "fix", they have found the B.D. product to yield good results. Well worth giving it a try before spending $Ks for a mechanical repair.