The Notorious Stop-Leak Instructions

I have found the section in the factory manual for the Jaguar XJ-S, purchased around 7 years ago, that includes the instructions which have doomed the bottom halves of many an OEM radiator and presumably contributed to the reputation for running hot and overheating these cars have been saddled with. It doesn’t out and out say to use stop-leak in your jag every time you change the coolant, but 14 oz of leak inhibitor being noted as a standard component of a fluid service might just lead some people to believe you’re supposed to use stop leak whenever you change the coolant.

Yes, this is the most shitty corrective action to clumsy UK design I have ever seen. Tear this bit away and use after upcoming lunch… The crap they’re recommending to pour in. It’s like making sure you will be coming back to the workshop…

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XJ even worse - they got other things wrong too but this is particularly bad.

Oh wow, that is even worse. I guess that’s one way to do planned obsolescence

I wonder if this could help lead to dropped valve seats? Not only do the radiator passages get narrowed, but passages in the head too?

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That stuff has been around for years, and I admit to using it to temporarily fix a leak in a radiator. It did disastrous work on the heater core, clogging it up completely.
Now, on to modern times: Cadillac had a common problem with their mostly aluminum engines in the 80’s, and short of pulling the heads for blown gaskets, they offered a ‘fix’ in a little plastic tube, that you could purchase at the parts counter at GM dealers. I was told it was ground-up wings and parts from a beetle. This proves that high technology has been around for some time.

I wondered why I don’t seem to see very many VW’s around anymore.

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Someone told me a great temp fix for a leaking radiator, water pump, etc…pepper! It will stop the leak so you can get home, and will easily clean out.

There’s a story about using an egg, too.

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You know , last year I heard about that story about pepper. So I dumped about two or three capfuls into my 2002 Jeep Liberty to stop a leak. The Liberty didn’t really have a radiator cap , at least one I could find. So I dumped it into the overflow top up tank . After about an hour of going into the store and coming out the tank got plugged , exploded in the parking lot , never sure it ever got to the radiator but a $1000 later had to replace the radiator and tank anyway.
Last note, it did plug some holes for sure.

Way back when my first t had a very leaking radiator. Solution, a big can of water. or stop at a gas station. water was free.

Much pleased when one of Dad’s friends sold him a pristine T radiator for two bucks. The beginning. it was for a 27, and my car was a 23. The 27 a tad taller. but, with a shiny nickle shell!!! At first, just omit the hood. Then, swap bodies for a 27 Roadster !!!

Off the frame restore… Red chassis, grey engine. grey body, red wheels…

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My favorite myth is the one about the GM stop-leak for all aluminum engines that had leaky head gaskets. Small plastic tube with brown powder is supposed to be ground-up beetle wings and such. It may be true, and I have heard of people using oat meal in Model A fords.

Yep, use that stuff and you’ll soon be “sacheting” off to the repair shop with your XJS. :grimacing:

btw, for those of you who are “fans” of my tech/ex-roommate, you may be interested to know that his 2000 GM Yukon got stolen the other day (yep, he leant it out to someone he shouldn’t have entrusted it to :face_with_raised_eyebrow: ) but recovered it a couple of weeks later, courtesy of the Dallas P.D. :policeman: However, when he went to pick it up at the city pound he was devastated to learn it had been stripped before being abandoned. :cry: Anyway, also, b/c there was a leaky water pump in his SUV, the perp drove it until it apparently overheated before abandoning it, resulting in what we believe to be a blown head gasket (blowing steam out the pipes and oily grime on inside of radiator cap, but no oil in coolant or vice versa though, so no cracked head or block, apparently :relieved: ). He decided to go with one of those liquid products that supposedly “repairs” blown head gaskets, which is highly touted on YouTube by reviewers. However, of course, he did NOT follow the directions on the can as to removing the thermos, flushing the system, replacing the thermos housings and SLOWLY pouring the stuff in while the engine is running (or idling it for an hour before shutting off). Instead, he did the “dump and go” (apparently paying too much credence to the title on the FRONT of the bottle) and idled it for only 15 or so minutes. :exploding_head: So, of course the attempt failed. :-1: After I made him watch a few YouTube videos on how to CORRECTLY use the product, he went and bought another bottle (another $35.00) but now his Yukon won’t even fire up. I told him that it has probably hydro-locked now, and just kiss the engine goodbye. I still can’t believe I let this guy work on my Jags … :crazy_face:

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Haven’t found a shop with the patience or the attention to detail, but I did swap in a new oversized aluminum radiator and a silicone hose kit, after I followed the book’s instructions and rusted out the bottom of my radiator thereby stranding myself hours from home with a badly overheating big cat, of course. Thankfully no valve seat dropping occurred, but I’ve made a point of treating the car a bit better since then.

Remove the spark plugs and crank. Gushjer???

That’s my guess on what he ought to try … :bulb:

I should clarify that I got a tow as soon as the temps climbed above N and had a good shop do what they could for it, and that the radiator rusted out later when the car sat for a while. I worded that previous post quite poorly, and it might lead someone to believe you can actually get away with driving these cars any distance when the temperatures are above the N, or that I in fact did. You cannot, and I didn’t, and that seems to be why the thing still starts and runs many parts and many, many hours later.

Stop leak products of different varieties can maybe sometimes work if used as directed in certain desperate or manufacturer-specified applications, as mentioned by previous posters. The Jaguar v12 is not and should never be one of those applications unless maybe if you actually see a stream of coolant pouring out of your radiator and don’t mind a fix that constrains your car to about 60mph tops and runs the risk of overheating the bank of cylinders that doesn’t have a temp sensor while indicating normal temps and potentially dropping exhaust valve seats.

As much as the addition of stop-leak did absolutely ruin the radiator over time, in the short term it did leak a bit less coolant and the car was fine as long as you stayed away from highways. However, it would have never needed a radiator if I’d just left well enough alone and gotten used to pouring in coolant every couple hundred miles, so hopefully it’s clear that the point of this is that while some products may work in some cars when used as directed, you should really avoid any sort of additive besides the recommended amount of ethylene glycol in the cooling system of a jaguar v12. They’re not supposed to leak, but if and when they do you’re better off adding coolant or changing parts than using a quick fix that will cost you in the long run. In the off chance someone finds this who is considering going the route I did, blindly trusts the repair manual, and hasn’t encountered Experience in a Book, just say no to stop leak or be prepared to have a hobbled car that needs expensive parts soon. Also, consult Experience in a Book. Might save you a radiator and some other bits.

There HAD to be a use for the miserable little PsOS…:crazy_face: