Hi All,
noticed a strange phenomenon yesterday - a little pool of rusty water in the recess just behind the foremost spark plug. The car’s been in the garage dry so not sure where that’s come from. And today noticed a sort of Crystal like smattering across the cam cover.

Does anyone know what could be causing this?

Thanks a lot, Al.

 

I don't know but I'd deffinetly wear a mask when you clean it up. You don't want to be breathing that stuff.

 

I knew I'd seen that stuff before. May be Lichen that grows on bricks and trees in shady damp places.

 

use a vacuum cleaner, looks like dry coolant mixed with something else, maybe a sealer, and coming out of the rusty plug. Run the engine to tenperature to see if it spurts out through the plug.

 

Cleaned out area and replaced plugs today, then run up to temperature and noticed a little liquid pool in this small round circle in between the front two plugs,

it’s a bit strange as I can’t see how it could get there!

any ideas?

thanks a lot, Al

 

A nearby head bolt is weeping ?

Carl

 

the plug is called a Freeze Plug. Replace it.

 

Hi awg294,

As Jose has pointed out you have a weeping freeze plug which we sometimes call a welch plug in Oz. (Others call it a core plug as well)

They are a legacy of sand casting.

Brass is what proper ones are made of and there are three of them in the valley of your head.

When you remove it, make sure it doesn't drop into the head as it will then be in the water gallery and will only block part of it up (Not good).

When I removed one of my weeping ones I was able to carefully knock it out with some force with a large screwdriver.

As their exterior walls are slightly tapered, refitting a new one is relatively straight forward and I smeared some gasket goo on the surfaces for good measure.

The weeping will get progressively worse until the weakened material (water in the gallery corroding the metal plug from the inside) literally springs a leak as mine did in heavy traffic way back when.

I suggest you fix your now before it becomes rather more urgent.

Good luck,

Nigel

 

All great advice above.
If one is going... the others are likely not far behind. Perhaps wise to do all three and try to find brass replacements, if possible. Corrosion of this type is usually a symptom of coolant that is too weak. The dissimilar metals of our engines (cast iron block and alloy head) when filled with conductive liquid (coolant) and part of a negative earth ignition system can be prone to electrolytic corrosion. The (usually) ethylene glycol that is addded to water to form our coolant should be 50:50 mono ethylene glycol and demineralized (not tap because of other chemicals present) water. Many other motor manufacturers specify 30% glycol concentrations and the "pre-mix" coolants on retail sale are often at this rate. For this reason, it is generally safer to buy the concentrate and mix it yourself. Unfortunately, while glycol at the correct concentration acts to retard corrosion, at a "weak" (for our cars 30% is considered weak) it actually promotes and accelerates corrosion - eventually likely leading to head gasket failure. If I saw a customer's car with a failing freeze/welch plug in that state, I would certainly be asking permission to replace all three and would be checking the PH levels of their coolant to deermine density.

 

imperialmotors,

50/50 is the minimum I would do, I always do 60/40, (6 quarts coolant and 4 quarts water mix) which gives me approximately 2 gallons of mix, the XJ requires an enormous amount of coolant. And no sealer of any kind, they clog the cooling system.

and yes, I never buy the pre-mixed product.

 

I agree, 50/50 minimum but I do it differently. I flush thoroughly with tap water, drain and then flush again with distilled water, then drain. Next step is to look up exactly what the capacity of the coolant system is (making sure about US gallons vs Imperial gallons). Then I pour in ½ The capacity of pure un-diluted antifreeze (making sure you use the recommend type, one of my cars uses red, another orange, and the others green). Then top it off with distilled water. The reason I do this is unless you open all the drain plugs including radiator and maybe more than one on the block, plus you'll never get the heater coil drained, then I am absolutely sure I have 50/50. If your not as compulsive as I am just use Jose's 60/40 method.

Jeff

 

Jose nailed it. Freeze plug. Familiar name, but incorrect. Not hard to deal with in that location.

Decades ago, one failed in our 58 Pontiac Star Chief. The pinnacle of art deco chrome barges!!! but, it was comfortable and quite fast.

Core plug at the rear of the left head began to leak profusely !!!! Pull the head? Lottsa of stuff involved Nope. got my drill and a hammer and chisel. I opened an an acess port. Standing on my head working just under the steering post!!! Pried it out

Set a new brass plug. Made a cover and attached it woirth self tap sheet metal fasteners. DONE !!!

Carl

 

Jose,
Good point about those awful sealant products too. I remember how many "discussions" were had back in the early 80's between the owner of the Jaguar dealership I was working at and customers who had taken it upon themselves to add a product called "Bars Leak" to their cooling systems as a preventative measure against leaks. Naturally, since our summer temperatures here routinely get up over the 100 degrees Fahrenheit mark, the clogging effect of the product generated predictable results and overheating of both customer and cylinder heads. I felt sorry for the customers though. Many of them had been loyal, long-tme Jaguar owners since the 1950's, then trading-in for a new Series 3 as their "retirement reward". When they got their, for example, new Mark 2, Jaguar used to advise adding sealant to the cooling system, but those were different days (and in retrospect, perhaps unwise advice even for that time). It shows the dangers of following past pratices that may no longer be relevant/effective in current technology. Of course, the owners had technically voided their new car warranties by adding the product. In the end, a group of us would do cylinder head swaps on Saturdays "at cost" for the customers affected (with the boss's knowledge and approval) which meant no rejected warranty claims, no loss of customer brand loyalty / reputation and retention of business for us and for Jaguar. That product is still on auto part supply store shelves here to this day...

 

inperialmotors, thanks I had forgotten the name Bar's but I have heard about it since the 1980's and the disasters it created. They should have named it Bar's Clog.

Carl, freeze plug is what they call them at Firestone and Good Year auto repair centers.
Core plugs, freeze plugs, welch plugs, expansion plugs, cup plugs, all the same thing. The aftermarket company DORMAN PRODUCTS makes or used to make a copper core plug that you tighten in place. It expands as you tighten it, has a 11mm nut in the center. A fraction smaller than the hole, you tap it into the hole, then tighten the nut. I have one since the 1980's, a gift from a mechanic replacing one in my Ford minivan who told me "don't tell the manager".

check this video: https://youtu.be/CkhBQQVJUlU