This is my 1st posting on Jaguar Forums. I bought a 2000 XK8 off an internet auction site. I started having overheating and eventually the engine totally shutting down and then restarting after a cool down period just to shut down again upon overheating. I changed the timing chain tensioners, water pump, etc... While this was being done I discovered a VERY THICK hard powdery build up in the hoses that go into the heads and the hose that attaches to the thermostat housing. Does anyone know what this is OR what may have been the cause of it OR what I can use to neutralize it so it can be removed? I have attached some pics so a visual can be imprinted. This is VERY odd to me. I have been piddle paddling with cars (old school types) pretty much my entire adult life (not certified by any means but I consider my skills somewhat knowledgeable) and I have never encountered something of this nature. Thank you for ANY tips, advice or helpful solutions.

 

That is really strange, like someone put a lot of that old school radiator stop leak in the system like Silver Seal or kept adding some really nasty water with a lot of iron in it. I would expect to find a red Jelled buildup at the high points if anything. The OAT Coolant that Jaguar uses tends to form a redish Gell buildup with age that collects at the high points in the system. It looks like your due for some serious back flushing.

 

Mixing of antifreeze types can result in formation of a precipitate. You have to assume the radiator and heater as well as the engine are blocked, either from antifreeze issue, leak fix gunk, or some other source. I don't know if any typical coolant system flush will help, but I doubt it.

It is essential that you do not overheat the engine. Blown head gaskets, damage to the nikasil linings and dropped valve seats are typical damage from overheating.

I would talk to a radiator repair shop and possibly have it towed there. Do not go to a Jag dealer as they will want to replace the engine and cooling system.

 

+1 on the above. Jaguar specifically warns about mixing non Jaguar spec coolant with the Jaguar recommended coolant because of "gelling".

 

Wow! I've seen gelling before but never a hard accumulation like that....

Almost looks like an ocean-living crustacean building up his shell via the excretion process. If you find any oysters in your cooling system, I surely would not eat them....

 

thanks for the replies, This has been another let down... Just completed changing out all timing chains, therm, water pump , plugs. although have this build up and restricted, I still have circulation, the motor starts and runs smooth til in increase rpm then shuts down.did a hard reset on ECM, removed all codes, re-ran BBA 2 and still have P0010 circuit malf.P0102 p0335ckps circuit malf, P0336 ckps range/performance, P0447 ???, P1000, P1144 AACV assist close valve circuit malf, and P1341 CMPS pulse not detected at CKPS, missing tooth??? I live in a rural area in Texas and have 2 of the best mechanics in area look at it and scratch there heads...I really need some help on this, I want to get it running and do a complete restore, it a car with a lot of class and would like to see it running and back on the street....thanks for any assistance with getting it done.

 

Whenever I see a car with several unrelated codes I think a check of the ECU is called for.

ECUs of this era had electrolytic capacitors susceptible to the capacitor plague (See https://en.wikipedia.org/wiki/Capacitor_plague) which could lead to shorts, opens, and corrosion on the ECU circuit board. If you remove the ECU there would usually be visual evidence of this, which would be brown or black spots, wetness and corroded metalization on the circuit board. You can send the ECU to be rebuilt by Automotive Scientific Inc. | Quality Rebuilt Automotive Electronics | Rogersville, TN.

You can also just send it to ASI to have it tested to be sure it is good for a relativity small fee. Knowing it is good is helpful when diagnosing multiple issues.

 

Just after I bought my 98 XK8 I changed the thermostat and installed the aluminum housing. I found the antifreeze looked like this, very chalky, milky, with deposits inside the old housing and hoses, but not as thick as yours. I used a flushing agent, twice, and I managed to get it all out. Dam stuff stained my blacktop too, pressure wash wouldn't move it, took a whole winter of ice and snow to remove it!
It may help, try a slightly caustic flush and allow it to soak for a while, then see if it'll wash out.
Regards,

 

I'd be afraid flushing it would damage the water pump if that stuff broke up while running. I'd take the pump out of the loop and soak it with some form of cleaning agent a few times overnight.

 

Could possibly be silicate drop out due to non oat antifreeze being used and not changed at the two year interval. I used to see this regularly on trucks in the U.K. - first sign was usually overheating at the start of summer when the ambient temperature rose.

 

Not sure how to help on this one. I would have the ECM checked as Steve suggested I would also flush the coolant system. Remember that the throttle body also has the coolant flowing through it and that might have an impact on the codes you are getting if the flow is restricted.

I have never seen a buildup of stuff like I am seeing on your car I can only say it looks bad. I would check on a type of flush that would do the job and not harm the engine block and all the other stuff like the radiator. You do not want to cause a blockage in that radiator. You may want to check with a shop that specializes in the coolant system.

 

posted wrong location

 

Break a chunk off. Add a couple of drops of vinegar on it. See if it bubbles. That looks so much like hard water contamination. I think someone had a leak and kept adding tap water to it.

Bit like this pipe.



I also agree with the above comments too. Wrong sort of anti freeze.

You can also create what I call damage by maintenance. Who knows what holes that stuff is blocking. You may get rid of it only to find a load of leaks. Personally Id change what hoses I could. Stick some engine flush in it and let it circulate. Leave it for a week. Remove the pump. Stick a hose in the top and flush it through for a couple of hours or so. Try white distilled vinegar to clean out the pump. Cheap but effective.

 

Lots of great info on this forum.. (Working to get my ten messages in since I am a new member)

 

"Hardening of the arteries." No vehicle is immune. Like Muttray, I'm coming late to this party, and am a newbie working towards 10 postings. My comments won't help mikiep now but who knows when the "plaque" will build up in another Jaguar and the owner will be coming here looking for a cure.

Wouldn't hurt to check pH if any of the suspect coolant is still available.

frankc is on the right track, test a chunk with full strength vinegar to see if it bubbles and dissolves. A weakly acidic vinegar solution could slowly undo the buildup.

For those paranoid about acid inside an aluminum engine, just run pure water (weather permitting) and go without antifreeze for a while. (Bear in mind, cold weather can freeze it and extremely hot conditions can lead to earlier boiling than running antifreeze). Driving will circulate very hot water while driving, and whatever that precipitate is should have some tendency to go back into solution. Distilled water should be a touch purer than tap water but now we'd just be splitting hairs. For those scientists and chemists who own Jags, you understand there could be traces of chlorine, fluorine, trace minerals, calcium carbonate keeping it a bit basic, etc... you'd probably go searching for demineralized water or H2O filtered by reverse osmosis.

And whatever you do, do not go down that path of waterless coolant if you want you engine to last.

In my opinion, other than removing old coolant, cold water "flushes" are pretty lame for removing any tenacious "clingons." I devised my own idea of a violent flush for my wife's MG TD. You may not want to try this at home boys and girls. After draining radiator and block, I dumped in a quart or two of water (and left radiator cap off), ducked down for cover beside the running board and then used an air gun to blast compressed air into the engine drain. The first shot produced a volcano of brown water with some sludge shooting straight up all over everything in the vicinity. What a mess! Subsequent water baths became progressively cleaner, though.