Hi forum, i had plenty of issues and still do like overheating, losing power when slightly hotter then normal . Im doing another overhaul now, rewiring harness, replacing both crank speed sensors etc.
But since i bought the car, i could feel a very light vibration at idle and in drive, you can feel it only when car is not moving, and that vibration was coming every 3-4 seconds or so.Tailpipes didnt give out anything, both banks felt the same .
All injectors was cleaned and tested, all of them was clicking the same, new spark plugs, spark wires, dist cap, coils, 1/2 amplifiers etc
now i pulled out all spark plugs to do a compression test
here are results
b1- 210
b2 - 200
b3 - 195
b4 - 210
b5 - 205
b6 - 205
a1 - 192
a2 - 205
a3 - 195
a4 - 205
a5 - 200
a6 - 205

Not sure if those figures are within normal, are they?

so here is a pic of all spark plugs , they have less then 40 miles on them
You can see that all of them are even, except two (b2 and b6)
Does it ring a bell to anyone? What could be the issue?

Thank you

 

Compression results look good.

From the plugs I'd say you're running a bit rich, with two cylinders not quite as rich as the others.

Was the 40 miles of driving was mostly short trip/cold engine?

Cheers
DD

 

hi Doug, i also just realised i forgot to open throttle bodies when doing compression, so they are even higher.

regarding running too reach, yeah, i had a vacuum leak in vacuum line going to ECU, so i assume i was running too rich because of that, that 40 miles was mostly on hot engine, since i was fighting overheating.

my concern is why 2 plugs are off, and could that be a clue to any additional checks, as im running out of the ideas what to check by now.

 

Those white tips are a sign your engine is runnign hot. Two plugs show that clearly and a few others have the beginnings of that. I'd do a full check / service of the cooling system, those hot cylinders are candidates for a valve seat drop.

 

cooling system was entirely overhauled twice, every single component checked, replaced, checked again. That’s why I’m working on crankshaft sensors , rewiring, etc, as I suspect misfire or other sort of mechanical issue that leads to overheating. You say candidates of dropped valve seats, how do I check that, wouldn’t dropped seat valves affect compression?

 

Maybe those spark plugs are a clue to your cooling issues? A blockage or air pocket around those cylinders perhaps?

 

Valve seats drop when the engine / cylinder gets unusually hot. If the seat drops out of the head... your engine is scrap.

Why was the cooling system overhauled 2x ?
A misfire wont make an engine overheat per se, It can cause unburned fuel to over work the converter. Then the converter can be damaged and get red hot but that wont show up in the cooling system.

 

sorry was busy ordering more parts for xjs (joking..or not?)
system was overhauled twice because it still overheats(or not?) also it loosing power when it gets too hot. I have run out of the ideas why it overheats so decided to check compression and etc as i can feel some very light vibration at idle that comes and goes with specific intervals.
car overheats at speed more.

 

I'm not sure what you already tried but...
Take BOTH thermostats out and see if it still over heats. You can also put them in some boiling water to make sure they are opening.

You can also get a exhaust gas test kit for the cooling system from the Jungle Website for 25$ and verify there are no exhaust gasses entering the cooling system.

 

i should have done it prior to posting, my bad, here is a list of what has been done
radiator recored 2 times
all new hoses
new thermostats of correct length , checked in the pan with boiling water
new heater valve
all vacuum lines new
tried 2 fan clutches (new)
switched to electric fan controlleb by thermoswitch
verified the small oem fun
all holes around rad is plugged,
coolant drained refilled at least 5 times using 5 different methods to purge air
metal tank, removed, cleaned, inspected, painted
plastic tank, removed, cleaned, inspected, preffiled
new water pump
all new belts
rails removed, cleaned, metal pipes replaced, as well as all round seals
cooling system pressure tested

yes, coolant system is tested for exhaust gases (negative)
also no sign of any milkshakes, no exhaust smoke


Problems i have now
- overaheats while driving (slow, fast- faster)
- slight vibration at idle
- car looses power when too hot (above N)

Problems that are found by now
ECU vacuum line was rusted near the rear wheel , i cut it and replaced with silicon hose, but when i pressure test the line it still looses pressure.

What was done to engine top
CTS and Air sensor resistance tested at the sensors and in the ecu
new dist cap
new spark plug wires
1/2 new coil
1/2 new amplifier
coolant gauge sensor - works correctly
all new filters
and tens of other things
injectors removed, cleaned , serviced
injectors clicking (tested)


what will do next
waiting both new Crank speed sensors
installing fuel pressure gauge
ordered coolant glass filters to monitor the flow
ordered thermocouples to watch temperature at both radiator bolts
checking the wiring (unfortinately it looks OK, but will rewire some parts)
bought another ECU (it was a good deal)
DRIVED THE CAR LESS THEN 20 MILES
TIRED

 

In the list of all the work you have done, I didn't see that the heater matrix and engine block were flushed or flow tested. Let me ask a couple of questions:

Was the car ever not driven for an extended period of time?

Does the heater work (I mean really work)?

The stock system doesn't need any modification to properly cool the V12, so my concern is that any modifications will only mask a fundamental flaw, and the only thing I can think of that seems to fit what you have described is a blockage of a coolant passageway or heater matrix. Normally, a new coolant flush will work, but not always. There is also the notorious factory recommendation to use Barr's Leak.

The other possibility is the air purge system, is a pipe blocked? Has the modification of the Banjo Bolts per "The Book" been done, or are overly thick crush washers being used?

Here is the section regarding the air purge system:

RADIATOR AIR PURGE SYSTEM: Across the top of the upper support rail is a tubing assembly for purging air out of the cooling system, and it's attached to the radiator at a banjo fitting at the top right. This banjo fitting has a design defect in that the hole through the side of the bolt itself is too close to the head, so it doesn't line up with the annular groove in the fitting properly. This exact same flaw is found in the banjo bolts on the back end of the tappet blocks and is discussed at length; the same modification should be done here to improve flow and make sure the air purge system works as intended. The banjo fitting on the radiator is longer and has finer threads than those on the tappet blocks, but it is the same diameter.

Using thick copper seals under the head makes the hole misalignment worse, so Jaguar provides really thin seals that tend to leak. Once the modification to the bolt is done, the thick seals commonly found in auto parts stores can be used for better sealing. This banjo fitting requires three seals, and the plug at the top left for venting the radiator when changing coolant requires one more of the same size. If your local auto parts store has a rack of red cards titled "Help!", it probably has a package of sealing washers that are perfect for these fittings: part number 66272, labelled "Brake Hose Bolt Washer". It says they are ID 25/64" and OD 5/8".

Hope this helps.

 

Thank you!
Please keep in mind that its my first car project and i didnt do any mechanical work before, so i was learning as i go. So obviously i could do smth wrong.

Now answering your question one by one
-heater matrix and engine block was flushed with garden hose, no debris visible and water was going in and out, i dont know if one of the engine block passages would be block how could i know it?
-no idea what was with the car prior to buying it, i bought it overseas
- heater works, at least i can turn heater on/off from the cabin
- all pipes was removed, cleaned, so they are not blocked for sure
- modified banjo bolt i bought new from a well know ebay seller, the only thing i dont know, when installing this new banjo bolt, do you need to somehow align the banjo bolt hole? i just tighten it up, and thats it.

 

Another question, is the front 'chin' spoiler installed on your car?

 

yes it is/

 

You've done so much admirable work so far, that I really hesitate to recommend more, but I found this photo you posted of your engine:




Based on where the arrow points, I think it is highly likely that you will have hard scale or spent coolant deposits in the block.

Here is a thread with photos of how bad it can get if a car isn't driven or the coolant isn't changed:

https://forums.jag-lovers.com/t/1976...crud/436006/23

Unfortunately, deposits like that can't be flushed with an ambient temperature garden hose. Old coolant deposits requires boiling water, and depending on the type of other scale some kind of chemical intervention. Most consumer flush products like Prestone are pretty mild (for obvious liability reasons) but may not be much help. There is a product available in the US called ThoroFlush that I recall someone reporting that it was the only thing that worked to get all the rust, scale and Barr's Leak out of his engine. Here is an Amazon link for ThoroFlush:



I don't know if is available in Europe, but hopefully someone on your side of the pond will have a recommendation of one that is effective, but also safe with the alloys used in the V12.

I would recommend that you DO NOT use a chemical flush on the whole system. You don't want it to loosen rust and deposits and then clog your heater core and your radiator. Separate the system into three parts -- engine block, heater core and radiator. In your case I would not do anything with your radiator since it's been re-cored. When flushing the heater core do it in the opposite direction of normal flow so it less likely to get further clogged, and more likely to release existing clogs.

I don't know if this is definitely your issue, but it would be good to eliminate it as possible culprit. It's the only thing I can think of that would cause individual cylinders to overheat compared to others other than air pockets.

 

Fully agree, i had thoughts on that, but never took them serious.

Only question is how do i flush the block with disconnected heater part and radiator using the chemical flush? im trying to think how to do it and i cant really see it , most of this flush chemicals requiring engine to run.

 

Be careful with ANY chemical flush. Be sure it is listed as safe for aluminum block/head engines. Some are not safe.

 

Good question, and I've never had to deal with an engine blockage so I'm no expert. Hopefully someone else will chime in.

However, what I think you could do is replace the two heater hoses with one that loops back into the block. Disconnect the radiator hoses. Then take two 5 gallon buckets, one with fresh flush fluid and the other for discharge. A pump might be handy to fill the block or you could pour it manually. I would assume you would fill at the upper hose and discharge from the lower so gravity is working for you. Perhaps block off the lower hose, fill and let the flush work for a bit, repeat a few times? Then flush with distilled water.

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