Thanks Sawyer, I’m making a list of all the things mentioned in this thread and i’ll add the things you highlighted and slowly work through them.
Another simple check would be to use an unlit propane torch, aimed at the carb bases, throttle shafts, and any areas of vacuum: leaks will show up as increases in engine speed.
Same applies to fuel injection. I’d want to do the head gasket if it goes, when it does. Would an engine mount rumble over rough roads?
It would transmit the vibrations…but with a proper setup, the engine would still idle smoothly.
Hi everyone, I just thought I’d update this situation so people might be able to learn from it.
When i originally posted this i had got differing opinions on what the cause of the rough idle was. Turns out the Jaguar mechanic was correct, it was a head gasket which 6 months ago was at the embryonic stage.
The car has certainly progressed past that stage as I have checked the dipstick and it has that milkshake appearance. Strange because the car certainly hasn’t been overheated over the last 6 months.
I’m thinking of trying Irontite Ceramic Motor Seal. The chances of it working aren’t good but i really don’t have anything to lose. I certainly won’t be repairing the engine.
I’ll keep everyone informed on how it goes.
**
But you should have been loosing coolant, Nick - as an added indication…?
Frank
xj6 85 Sov Europe (UK/NZ)
**
Hi Frank, 6 months ago, the car was losing 2 litres every 3 or 4 months. The loss was VERY gradual. Over recent weeks it has lost 2 litres over a week.
It doesn’t make any sense because 6 months ago, there was no other indication apart from the slight corrosion on the spark plug. I mean i checked for head gasket leak with that combustion chemical leak tester and it didn’t show up. I also checked for bubbles in the overflow bottle with the engine running and nothing. I even went as far as to do a leak down test and there was no bubbles in the overflow container when i pumped 100 psi into the cylinders. Very strange indeed.
**
Have you re-run the earlier tests recently, Nick…?
In principle; the head gasket can leak coolant in three ways:
- Into the cylinders. Showing up on a compression test, direct observation of coolant inside the cylinder(s) and indeed bubbling and exhaust smell in the coolant… It will also run down into the sump - r- and by viual external observationaising oil levels, and discolour oil.
2)Between water jacket and oil galleries. Showing up as loss of coolant, rising sump oil levels and discolouration of sump oil and maybe in the coolant. It is not detectable by compression test or pressurising cylinders. Applying pressure at the filler cap, a leak-down test, will conform a coolant leak - but not necessarily at the head gasket…
3)The head gasket leaking externally. Detectable by a leak-down test.
Point here is that only 1) will affect engine idle - but all three may be present. I think a re-examination is called for; your previous tests does not indicate a head gasket leak - and the uneven idle may have a different cause…
Pressurising the coolant system is pertinent for observing external leaks; as coolant heats and expands; system pressure increases - and external leak may not be detectable at atmospheric pressures…?
Using additives to seal leaks is fraught; at best it will have no effect - and it will over time impair coolant circulation. Besides; such additives will struggle to seal such a large leak, and will not work on such leaks between water jacket and cylinders - pressure and temps are too high…
As an aside; a leak from the radiator hose, like loose clamps may drip on to the dist lid - which will definitely affect engine running…
Frank
xj6 85 Sov Europe (UK/NZ)
**
1 Like
for $40 an engine oil analysis will show…or about the same for a test of coolant that shows exposure to exhaust gases.
Its worth cleaning the area around the water pump and checking very close for a leak, it dries on the block
Quick question - where and how? Casting failure or am I missing something?
**
Oil from the head drains through the gasket to the block oil galleries, David…?
Frank
xj6 85 Sov Europe (UK/NZ)
I’m still not sure how the oil from the head would get there. There are two cam feed lines, that oil pressurizes the bearings and from then on it is all splash lubrication until it runs down the front…? I can’t understand how it would ordinarily mix with the coolant, other than a casting failure.
got it. Either of the locations where the oil returns to the sump.
David
When the oil runs down the front, returning to the sump, it has to pass through the head gasket no?
Aristides
Thanks for the great input Frank.
I have to redo all the tests i did 6 months ago. Back then the compression tests showed all cylinders had roughly 150 psi. I think the results will be much different now as i feel the leak is in-between cylinders.
Whilst i have the spark plugs i have a look at the condition of them and also put an endoscope camera into the cylinders to see if they have been steam cleaned. (supposedly a sign of coolant leakage into cylinders)
I don’t have a coolant pressure tester but might be able to borrow one. There isn’t any coolant leaking onto the ground or the floor area near the heater core. I’ll also do the leak down test and the combustion leak test again using this tool.
It’s a real shame, the car was an ex wedding car and has had a lot of work spent on it including engine work. (reconditioned head ?)
I bought the car at auction. I’m sure the previous owner knew that the head gasket was leaking at it’s embryonic stage that’s why he put it up for auction.
The car has always ran rough since I’ve owned it. I drove it around for almost 3 years so at least i got to enjoy the car for that time. I REALLY love the car but there is no way that i can repair that engine. I might get lucky and find a used engine but i doubt it.
I’ll post all my findings when i get a chance to rerun all those previous tests I did.
Thanks again for the assistance
Hi Tony, thanks for the suggestion but i’ll just redo do the tests i did 6 months ago. Forty dollars isn’t much it’s just i’m curious as to where the differences are in comparison to the previous tests I did.
I suspect that the leak is in between the cylinders which means the cylinder compression tests won’t be 150 psi for all the cylinders like they were last time.
It’s a clear sign that water goes into your oil Nick.
Once the gasket starts to deteriorate it’s downhill from there…
If it was me, I would tend to replace the head gasket, then you will know that you have a reconditioned brand new head, rather than to do all this work to put in an engine that you will not know if it’s really good until it’s in.
My $2…
Best,
Aristides
Hi Aristides, thanks for your input but repairing the head gasket isn’t an option for me.
The engine has lower compression than it should have. When i checked the compression 6 months ago all 6 cylinders were around 150 psi. Being a high compression engine they should have around 175 psi per cylinder. This means it will also need piston rings replaced.
I don’t think whoever did the engine work previously did a good job or it wasn’t serviced properly by the previous owner.
I’ve been servicing it every 6 months/5000 kms and taking good care of it… This is the main reason the car has lasted 3 years as a daily driver.
I don’t regret buying it because it has allowed me to experience owning and driving my dream car for not a lot of money. All up i’ve probably spent a total of $5,000 on it so it’s not huge loss for the enjoyment its given me.
1 Like
**
In which case there will not case coolant leaks, Nick - it will show up as low compression on two adjacent cylinders…
Frank
xj6 85 Sov Europe (UK/NZ)
**
many years ago, had a S1 XJ6 that had that problem, 2 cyls had low pressure, sealed it with a product that was sold for that job (twice)…lasted about 6months each time on a daily driver…then I sold it (cheap)
Wish I had just replaced the head gasket, and kept it, was a sweet-looking SWB version
**
How/where was that product applied, Tony…?
Frank
xj6 85 Sov Europe (UK/NZ)
**