Ok, so I am going to quickly give you the down low on my position. First of all, I have a 1999 red jaguar xk8 with 103,411 miles. All stock and in very very clean and good shape. No problems ever! When I converted my plastic coolant sensor holder area to aluminum, I replaced all my hoses, around 25K miles ago. no worries, no problems. I did not know of the hose at the bottom of the engine. Yesterday it was 90 degrees in Southern California I am driving on the freeway and my check coolant level came on the dashboard. I immediately pulled off the freeway and checked it out. It was bone dry. No steam from the engine, no signs of overheating. I put coolant back into it and checked everything out and was on my way. I knew coolant had to be going somewhere so I was concerned for a head gasket issue and that maybe coolant was getting into the engine. But, I was not sure at this point. The car started right back. up and I went on my way. five miles down the road, the coolant light came back on. I pull over again, but this time behind me I could see a line of coolant dashing out under neath the car. I thought, Oh ****!

I pulled over and again, bone dry. I kept the car off and immediately called AAA for a tow to the nearest auto mechanic. This am, I got a call from the auto shop telling me that they cannot service my car, but for free he assessed it to say that the engine was locked. that water and mixed with the oil and the engine had locked. So, I am not stupid but, I was very perplexed because the coolant sensor never said the car overheated. also, the tow truck drove the car onto the flat bed truck. the engine was still starting so how can it be locked if it starts? so if it was a leak that caused the coolant to go dry, then what it overheated and then the coolant mixed with the oil? I am confused cause this doesn't make sense to me. Can someone make sense of this, I am frustrated beyond expression in that I preventably put this money into this car to do all this stuff to keep this from happening and it still happened. so I should have just Ran with the plastic parts and the bad hoses if the engine was going to overheat anyways. why did my car coolant temperature sensor that was as new as a few months ago, why did it show middle ways on heat and not high in the danger zone? So what the temperature sensor does not work on these cars? I am so upset, I loved my car and now she has been taken away from me and I did not even get to say good bye. Any thoughts please?

 

Welcome to the forum - plenty of information and people here to help guide you. As this is your first post - please stop by the New Member section to post an intro. In return, you wil receive a warm welcome and useful tips to navigate your way through the forum sections.

https://www.jaguarforums.com/forum/n...-intro-must-5/

The temp sensor/temp indicator does work but it does not go out of the normal band to warn you of overheating until you are well into the danger zone. It is best to either install the Real Gauge mod (created by forum member JagWrangler) or use a Bluetooth code reader coupled with the Torque Pro app to constantly monitor temperature.

Get a cost to rebuild and compare to cost for replacement. You could also look at an LS1 conversion. Parting out could take months

 

Troy,

Sorry to hear about your cooked engine. But chill, it's all fixable and it's only money.

From your description, when you first had the problem, did you just put coolant back into the expansion tank, or did you have the engine running and filled it continually with coolant? From the sounds of things, you haven't run the car HOT for long enough to cause massive damage to the aluminium block so it should be a regular garage engine tear down. These V8 engines are fairly common so shop around for quotations for the engine rebuild.

In case you didn't know, the temp. and oil gauges are "Dumb Switches" and don't display real data. The dial stays in the middle until it reaches a predetermined danger limit then the dial moves. Many Forum members install the "Real Gauge" mod or use the OBD2 port with an active reader on the dash to get real data.

It's always better to repair what you have, if possible, as you know it'll fit. Buying a re-conditioned engine seems to always come with other little fit up problems despite best efforts.

Parting out the car may give you some cash, to soothe your pain, but it's long winded process, takes ages, and buyers only want specific bits. Your car sounds "....very clean and in good shape..." so it would be a shame to dismantle it and then have to see the diminishing skeleton in your garage for months.

Selling it, in the non running state, won't be worth much, but the funds could go into buying a new one. That'll be fun. Prices are down so you'll get a bargain. Go for the later XKR with the better 4.2L engine and the ZF6 gearbox. Same car, more powerful, more reliable and had better options. That should put a smile on your face again.

 

At this point, you probably need a more solid diagnostic. If you have coolant in the engine oil, it is likely there is a failed head gasket. The engine being locked could be hydro-lock (cylinder full of coolant). Maybe consider pulling the spark plugs, check if the engine still rotates and do a compression test. Maybe a visual inspection with a small camera. On a failed head gasket, you can have compression pressure making in in the cooling system and flushing out the coolant into the overflow bottle in the wheel well and then on to the pavement below. These tests should not be crazy expensive to do and at least give you enough information to move forward. Best case, it is a head gasket job on one bank.

Best of luck, keep us posted.

 

There is a failure mode when there is a rapid loss of coolant that works as follows:

If there is a major (fast) cooling system leak due to hose separation, major plastic crack or large hose rip, the coolant level drops rapidly and ends up BELOW the coolant temperature sensor. The temperature sensor ends up sitting in air instead of coolant. It therefore never registers the overheating event through the threshold filters in the gauge computer.

Moral: If you get a low coolant warning, stop and check it immediately. If the reservoir is completely empty (not just low). DO NOT DRIVE any further, get a tow. Use of RealGauge or a real time OBD2 reader can also help because you will get used to what temperatures are normal for different conditions and you will probably see odd temperature behavior before the engine is damaged.

 

I bought an Autool X50 and mounted it on the dashboard to show engine temperature along with over temp alarm), battery voltage, and speed in KPH. It is plug and play and costs around €30.



More info in this thread.

https://www.jaguarforums.com/forum/x...-gauge-210411/

 

This is right on the money. Never ignore a low coolant warning, you could be riding to work on a scooter.