"8. Put the transmision on drive, parking break on, and accelerated the engine to about 1,500 rpm with the break on. After a couple of minutes coolant started to drip on the floor from the resevoir on the front driver side."

That procedure you are doing is called a stall test. Without making a long post about it, it's a transmission test. It's also not recommended to perform more than 10 seconds because it's maximum stress on the engine and mostly transmission. The transmission fluid temperature goes thru the roof when performed much more than the recommended 10 or so seconds. The correlation between engine and transmission that you asked is that on your driver side (US car) of the radiator is an internal transmission oil cooler. See where I'm going with this? So the stall test that you perform for minutes at a time substantially raises the temperature of the transmission fluid and the heat is dissipated via thru the transmission oil cooler that's built into your radiator. You are making the car overheat doing the stall test.

If you let the car idle for 30 minutes in park and it doesn't overheat, go out and drive the car and continue to monitor the coolant temps after your repair. If you find the engine going above 98°C , turn your heater on full hot with fan on high and make sure the A/C is off so you can make it home without potential of engine failure.

 

I will inspect the secondary tank for cracks.
The only reason for step 8 is that everytime I think the car is ok, it overheat away from the shop and it takes me forever to get back, so I am triying to replicate driving load.

I spoke to the previous owner and he told me a couple of stories about overheating incidents to help with the investigation.

He told me that sometimes he could drive the car for a week with no problem, and then all of the sudden it will start to overheat again.

One time it started to overheat close to his house and when he was about to stop to let it cool down, the temperature started droping fast by itself.

That same time it gave him a transmision overheat message, and all sort of problems started with the transmision from that point on. We changed the connector plate with a defective speed sensor and all is back to normal with the transmision.

After inspecting the old connector plate I saw that the plastic around the speed sensor was cracked, it seem that the high temps cracked the plastic on the connector plate.

So what could be the reasons for a transmision to everheat? Not enough fluid? We used the MB/Chrysler transmision dip stick. The transmision is working fine and smooth since the connector plate change.

Any more ideas or suggestions before I take the whole cooling system appart?

 

Il guess that it is not that many things that could cause an automatic transmission to overheat.
What comes to my mind first is either a clutch or a brakeband that slips.. its not the converter that stalls... it slips inside... then i can imagen that things get superhot in an instant.. just like a wheelbrake or a slipping clutch.. hmm..

 

Took a test drive this morning with the scanner attached.

More weird information.

If the car is in Park or Neutral the transmission temperature reading is the same as the engine temperature.

When I shift the car in gear or reverse, it reads a lower temperare???

For example P or N = temp 147 degrees F
D or R = temp 230 degrees F

Again, on middle on Park will not overheat!

 

Today was a busy day and lots of data collected, and tests performed.

First I took out thermostat and water pump for inspection, they looked to be in working order and the blades of the pump were ok, but replaced the water pump anyway, I am still waiting for the thermostat, but it also looked fine and properly installed.

Then we tested compresion on all cylinders and all (8)were in the 150psi range, also inspected with a camera inside the chambers and pistons looked good, and sparkplugs also looked ok. No sign of water inside the cylinders.

The hardest test was the cooling system pressure test. In order to test the system it was a pain to get an attachement for the coolant resevoir that did not leaked (we ended up adding some o-rings to get it to seal. The other pain was how to seal the hose that goes to the overflow tank. But once we were set and sealed the resevoir we pumped the system to 15psi and started to loose pressure. Slow but steady, aha a cooling system leak!!..

We found it and it was one of the thermoplatic hoses that go from the resevoir to the SC upper housing that was missing one of the (2) o-rings at the connection fitting and the second one disintegrated while replacing it. We changed both o-rings and we were holding 15psi. With no loss.

Tomorrow before putting all back together we will air test each cylinder chamber. We will place the piston at the bottom of the chamber, and apply about 90psi of air while holding the crank in place. This way we can rule out head gasket failure completely.

We will see, i will keep you posted of tomorrow's test and test drive.

 

Still overheating!!!!!

Since we were getting 150 psi on all cylinder, no bubbles on coolant, no exhaust smoke, a blown head gasket does not make sence. Or is it still a possibility?

The cooling system is holding pressure at 15 psi. At is purged using the supercharger electrical pump.

Next my only guess left are:

1. Clogged catalytic converters?
2. Lean fuel condition?
3. Bad Timing or advance timing?

I was measuring the temperature on idle with the scanner and the temperature rises up to 222 to 225 that i think is hot, even though the needle reads normal.

I do not have to accelerate the car too much or for too long before the temp goes to 240 and then I need to stop to let it cool down.

Once the temperature raises to 240 it starts to drip coolant from the underside reservoir overflow tank side port.

Any ideas? or other things to check? Based on past problems or experience?

Thanks
Ivan

 

This sounds more like a cracked head or partially blocked crossover passage for the heads or bad temp sensor. The temp sensor and thermostat work in combination to determine when and if the thermostat should open. Usually when a temp sensor goes bad it will throw a code. Being that this is happening without throwing that code I would expect to find something mechanical rather than electrical. Sitting in park or neutral does not put a load on the motor. Once the transmission is engaged, even at idle there is a load on the motor. This is why if you have a water passage that is partially blocked or has a crack in it you will see the rapid temp rise, then when taking the load off the motor, getting the temp to drop. I could be all wet but just throwing theories out for ya

 

With all that you have done, my conclusion is that the head gaskets don't seal when under a load. If you replace the head gaskets with the 4.2 MLS ones, the problem will go away.

 

I removed the catalytics today, and still overheated.

We will start to remove the heads. Once out i will problably take them to the machine shop to be rectified.

I am not familiar with the 4.2 MLS gaskets, what are those a who sells them. Isn't the 4.2 an online 6cly. Engine?? I will like to do also the valve cover gaskets.

Any other while there recomendation of things to look for and replace besides hoses under the intake?

My only doubt at this point is how we are getting 150psi compresion on all cylinders and have a blown head gasket? They are coming out anyway, but what can be a logical explination for this?

 

I dont know if this applies really.. but.. if you have a dodgy headgasget.. and if.. water gets in to the cylinder... that cylinder would be clean as a whistle inside.. including the sparkplug.. maybe if you have a look inside cylinders with a boroscope... just thinking..


An egnine overheating.. ie. it can not get rid of the heat accumulated in the water efficient enough.. i mean.. normally you should be able floor it uphill with cupe and trunk filled to the brim.. without the engine breaking a sweat.. there cannot be that many reasons..


Its going to be really interresting to learn what the root cause is in this case..


hmm..

 

2006 Range Rover 4.2 cylinder head gaskets and 20 head bolts are what you want to buy. These are the exact same as a 2004 XJ 4.2 V8 but cost more because of the 'Jaguar' name I suppose. I have done probably a dozen cars with the MLS head gaskets and not one has had an issue with these gaskets. When you do the valve cover gaskets, make absolutely sure you get 28 new bolt seals. These are the key to prevent oil leaks.

 

Is this engine the same as the one on my 1999?

ENGINE 4.0L XJR SUPERCHARGED OPTION VIN 8 7TH DIGIT FITS 98 XJ8 770497 | eBay

What years are compatible with an 99?
Vin number: SAJPX1841XC861012

Any other good source for these engines besides Ebay?

 

that should be the same engine yes. Make sure of the mileage and that it has never been overheated lol. Other thing to make sure of is the supercharger has not been beat. You can check with Jaguar Heaven to see what they have or call LKQ engines.

 

You could also look here-
Car-Part.com--Used Auto Parts Market

There's one in MA with 55k on the clock
The direct link
http://www.nationwideautorecycling.c...1#.WR4eYpLyttQ

 

Before buying a replacement engine order and fit an OEM thermostat.
Have you carried out a sniff test on the coolant?
A faulty header tank cap can lead to overheating.
Do the fans chime in when it gets hot, I mean both running fast after the engine is shut off?

 

I have replaced thermostat and water pump.

I am removing the heads next week, but so far we have done the following test:

Compression test cold engine: Result a healthy 150psi per cylinder

Chemical test on the cooling system: The fluid stays blue (no gases)

Pressure tested the cooling system: holds 15 psi steady.

Connected the cooling system gage and started the engine: pressure stayed around 9-10 psi. Took the car for a short drive with the gauge on, pressure quickly increase to 15-16psi and has to stop the car.

I tried a head gasket sealer to see if there was some improvement, and it made no difference.

The car does not smoke thru the tail pipe
The coolant has no sign of oil
The oil has no sign of coolant
There are no codes on the ECM
Both fans are working (high and low speed).

I ordered the head gaskets, but it does not make any sense.

My only confirmation is this other member, that did not do this many tests and had a similar problem.

https://www.jaguarforums.com/forum/x...ase-he-172768/

As of now, I am waiting on the parts to start disassembly. Unless someone has another test (that I can pass!) and still have a head gasket problem.

 

sounds more and more like a cracked head to be honest. Before ordering a whole new engine, have the heads checked at a good machine shop. Cheap machine shops = poor work.

 

Thanks again for all the help. I will post some pictures once I have the heads out next week.

 

Ok, heads are out, here are the pictures, opinions from the experts, please!

 

Looks like the heads are probably warped which is to be expected after overheating. More than likely it's an internal crack in the heads since they usually warp after overheating, then blow the head gasket between cylinders or wherever the weak point of the gasket is.