Hi,

I just recently bought a BMW X5 2005. Checked out the car properly. Everything seemed fair and well. Impressively pulled through all the tests we put it through etc nothing came uo worth querying. Driven the car over 140 miles back home on the same day and around 30 miles the next day too. However on the 3rd day I noticed engine overheating. Temp gauge was normal. I noticed that it took a lot of time for the car to cool down when the engine was warm.

Alarms bell rang at this time, however there was nothing on the dashboard to show anything was wrong. Waited a few hours and car was cool. Took it out for a short drive and after a few minutes the engine management light came up, shortly followed by the yellow explaination mark on the left hand size of the dashboard (this is not the tyre explaination mark though). I also noticed the temp gauge playing up. The car clonked out a few times.

I pulled up in safe place and called AA. Technician came and checked everything out. Did a few tests nothing showed up positive. Previous owner told me that the expansion tank was changed recently as previous one popped.

There was a lot of air lock / pressure in the coolant system. Heating was working fine. There is no mix of oil and water in the coolant system. All the other tests proved negative too. No milky/cloudy substance in oil. No white smoke. No obvious signs of head gasket failure.

However ... the air lock in the coolant system is coming from somewhere. Can anyone advise further?

Baz

Hi Baz

What engine ? 3.0, 4.4, 4.6, 4.8 or 3.0 diesel. A garage can do a sniff test on the header tank which will tell you straight away if there is a gasket issue (not unheard of but quite rare). Was the purchase from a garage or private? If a sniff test confirms gasket failure then I would  ask the seller for some support, difficult situation as it will be difficult to prove it was an existing condition.

I would check the thermostat and water pump if its is failed or thermostat failed closed then that will pressurize the header tank (not good when it's plastic) Check the colour of the coolant it should be changed every few years as part of the maintenance. 

Hope this helps

Dave

Hi Baz....welcome to the Club

I would agree with Greydog on everything he has mentioned and also sometimes it can be something as simple as the coolant pressure cap because if this is problematic then it can either not blow....hence the reservoir popping and not the cap releasing the pressure and also if it is weak, this can introduce a lower boiling point.

So for the case of either pressure testing it or even replacing it, it would be worth looking at before spending big money. Also the sniffer test for combustion gas in the coolant is definitely a must as also a cheap diagnostic test.

Temperature Infra-Red gun would determine where the hotspots are in the engine and show coolant circulation temperatures.

Let us know how you get on with it

Cheers,   Trevor

Hello. The AA technician that came out said the water pump is running fine, and other parts are running fine. He put it down to either a hole elsewhere allowing air to come into the system or possible headgasket failure ...

 

He did a tempreture test on the pipe with a lazer temp checker and it seemed ok he said.

However at this moment is time there is no mayo on engine oil cap, the oil looks fresh. The high tempreture doesnt always show up on the dashboard, it seems like its normal operating temp but engine management light is on and you can feel the heat around the cars emgine bay. 

Also the blue liquid test has been done too and has come negative. Liquid remained blue.

 

Heating system fully works.

 

Car doesn't jerk, starts and drives as normal.

Which engine do you have ? 3.0 petrol 4.4 V8 4.8 V8 or 3.0 Diesel

The X5 has more than 1 temp sender 1 at the thermostat on in the lower water pipe the Engine Management uses an average of the 2 that is why the needle sits in the middle most of the time. My money would still be on one of the thermostats being stuck closed and restricting circulation, beware as the rad and the header tank have plastic parts and once split will have to be replaced not repaired. Water pumps also have been known to loose the impeller so externally look fine but actually move very little water. As your EML has been triggered I would have thought a fault code would be logged so getting codes read will help in diagnosis. 

If your car is a 6 cylinder Petrol or Diesel you have 2 Thermostats 1 at the water pump and 1 at the bottom hose connection under the header tank if either is in a failed condition you will have a problem if both have failed a big problem.

If your car is a V8 you again have 2 thermostats in the system plus a temperature sensor in the lower main hose.

On 05/09/2017 at 5:29 PM, Greydog said:

Which engine do you have ? 3.0 petrol 4.4 V8 4.8 V8 or 3.0 Diesel

The X5 has more than 1 temp sender 1 at the thermostat on in the lower water pipe the Engine Management uses an average of the 2 that is why the needle sits in the middle most of the time. My money would still be on one of the thermostats being stuck closed and restricting circulation, beware as the rad and the header tank have plastic parts and once split will have to be replaced not repaired. Water pumps also have been known to loose the impeller so externally look fine but actually move very little water. As your EML has been triggered I would have thought a fault code would be logged so getting codes read will help in diagnosis. 

If your car is a 6 cylinder Petrol or Diesel you have 2 Thermostats 1 at the water pump and 1 at the bottom hose connection under the header tank if either is in a failed condition you will have a problem if both have failed a big problem.

If your car is a V8 you again have 2 thermostats in the system plus a temperature sensor in the lower main hose.

Hi, ours is 3.0i Sports 2005 E53. 

6 cylinder.

As I said earlier the 3.0i 6 cylinder engine has 2 thermostats it also has a temp sender in one of the hoses and I believe (but could be wrong) one in the cylinder head. 

These drawings and Part No's may help you see where they are. If you are sure there is no contamination in the coolant then I would change both thermostats as a precaution. 

If your EML is still on then I would say you need the codes read by a BMW specialist or a Garage with Autologic software to see what the issue is.

3.0 i Petrol Water pump.pdf

Rad Header Tank.pdf