Hi I just replaced my XJ8 1998 expansion tank and am trying bleed the air from the cooling system.

The issue is if I stick a funnel into the expansion tank opening (tight fit) and fill the funnel with coolant it just drains straight out to the reservoir bottle down by the bottom of the radiator. ???

When I look at videos the coolant stays in the funnel/bottle and as the air bubbles work their way up then the coolant goes down into the cooling system.

What's causing the coolant to just flow straight out into the overflow bottle and how do I stop that please?

Greg - Australia

 

Did you criss-cross the two small coolant lines in the front of the tank? If not, you need to do so

 

As Quad said, you've got the coolant line mismatched, I did the same thing at one point haha, I've attached an image of the correct orientation.

 

perhaps you have bad cap

 

I had a new radiator installed (leaking at bottom from curb damage) . That showed up a fine crack in the expansion tank - so replaced the tank.

My coolant hose as per your image looks the same but hard to tell and it "seems" your higher connector has its thin hose running up out of sight (I assume coolant is entering from the radiator through this hose into the expansion tank ? - my tank has has a wider diameter hose that goes from that front upper connector on the tank straight to the top of the radiator - the coolant from the radiator enters the expansion tank (when the cap is off) through a hole close to the top of the opening and would be cut off when the cap is on. Is this connector and its entrance hole the right one for radiator connection or is the upper hole for the thin pipe to the over flow bottle (only being opened for access when the coolant system pressure allows the cap to open and expose this upper exit hole?

I can't really tell from your photo - which pipe connector on the front of your tank is going to the overflow bottle.? If you could confirm if its the upper connector (upper most entrance hole to tank) or the lower connector please?

Why is there this smaller hose going from the top of my radiator to my expansion bottle anyway? My other cars just have the two big diameter coolant hoses from their radiators to the engine - whereas I have both of those "and" this smaller one. When the cap is off and the car is running water flows strongly from this top small hose from the radiator into the expansion tank through the upper most connector/hole - you can see it clearly entering the thank "Above" the coolant level - dropping down into the tank.
Going back to your advice - please clarify which connector (upper or lower) connects to the over flow bottle (the hole above the coolant level in the tank or the lower one below the coolant level in the tank.

Thank you.

 

The connector positioned higher on the expansion tank should connect to the Overflow Bottle. As you observed, this port is "cut-off" when the cap is screwed on. The function of the Overflow Bottle is to catch any coolant that is, due to expansion, pushed pass the cap's pressure control valve. On engine cool-down, the vacuum in the cooling system created by the coolant "shrinkage" sucks the coolant from the Overflow Bottle, pass another "soft" check valve, back into the system.

The lower port on the expansion tank is connected to the top of the radiator to purge any air in the cooling system.

 

Perhaps if you posted a picture of your current hose orientation, we might be able to better advise on what's gone wrong.
The top connection should be the one that runs to the overflow tank.

 

Thanks for your suggestions. It looks like the hoses were back to front. Given I've never had to touch this part of the car over the years - I have to assume it was the radiator guy a week ago - although why he needed to touch them either is beyond me. Anyway fingers crossed.

 

I've just had the same issue after my [non-Jaguar] mechanic repaired a small leak in my radiator. I have a 2001 XJR.

My car seemed to be running hotter than normal and occasionally there were coolant spots. My mechanic checked 1) pressure tested and vacuum tested for leaks 2) visual inspection 3) head gasket checks 4) attempted to get the engine hot in order to find the "leak". He couldn't find anything, probably because he didn't get the car hot enough.

Recently, on a hot day, my car hit 104°C/219°F and a coolant low light appeared at the same time. I'm assuming that if the expansion tank lines (below) are not crossed, the cooling system wouldn't be maintaining pressure and would then overheat and lose coolant out of the overflow tank?

...so, how would my car maintain pressure/pass a pressure test if these hoses were not crossed?

 

The routing in your picture is incorrect. Swap them and you should be good

 

If it was not clear enough from previous posts, look at this picture: your hoses need to be swapped

 

Thanks, for confirming my mechanic attached the hoses incorrectly, these are now crossed.

I was also curious how my car would have passed a cooling system pressure test and vacuum test if these hoses were around the wrong way (given the overflow tank isn't pressurised).

 

Did you witness the cooling system pressure test performed by your mechanic?

 

Sorry for the delay in replying, it's been a hectic time for me!

I didn't witness the pressure test.

I swapped the hoses around to the correct positions and all seems to be working nicely. After a 5 hour drive in warmish temps (31*C/88F) my girl behaved nicely - touching 96*C/205*F once or twice (off the motorway or after a longish crawl upwards).

Now, a drive over the Blue Mountains on a hot Sydney day will be the real test!