Upon cooling down the upper right radiator hose collapses; gets sucked-in. This has been happening for at least five years over which I have replaced the "octopus", thermostat, thermostat housing, right upper radiator hose, plastic bleeder hose, expansion tank and cap (twice)....and the hose continues to get sucked-in.
The coolant level does go down over several months time, so of course there is a small leak somewhere.....that I just have not been able to find.

Asking for suggestions as to where I have not looked. Is the right upper radiator hose telling me something that I am not understanding?

Thanks,

 

If it collapses as it cools (and contracts), you could have a sticking thermostat or a blockage in the pipe from the Atmospheric Recovery Bottle (behind the RH front wheelarch liner) to Expansion Tank.

Graham

 

Doubt that the thermostat is sticking; coolant appears to warm-up normally...although all I have to go-by is the stupid coolant temp gauge....which I believe does indicate that the coolant temp does increase and gets to a point....then of course the stupid gauge needle moves no more.

I will have to take a look at the piping to the Atmospheric Recovery Bottle....have never seen the bottle itself. Probably should remove the inner wheel arch and see what condition it is in.

Thanks for the suggestion.....any others??

 

The radiator cap might need replacing.

 

The radiator cap..??....not following that. The radiator cap is supposed to seal and then vent when over pressure.....or am I missing something?

One other piece of info.....cold engine, coolant reservoir cap removed, squeezing the right upper radiator hose results in coolant coming out the top of the reservoir......so no blockage there....coolant is flowing.

I did try to push some air into the piping to the Atmospheric Recovery Bottle....seemed to be blocked....will need to look at this further.

 

I'm pretty sure the recovery bottle is in front of the Left wheel, and a blockage could be the problem , or too low fluid in the bottle, or a bad Rad cap.

 

+1 on the radiator cap. Happened to me at least once.
John

 

The reservoir cap not only allows fluid to move to the atmospheric tank, it allows the fluid to return to the system during cooldown. A malfunctioning cap could result i the pressure system being under vacuum after cooldown, hence collapsed hose.

 

Got it. Ordering a new cap.
Thanks guys.

 

A new coolant reservoir cap has solved this same problem for me .... twice. They seem to last maybe three years then need to be replaced....

 

Yep....I checked my service history, found that I had noted that a new reservoir cap solved the problem before. I purchased a Gates cap and it lasted about two years and then I needed to replace the reservoir itself which came with a new cap.
Ordered a URO cap this time....supposed to be here on Friday.

I am still going to check the Atmospheric Recovery Bottle and piping....on my list of things to do this week.

Sure appreciate the comments.

 

Found the Atmospheric Recovery Bottle this afternoon, not too exciting though. Had just a little bit of coolant in the bottle. Removed the piping, using my bicycle air pump blew air towards the expansion tank. I barely pushed down on the pump, there was a slight bit of hesitation and then the line cleared, spraying coolant all over the place. Exactly what I was trying to avoid.
But oh well, now I know it is clear. Waiting for the new expansion tank cap to arrive.

When I removed the right front tire, I had a quite unpleasant surprise. Get to get new front tires....see my new posting under alignment issues.

 

Do not rely on the instrument cluster gauge to indicate the current temperature of the coolant. The needle does not move from the middle position between 96 C and 129 C, which by then may be too late to avoid an overheating situation.

Use a smartphone with the Torque app to accurately monitor the coolant temperature via the OBD port with a Bluetooth interface.

 

Correct....after the coolant temp reaches a certain temp, the gauge needle goes to the middle and stays there. I should have installed the real gauges when I was going to....but at that time did not think we would be keeping the XK8 much longer.
The new expansion tank cap has arrived. Going to be another few days as awaiting upper shock mounts from Welsh to arrive.

 

Let us know if the new coolant reservoir cap indeed solves that issue....

 

New coolant reservoir cap is installed, just have not started engine or driven car in two months.....but next week....going in for an alignment, will update afterwards.

 

Had to wash the XK8 this morning....two months of dust on it from garage.....so let engine run for about 10min, shut off and no collapsed upper radiator hose; the new coolant reservoir cap fixed it....again.

Next time I place a RockAuto order, will get a spare cap to have at the ready....since these only last a few years.

Thanks for the help.

 

I installed my fourth new coolant reservoir cap yesterday morning. This time I opted for one of the $10-with-free-shipping Chinese ones. We shall see how long it lasts. I still have the last OEM cap I ordered in February 2015 as well as the aftermarket cap that came with the aftermarket coolant reservoir tank I installed in September 2017. The aftermarket cap never fit very well, and the OEM cap still functioned but was getting difficult to unscrew because it was beginning to fail. They can serve as my back-up plan if this cheap Chinese cap only lasts a short time....

 

Bringing this up again....same problem. Installed a new STANT reservoir cap, drove car.....same problem. When engine is almost cool again, right radiator hose is sucked-in just before the 90° turn into the thermostat housing.

I put the older URO cap back on.

At a loss now.....is it time to replace the reservoir again?

 

I would try another coolant expansion tank cap. These things just do not last very long and I would not be surprised if quite a few of the new ones are defective right off the assembly line. Keep in mind that we are dealing with Chinese plastic parts nowadays....