Came outside to check the coolant levels before heading on a trip and noticed the top radiator coolant hose almost collapsed under vacuum. Opening the expansion tank relieved the pressure.

 

Air in the coolant system? bad coolant pressure cap? blockage in the smaller run off hose to the coolant reservoir?

 

+1 and the fact you are using a garbage URO Parts hose!!!

UROParts, the mistake you only make once.

 

My experience with other vehicles that I have owned (I have never had this happen with my D2) It is typically the radiator cap or in our case the coolant overflow as mentioned already. I cant comment on the URO part because I have one too

 

URO = So bad even BritPart rejected it.

When I broke down on the road to Romp two years ago, the shop that fixed it up used World Pac to get the parts and while I was thankful they could get me back on the road with only 6 hours lost. The URO parts didn't last a year before they were garbage.

 

Oh dang. Had no idea about URO struggles. I guess I get to replace hoses again.

 

Just ordered all new LR hoses to replace the UROs. Noted for next time.

 

Can concur on the URO parts. They're notorious in the Mercedes/BMW community for disintegrating rubber components. If you're in a pinch and have no other option they'll get you home but definitely don't rely on them long-term.

 

Did you order a reservoir cap also?

 

I did indeed. That was also URO. Such shame.