The gift that keeps on giving - mystery coolant leak

[Howski]

It seems whenever you get a handle on a Rover something new pops up but I should know this by now. A little background on my Rover - 02' DII with 155k miles. I am running an inline 180 degree thermostat. Headgaskets done 30k ago. Expansion tank cap replaced a few months back. No signs of coolant in the oil. Do have an intermittent tick when warm which I haven't been able to is a larger exhaust leak (all manifold and downpipe nuts/bolts are tight) or possible slipped liner. No burning coolant smells. No coolant smell or smoke out the exhaust. Have been chasing a few minor coolant leaks over the past few months including the throttle body heater plate to some hose clamps that needed adjusting.

After a trip to the mountains last weekend I noticed the 'water rushing' noise behind the dash which I knew was air in the system. I had been tracking temps via my OBD dongle (this thing has been a great investment) and they never gotten above 190 during this period so that's some solace. The coolant was low with no obvious puddles or leaks at the time. I topped up, bled and resumed driving on Monday. When I did wake up Monday there was a dried area on the ground but I wasn't able to determine it was coolant. Took a 20 mile drive last night, showing no leaks and the coolant level was about where it should be during operation and when I returned home.. I woke up to a puddle in the driveway this morning, however I was able to determine it was coolant. It is located on the passenger side, between the tire and engine block.Does not seem to be coming from the expansion tank overflow tube. A quick look at hoses didn't seem to yield any obvious leaks either. There has been zero burning coolant smell throughout this ordeal. I'll slide under and have a look tonight but wanted to get initial thoughts - the fact it seems to be leaking after shutdown is a little odd to me. Any initial thoughts or suggestions would be appreciated

 

[adriatic04]

do you have hot air blowing through the vents? sounds like a heater core leak.

 

[Howski]

do you have hot air blowing through the vents? sounds like a heater core leak.

Yes, heat blow hot air per usual. Would also add that the carpet is not wet at all on the passenger floor board

 

[kcabpilot]

My guess is cracked expansion tank, specifically at the small nipple on the bottom for the return line from the throttle body heater. It suffers abuse as the tank is removed and re-installed.

 

[Howski]

Thank you for that tip. Had that happen on my old D2 (which resulted in complete failure), I should've thought of it. Will examine the expansion tank and connections this evening. That is definitely the general are

 

[Howski]

On a quick glance during my lunch hour the expansion tank (unfortunately) didn't appear to the culprit. No dampness or coolant present around connections or underneath the tank. I will follow up on that also after I can take it on another extended drive and get some proper heat into it - that seems to be when the leak presents itself.

Any reasonable possibility this could freeze plugs? Just looking for a list of things to check

 

[JohnB]

Borrow a coolant pressure tester. Only way to find leaks.

 

[kade]

My guess is cracked expansion tank, specifically at the small nipple on the bottom for the return line from the throttle body heater. It suffers abuse as the tank is removed and re-installed.

I had this as well. Even though you have had it happen before, check it while it's hot after shutoff. That is the only time mine would leak before I swapped it out. I have a spare if you need it.

 

[ozscott]

Mate check also radiator tank on that side to see if it's leaking. Check also coolant return hose between expansion tank and top of radiator side tank. You may have already replaced (with something like 5/16th Dayco heater hose).

Cheers

 

[number9]

A quick look at hoses didn't seem to yield any obvious leaks either.

You probably need to get dirty beneath the D2 using a good flashlight and mirror. Remove the underbelly panel if still installed to get better access for your visual inspection. Many engines need to be cleaned up a bit to find mystery leaks.
......

 

[Howski]

I haven't used the heater today and noticed no coolant loss on several shorter trips. I used the heater both times it has lost coolant. Is there anything on the coolant system that would involve the heater? It's my understanding coolant flows through the heater core constantly on a D2, unlike some vehicles - is this correct?

 

[Howski]

Sometimes you answer your own questions - the leak was at the firewall where the heater hose attaches to the heater core. Never smelled coolant as it would go down the firewall and behind the cat heat shield. An adjusted hose clamp and I'm on my way again