I have a 98 V70 261k miles.

I have been having a coolant leak out of the expansion tank hose at the thermostat housing and out of the hose connection on the tank.

My question is, under normal conditions should the top radiator hose(radiator to thermostat) become hard to squeeze once the engine is warmed up?

The expansion tank is filled to the proper level and once warm the level increases in the tank to well above max.

First thought was the thermostat was bad and stuck closed but drove it this morning and gauge reads normal but hose was still hard.

Seems like there is unusually high pressure forcing it to leak out of the expansion tank hose.

I got a new cap and expansion tank hose. I don't think that this was the issue as I still had fluid pooling around the cap.

When I went to change the expansion tank hose O loosened the radiator cap to relieve the pressure. When I took the expansion tank hose off of the thermostat housing fluid kept coming up out of the nipple.

Car was cool (hadn't been run for 3 or 4 hours. Where is the pressure coming form that would force the fluid up out of the thermostat hosing nipple? particularly after I vented the system at the cap.

The top hose is full of fluid and that is above the expansion tank hose. When you pulled off the new cap, did pressure escape?

Lets hope that there isn't a blockage in the radiator. Checking the bottom hose for heat isn't easy with the air guide under the radiator area. Of course, if the radiator is partially blocked, your temperature should rise steadily. You would be the first with a blocked radiator.
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My name is Klaus and I am a V♂lv♂holic

Yes pressure released when I opened the radiator cap.(even after it had set for several hours.
I'll see if i can check the lower rad hose tomorrow but the temp is holding steady at normal.

Still seems like a possible blown head gasket but I am not getting bubbles , cylinders aren't clean and compression was decent.

had a chance to drive the car a bit today and the fluid level does rise in the expansion tank after 15 minutes or so of driving.

this is a sign of a bad head gasket form what I have researched but is it definite or can the fluid level rise under normal conditions?

Ok so when my daughter brought the car home I removed the radiator cap to look for bubbles while it was running.

Didn't see any bubbles, should they be coming form the hose in the bottom of the expansion tank or the vent hose?

Pulled the plugs all pistons look the same carbon on top.

Checked compression while I had the plugs out
1-160, 2-155, 3-160, 4-155, 5-165

This is lower than what my hanes book says it should be but they are all pretty close and it was a harbor freight gauge. I also did hold the throttle open while doing the test.

I moved the clamps on the expansion tank hose to a fresh location to see if the hose was fatigued in that area so we'll see if it makes any difference tomorrow.

The compression reading is normal for a cold engine. The engine should always be 'warm' when checking compression, the engine oil will then coat the rings.

The bubbles will show up when the thermostat opens, they will come up from the bottom of the expansion tank - the hose that sometimes leaks(?). I suggest replacing that hose rather than moving the clamps. Also, replace the cap as it is a cheap thing to do.
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My name is Klaus and I am a V♂lv♂holic

No, the upper hose should never get hard and the coolant tank level should go down not up when the thermostat opens. You have a leaking head gasket which can be fatal if a hose ruptures.

Pull all 5 spark plugs and shine a small flashlight down the plug hole. A leaking cylinder will be nice and clean compared to the normal carbon deposits.


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My name is Klaus and I am a V♂lv♂holic

This can be a sign of hot exhaust gasses in the cylinder leaking past the cylinder head gasket and into the engine cooling passages. The internal cooling system pressure becomes abnormally high, hoses bulging and excess pressure is released through the pressure cap and/or coolant hose leaks. I lived this exact scenario with a 240 turbo. The fix is to replace the cylinder head gasket and while disassembled, insure there are no cracks in the cylinder head.

Find a reputable repair shop that has the instrument to detect exhaust gas hydrocarbons in the cooling system. The answer will help your troubleshooting.

Just curious with this scenario would I also see water in the oil?

If the head gasket is leaking cylinder pressure into the cooling system you will see bubbles in the expansion tank when the engine is warm and running. Since the pressure cap is on the expansion tank you will need to start the car with it removed or be very careful removing it when hot (a good way to get a scalded hand...).

Also, if the head gasket is leaking between the cylinder and the cooling system you will see that one or more spark plugs is very clean, maybe with a slight green tint on the porcelain.

Greg

Sometimes yes, sometimes no. Depends if the head gasket leakage is also allowing coolant into the oil passageways. Have seen both. On the 240 turbo, the head gasket failure was limited to leaking exhaust gas into coolant, and not coolant into oil lubrication system.