Cooling system clogged?

[hiroku]

Today, I found that the radiator started leaking on my 2001 V70 T5. It's wet at the junction where the right endtank meets the central core.

Oddly enough, it only seems to drip when it's cooling down after a drive? When the engine is running or when the car sits overnight, everything stays dry and the level in the reservoir stays the same.
Anyone seen this behavior before?

This is the second coolant leak in the last 500 miles, since I flushed all of the gunk out of the system from a failed oil cooler. Last month I replaced the inlet heater core hose, which burst catastrophically.

Could it be an clog in the system? I noticed the bottom radiator hose is very hard when the engine is on, even if the thermostat is still closed.
Isn't the expansion tank cap supposed to vent excess pressure?

Did a couple of test drives while monitoring the actual coolant temperatures and everything behaves as it should with no signs of overheating. Thermostat seems to open when it should, cooling fan cycles at exactly 106 degrees Celsius, heater blows warm air, no temperature gradient across the radiator.
Should also mention I flushed the system with a cleaner product and ran a garden hose through it for almost an hour through the heater hoses, the thermostat housing, the expansion tank, and the top radiator hose until the water came out the bottom so clean you could drink it. No sign of any oil or dirt in the coolant in the expansion tank, it looks very clean.

I have commissioned a CO2 test of the cooling system and a compression test, but I don't think I'll find anything there. Looking for advice if there's anything else I can do other than replacing the radiator and doing another flush, just to have another new leak within a week.

Thanks.

[cn90]

I'd replace the radiator.
Choices are Volvo, Nissens.

[hiroku]

Appreciate the reply.

Replacing the radiator is a given I'm afraid - if it's leaking it's leaking, even if the conditions are a bit strange.
I'm more concerned about whether there is an underlying issue that needs to be addressed as well, considering it's the second leak in the space of a month.

Always a chance of old components reaching the end of their life at the same time, but the pressure in the lower radiator hose in particular is a bit concerning to me. I don't want to end up replacing the new radiator/hoses again next month.

[kcodyjr]

Oddly enough, it only seems to drip when it's cooling down after a drive? When the engine is running or when the car sits overnight, everything stays dry and the level in the reservoir stays the same.
Anyone seen this behavior before?

This is the second coolant leak in the last 500 miles, since I flushed all of the gunk out of the system from a failed oil cooler. Last month I replaced the inlet heater core hose, which burst catastrophically.

Could it be an clog in the system? I noticed the bottom radiator hose is very hard when the engine is on, even if the thermostat is still closed.
Isn't the expansion tank cap supposed to vent excess pressure?

In most cars, the lower radiator hose is the return. Pressure from the water pump comes through the top hose, after passing through the thermostat.

I'm just throwing stuff at the wall to see what sticks, but, it sounds like there might be some crap floating around near the inlet to the water pump. When it's running, it gets kicked up and water gets past it. When the engine stops, it settles in place and blocks the pump. Between that, and the thermostat closing, there's your unvented pressure in the radiator.

Engine and coolant temps do RISE after shutting the car off, while excess heat in the block bleeds into the unmoving coolant.

Have you done the water pump?

[hiroku]

Oddly enough, it only seems to drip when it's cooling down after a drive? When the engine is running or when the car sits overnight, everything stays dry and the level in the reservoir stays the same.
Anyone seen this behavior before?

This is the second coolant leak in the last 500 miles, since I flushed all of the gunk out of the system from a failed oil cooler. Last month I replaced the inlet heater core hose, which burst catastrophically.

Could it be an clog in the system? I noticed the bottom radiator hose is very hard when the engine is on, even if the thermostat is still closed.
Isn't the expansion tank cap supposed to vent excess pressure?

In most cars, the lower radiator hose is the return. Pressure from the water pump comes through the top hose, after passing through the thermostat.

I'm just throwing stuff at the wall to see what sticks, but, it sounds like there might be some crap floating around near the inlet to the water pump. When it's running, it gets kicked up and water gets past it. When the engine stops, it settles in place and blocks the pump. Between that, and the thermostat closing, there's your unvented pressure in the radiator.

Engine and coolant temps do RISE after shutting the car off, while excess heat in the block bleeds into the unmoving coolant.

Have you done the water pump?

That is pretty much my reasoning too.
Hopefully another flush will take care of that...

I haven't touched the timing belt and pump yet - have had the car for about two months now and that's currently in the low priority to-do list. But it will definitely get done at some point in the future.

[kcodyjr]

I haven't touched the timing belt and pump yet - have had the car for about two months now and that's currently in the low priority to-do list. But it will definitely get done at some point in the future.

You're having strange cooling issues. The pump, and the piping near it, is the next thing I'd look at. While doing the radiator. Since you'll have it open for the pump, do the crank and cam seals too if there's even the slightest oil dripping from them.

I would do the kind of flush where you put something into it and run it, to scrub out the insides, before taking it apart. With the thermostat removed.

[hiroku]

You're having strange cooling issues. The pump, and the piping near it, is the next thing I'd look at. While doing the radiator. Since you'll have it open for the pump, do the crank and cam seals too if there's even the slightest oil dripping from them.

I would do the kind of flush where you put something into it and run it, to scrub out the insides, before taking it apart. With the thermostat removed.

You mean the metal pipe that goes around the engine? I am considering replacing it, considering the levels of rust I have found in it - see below.

As for the flush, I dumped the cleaning product into the reservoir, drove for around 30 minutes, dumped out the gunk, waited for it to cool, then ran water from a garden hose through everythjng I could disconnect: heater hoses, thermostat housing (still the old design), radiator hoses, and expansion tank.
Only stopped when the water came out crystal clear about an hour later. This system had unseen levels of crap (curse people running tap water for years), but I'm still disappointed that something was left behind go clog stuff.

[kcodyjr]

Yeah, replace what you can see is rusted.

Did you open the drain on the block, remove the thermostat and reassemble the housing, then force water through the engine while it's free-flowing? If not, you may have cleaned everything BUT the coolant channels in the block.

With the sight of that rust I'm doubly suspicious of the pump.

[jonesg]

Today, I found that the radiator started leaking on my 2001 V70 T5. It's wet at the junction where the right endtank meets the central core.

Oddly enough, it only seems to drip when it's cooling down after a drive? When the engine is running or when the car sits overnight, everything stays dry and the level in the reservoir stays the same.
Anyone seen this behavior before?

This is the second coolant leak in the last 500 miles, since I flushed all of the gunk out of the system from a failed oil cooler. Last month I replaced the inlet heater core hose, which burst catastrophically.

Could it be an clog in the system? I noticed the bottom radiator hose is very hard when the engine is on, even if the thermostat is still closed.
Isn't the expansion tank cap supposed to vent excess pressure?

Did a couple of test drives while monitoring the actual coolant temperatures and everything behaves as it should with no signs of overheating. Thermostat seems to open when it should, cooling fan cycles at exactly 106 degrees Celsius, heater blows warm air, no temperature gradient across the radiator.
Should also mention I flushed the system with a cleaner product and ran a garden hose through it for almost an hour through the heater hoses, the thermostat housing, the expansion tank, and the top radiator hose until the water came out the bottom so clean you could drink it. No sign of any oil or dirt in the coolant in the expansion tank, it looks very clean.

I have commissioned a CO2 test of the cooling system and a compression test, but I don't think I'll find anything there. Looking for advice if there's anything else I can do other than replacing the radiator and doing another flush, just to have another new leak within a week.

Thanks.

if the top hose is hot the stat has opened, if it blows heat the pump is working.
your radiator has plain worn out along with hoses.

2 yrs ago i had a frozen hose, temp gauge did not move, nothing was circulating, no heat after 1/2 mile, then the top hose blew off and the temp gauge started to work.

[scot850]

Check the engine mount under the crankshaft pulley on the RHS of the car. If this has separated it will allow the engine to move and split the RHS of the radiator. Jack the car up and remove the RHF wheel and support the car. Place a floor jack under the oil pan with a piece of 2" x 4" between the jack and the oil pan. Carefully raise the engine on the RHS and then check from the RHF fender side if the mount separates the rubber from the metal mount on the sub-frame.

Neil.