940 What's leaking?

Might be a noob-ish question but here goes.

It seems I have a small coolant leak somewhere. It's not coming from the thermostat (installed a new one and put a fresh gasket in couple months ago).
There's also a small moist spot on the timing cover.

Is there some spot on the back of the timing cover where there could be a leak or do I need to prepare myself for a new headgasket?
I do not have any obvious issues with the engine that could point to a headgasket issue other than this.

Have you checked that the radiator hose is properly secured to the thermostat housing? A slow/minor leak there looks about like that.

my guess is upper radiator hose drips a little at certain points when the engine is running

Could very well be given it's directly above this spot. Why I did not think of this is beyond me.

Anyway, will recheck the clamp and hose (both new when I installed a new radiator in September last year).

Thanks guys.

I tried to track down this type of leak for a few years before finding a slow intermittent leak at the hose. It can happen on any of the radiator hose ends. If yours is similar, you won't see anything happening when the engine is running, and nothing when the engine is cold. I finally discovered a slow drip that started 10 minutes after the engine was shut off, then stopped as the engine continued to cool.

Check the thermo housing, as electrolysis often eats away at the aluminum housing-to-hose area. IPD has replacement thermo housings.

Amazingly, using 2 clamps on each end did not stop the leaking. I finally stopped it completely by using Permatex high temp silicone sealer on the inside of the connections.
Lazarus

Some hose clamp designs allow them to be tightened tighter than others: might be worth it to upgrade to one of the good ones.

Another thing to keep in mind is how corroded those thermostat housings get. I remove them and wire wheel the mating surface so the hose has a good chance at sealing. That, paired with a new hose (not ?RO preferably), should have you leak free.

There is a freeze plug in the bottom of the head in that general area as well. This leak caused me no end of frustration in tracking it down. It was just a pinhole, but big enough to have a decent leak. You can't get to it unless you remove the head. I would exhaust all other possibilities before checking this

Thanks guys, good tips.

As I recently changed the thermostat I had a good look at the housing and the mating surface and they are in very good shape. I also used a OEM Volvo upper rad hose back in September, so it's pretty much still new.

VB242 said:

There is a freeze plug in the bottom of the head in that general area as well. This leak caused me no end of frustration in tracking it down. It was just a pinhole, but big enough to have a decent leak. You can't get to it unless you remove the head. I would exhaust all other possibilities before checking this

Click to expand...

I'll definitely go that route

Do a pressure test.

I certainly would if I had a pressure tester.

I retightened the hose clamp today, it definitely had some room for a bit of rotation left in it. Let's see what happens.

Fingers crossed for inspection tomorrow. I hope everything's fine (besides the usual bla bla about why the lowering springs, IPD sway bars and the shiny KL intercooler are not registered in the car papers )

Well, doing a pressure test might be interesting, but the symptoms do not point to over-pressure. Over-pressure is usually caused by having the incorrect expansion tank cap. Over-pressure manifests itself in different ways than a slow leak at only one point. In my case, the leak was at the water pump connection, so all the corrosion showed up on top of the power steering pump. It only takes a few drops of antifreeze to start corroding the metal surfaces. The leak always happens when the engine is cooling down. I still maintain that this intermittent leaking started when I replaced the water pump (aftermarket) and the radiator hoses (aftermarket). No amount of tightening will stop it. It is quick and easy to apply some sealant at the hose ends (apply inside the hoses). Let's hope the water is not coming from the cylinder head plug.

Lazarus

You pressurize the cooling system to approx 15 psi and see what leaks.