My 1998 V90 has been leaking coolant from the back of the engine block area, the leak has been getting progressively worse, and it leaks worse when the engine is warmed up. I checked the heater hoses (they've been replaced a couple of years ago, and seem in good condition) -- wrapped some paper towels about them and drove around -- the connections seem to be tight, with no leaks. I've come to suspect the metal pipe that connects the inlet (lower) hose to the engine block -- I can get to it by touch and there does seem to be some blackish-greenish stuff under it (a little hard to tell what it is since there's also oil from an oil leak above it --I'm working on fixing that one). It seems like I have excluded pretty much everything else that could leak in that area, but who knows, maybe I've missed something. The location of the thing seems to be the most inconvenient one... wonder if these things are known to leak... should I try to to get the metal pipe or its connector replaced? Not even sure how to get to it -- needs some oxygen sensor type socket probably... For the record, part numbers are 6842264 (coolant pipe nipple) and 3507438 (coolant pipe) (luckily, both still available). Here's a link to a page with parts diagram.
Thanks,
Vlad
--
'98 965

Our 1997 V90 had several coolant leaks in this area. First, I replaced every hose on the car but the leak did not resolve. Closer inspection found that the water pipe which runs from the front if the head under the exhaust manifold had rusted and become porous. It would weep coolant. I wanted to replace the pipe, but it is NLA from Volvo and no aftermarket option. I removed the heat shield, vacuum pump, and preheat assembly. Not wanting to pull the manifold for fear of breaking studs, I had just enough access to wire brush the water pipe and paint with three coats of POR 15. It appears to have worked.

Our car had a second small leak at the back exhaust side corner where the head mates to the block which would drip onto the transmission bell housing and exhaust header. I assumed an external head gasket leak. I added a product called K seal to the coolant and the leak stopped after about 50 miles. I'm not normally a fan of such products, but replacement of the head gasket wasn't really an option.

Update - - To resolve this leak, I ended up replacing the head gasket. It was my first time ever doing one, and it took me a long time but everything went smoothly. The exterior of the engine is bone dry now.

Two thoughts:

1. Try checking for the leak as soon as the engine is warmed up. Then it won't be too hot down there at the inlet. If it gets too hot the coolant will evaporate. Had a somewhat similar problem with my 240 years ago. It would leak through the waterpump seal. Could only see it when the engine first warmed up. After that the cylinder head's heat would evaporate the coolant. Took me a long time to find that one!

2. Have you checked for leaks in other locations? One location for other Volvo engines to leak coolant is the small hose going into the coolant reservoir bottle. Also check for micro-cracks on the bottom of the bottle itself. Finally, thoroughly check the large coolant hose to the block. That one gets a lot of heat!

I used the UV dye. Worked better on the motorcycle than the s 90 since the Fan stirred things up. Since coolant ended up in the tail pipe I ran a bottle of head gasket stop leal (so far) successful.