1. Not clear what you mean re the thermostat housing part... That only has one large hose going to the top of the radiator and seals to the block, carries coolant.

2. No, no way you can oil from there (the mount to the block)... It's travelling from somewhere else... most likely above, could be a head gasket leak--they tend to leak from around there.

 

1. It's Part #7 in the picture above (looks the same for the 1993 set up linked above). It's called the "thermostat housing" in the figure above. Oil appears on the bottom of the curvy hose ready to drop. Or maybe it's coolant? It seemed like oil (slippery between the fingers in the darkness of under the car) but I'll double check next time. It is the most consistent clue I have - *always* liquid on the bottom of that curly tube upon every inspection. I suppose it could be oil blowing back from leak #2 during driving or it must be coming from that o-ring just above (and "behind" the filter). Or it's just coolant and the new hose should fix that.

2. Thanks for that. I'll focus attention again on that o-ring and the head gasket.

I wish I could trigger the leak under idle in the driveway - but it's such a small (but consistent) leak and only appears after driving.

 

OK, never mind! I wasn't looking at that picture, that thermostat! Never knew that was also called a thermostat... No idea what it does or how...

 

Your 4th picture (shows bell housing vents) also shows the coolant drain at the far right. Loosen that up, put a pan under it and most of the coolant in that part of the system will drain. I replaced those two hoses with silicone ones from ipd because they are much more resistant to oil.

Part #7 is the oil cooler, I don't know why it's labeled thermostat.

The oil seal between the standoff and the block should be replaced, it is almost surely the culprit, since there is almost no other leak point. The standoff and oil cooler (thermostat) have an oil seal there that causes the leak onto the two cooler hoses. An important note, the cooler can be "clocked" when reinstalling it so that the two hoses are easier to install. The nut that holds it to the standoff is not very robust, so don't over tighten it. The standoff banjo bolt can take some good tightening.

The squashed o ring at the top of the waterpump is not the problem there, however if you were to pull off the timing belt and check behind the plastic shield you will probably see an oil leak coming from the cam shaft seal. Mine has always weeped a little.

Finally, I'd go back to the turbo oil line and return. They will leak and it doesn't take much to make a mess.

 

Thanks, admasters, I was certainly heading in that direction and already placed an order for those two o-rings and coolant hoses just the other day. Thanks for the tip on how to drain the fluid in that area and to clock the cooler to get the hoses back on. I've been looking at that banjo fitting. It looks like I can sneak a cheater bar in there from the top-front to loosen it up. Or must I remove the mounting bracket or something else first to get access?

I should have included in my order the seals or o-rings for the two turbo oil line fittings just to have ready in case. But my order has already shipped.

 

The oil seals are available from your Volvo dealer, I am pretty sure they are green, so you will know if you get the right ones.
There is a hang up that might give you some trouble; the standoff is supported by a small bracket that shares a bolt with the engine mount. My picture shows an engine that probably looks like yours, but you can clearly see the bracket piece. Judging by the clean area, it looks like the bracket is on top of the engine mount and the bolt goes through it first and then the mount second.



I removed the assembly in pieces as I worked; coolant return hoses, oil cooler, then standoff. The banjo is the only thing holding the standoff to the block and that shouldn't be too hard to remove.
If you are doing the turbo oil return line, it might be tricky (my engine was out), but I had to loosen and carefully suspend the vacuum wastegate actuator in order to the the oil return line off because I didn't want to mess with any manifold bolts. By doing that I created some swing room so that I could rotate the return line away from the block and turbo (toward the fender) and then pull it upward from the oil ring at the other end (red if I recall). I reinstalled it the same way because there is wiggle room. Put the oil seal on the end of the return line, wiggle it into the block and then rotate it back into place with the new gasket on it. Finally, reattach the vacuum actuator to the turbo.

 

Thanks for that, admasters, all you said is clear and understood. I had no idea about that extra bracket - I'll double check later to see if I have that bracket (car is out on the road with my daughter today). I've been scouring the internet to learn as much as I can on how to remove the oil cooler standoff. I'm reading that removing the power steering (without disconnecting the fluid lines) is helpful to gain access to the banjo bolt. In the end, I plan to document how I do it with photos and post to this thread. I'm reading that these o-rings are a common source for oil leaks but videos or descriptions for how to change them are rather thin,

 

So my oil leaks appear solved! I replaced both o-rings, and things look dry after a few days of driving. For anyone contemplating this job in the future, here are a few notes that might help you along the way. I did the job in my driveway without raising the car - but I'm a skinny guy, haha.

To get purchase on the 32mm banjo nut holding the fuel filter/cooler standoff requires the removal of the power steering unit. Loosen three 12mm bolts and the adjustment nut and the power steering unit will hang down and out of the way without tampering with the fluid hoses.

Then there is the bracket that admasters mentioned in his post above. If you remove the top-left bolt holding the engine mount bracket to the block (identified in his photo above), then the standoff comes free. The standoff bracket goes *over* the engine mount bracket, so no other bolts need to be touched in this area.

Removing the two coolant hoses is straight forward, Both of my hoses were very swollen from age, thus the clamps needed to be opened up very widely to get them off. Then the hoses pull out and the standoff unit will come free from the car. Here it is on the bench. Note the clamp. I guess you could instead remove the torque screw and only loosen the top-left engine mount bolt. But removing the bolt entirely was easier for me - access is ample.



I lost about a gallon or two of engine coolant during the operation. I first opened the bleeder valve to let it pour out. But it just kept coming out little by little for a long time. So have something handy to catch the coolant. I got plenty wet.

Removing the oil cooler from the standoff unit is done on the bench and requires a 27mm socket and a vice to hold the standoff unit. Once the center bolt is removed, then the parts separate and the o-ring comes into view. Mine looked spent - it appears from the crud trail that the leak started from the top.



So that o-ring was replaced after carefully cleaning everything without scoring the surfaces.

The other o-ring, between the standoff and the block, didn't look as bad ...



My guess is that the oil leak here could have been repaired by simply torqueing the banjo bolt (I recall how easy it was to loosen the banjo bolt - I was preparing for a fight when it came loose without hardly any torque). But replacing the o-ring and then torquing the banjo bolt was just as easy.

It took just under 4 hours. Most of the time was spent fiddling with the clamps on the coolant hoses with coolant dripping out on me (fun, haha).

Recall that the drivers side of my engine had a leak too. My oil separator did not have the green o-ring - and I added that. Also, the hose that connects the flame trap housing to the manifold was, well, not attached to the manifold for who know how long (years or decades?). My guess is that trace quantities of oil splattered out of that open hose for years and soiled the drivers side of the block. The hose was fitted and no new oil appears there. But I continue to inspect.

I hope this pointers might prove helpful to someone doing this to their Volvo. Thanks to all that helped me along the way. Next job, a click in my steering. But I will start a new thread for that.