[DMCForum] Continuing misadventures of a Volvo/B280F PRV

["cartermartin" <cartermartin@xxxxxxxxx>]

Sorry in advance for the long post.

Ok so I think I have gotten to the bottom of my Volvo 760GLE/B280F-
PRV problems or at least nearly to the bottom of it. 

I have essentially rebuilt my  cooling system. Along the way I did 
every possible test I could think of for a blown head gasket or 
cracked head. These include:

- Compression test. I got 180-185# on all 6 cyl. The numbers might be 
suspect but felt the fact they are so close together was more 
important.
- Cooling system pressure test. After all the cooling system work was 
done. I pressure tested it at 22# (factory spec for this model) for 
15-20 minutes. I had very little, if any, leakage.
- Tested the cooling system pressure under normal running conditions. 
Pressure was built gradually up to 15-20# or so.
- A block leak test. The gizmo that detects exhaust gasses in the 
coolant by drawing air thru the coolant.

Anyway after all of this I still have coolant loss and evidence of 
high pressure in the system. In this case coolant blown out of the 
expansion bottle.

The only other clue was the chocolate milkshake on the filler cap. 
When I changed the oil I found no evidence of coolant.  And after 2 
negative 'block leak' tests (i.e. no combustion gasses) I finally got 
a positive after a highway run (where btw it urped out a pint or so 
of antifreeze).

It appears that under light load, idling or driving around the 
neighborhood, there is not a problem. This manifests itself at 
freeway speed when I hear a buzzing sound from time to time that I 
believe is either the pressure being vented past the radiator cap or 
perhaps even gasses blowing past the head gasket. The latter may be a 
long shot but the sound is coming from the opposite side of the 
engine from the coolant bottle.

At this point my suspicion is either:

- small head gasket leak
- Cracked head
- or maybe a seal for the cylinder liner?

I'm still a neophyte on these engines and since it's an old Volvo 
sedan (as opposed to something more exotic) I should probably walk 
away. But I feel I want to get to the bottom of all of this. It is 
also difficult because it's running SOOOOO good.

Any thoughts, ideas, or suggestions would be appreciated? Any PRV 
mechanics in the Atlanta area who can do a head/head gasket, please 
step forward.

Oh and for what it's worth I did get the Y-Pipe o-rings sealed up. 

Carter

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