Reviving a barn find P1800ES

[142 Guy]

Progressing nicely.

I suggest that you do not bother with back flushing the radiator. Take it directly to a radiator shop and have them clean it in a caustic bath and then flush and pressure test it. My 1971 142 has a cross flow radiator which is different that the 1800. The lower 1/3 of the radiator tubes were blocked about mid way across the radiator. No amount of back flushing would dislodge the blockage and the caustic clean was the only way to restore the radiator..

On my 140 E, when the ambient temperatures are border line freezing the interior heater can reject enough engine heat into the interior to mask problems with the radiator. Be cautious about assessing the degree of impairment of the radiator when testing in cold weather with the heater valve open.

When it comes to bleed the brakes, be sure to follow the bleeding sequence in the service manual. This will reduce the amount of fluid (and frustration) you have to run through the system to get a good bleed. A pressure bleeder makes bleeding the Volvo dual diagonal brake system much easier and if your master cylinder is original avoids the risk of damage to the piston seals in the MC from running the piston past the wear ridge in the bore.

My 142 E is a low use car. As a result, I use DOT 5 silicon brake fluid in the hydraulic system. DOT 5 has the advantage that it is hydrophobic so does not absorb moisture from the air like non silicon fluids. This allows you to safely extend the flush intervals to at least 5 years. DOT 5 will not damage paint if you have a spill which may be a consideration if you anticipate some weeping at the connections after you do the repair work. DOT 5 is more expensive and must not be intermixed with non DOT 5. It is also not acceptable if you intend to go racing.

The problem you described with the brakes failing to release could have been due to sticky calipers. However, old flex lines are also noted for swelling with with age which slows release of pressure in the caliper and retraction of the pistons. New calipers and flex lines should eliminate those possibilities.