I finished restoring my 1962 PV544 and added an auxilary coolant recovery bottle to the new radiator, which wasn't part of the stock system. What type & pressure caps should I use on: (1) the radiator and (2) the recovery container?

Also, I seem to have very high temperatures in the heater hoses, even though the dashboard temp guage shows everything in the middle of the range. Would this be a problem with air in the system and, if so, how should I "burp" the system to get it out? The radiator is brand new.

We have several upgrades to the cooling system we suggest doing and adding an expansion tank is 1 of them.

Before we begin, it should be clear that there are 2 basic types of radiator caps used on the old Volvos and although they look identical, there is 1 big difference and that is the length of the plunger. There's a 1" deep radiator filler neck and a 3/4" deep neck. BTW this also applies to the Volvo expansion tanks as those were made in both styles.

To add an expansion tank to any Volvo cooling system with a pressure cap on the radiator, we use a blanking cap to seal the radiator fill neck and connect the expansion tank to the stock radiator dump tube using the correct style of coolant recovery hose and it's not fuel hose.

If you have the early expansion tank that has a 1" deep neck, we use a 7 lb pressure cap. If it's the later tank with a 3/4" deep neck, then we use a 13 lb cap.

If we're doing a radiator service at the same time, we recommend replacing the 1" upper and lower radiator hose barbs with 1 1/4" barbs on the radiator for better flow. Larger hoses and the 1 1/4" thermostat neck also need to be installed at the same time.




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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

I used a radiator from a civic and its cap is at 1.3 atm. the aftermarket exp tank has a 1.1 atm cap. i didnt choose these pressures....they are just what they came with. The system works fine. It runs flooded and then pressures into the tank when very hot. The vac breaker in the radiator cap then pulls that liq back in when cold.
dean

I got my cap at a regular auto parts store - from what I can see, the cap will release coolant to the bottle when the pressure in the system reaches the value printed on the cap, and has a check valve that allows coolant back into the system as the engine cools.

The bottle should have an overflow and a regular cap.

When I started to use the system I filled the radiator to the top and filled the bottle a little less than half full.

Then I observed what happened when the engine was warmed up and fully cooled.

Adjust to suit.