SwedeSpeed - Volvo Performance Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
73 Posts
Discussion Starter · #1 ·
I have a 1968 P1800s, B18 engine, and the coolant comes out of the expansion bottle holes once it gets to temperature. The holes had been taped up to plug them by the previous owner. I pulled the tape off when changing the coolant. My guess is I need a new expansion bottle cap, but would like input before just buying parts. Thanks.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
2,569 Posts
I have a 1971 142E. The pressure cap is on the expansion bottle and the cap on the radiator is just a seal cap. Is the '68 P1800 the same way? If so, my first reaction is perhaps the system is over filled if its venting significant fluid. On my 142 E, the fill process is remove the expansion bottle pressure cap' but, fill coolant from the radiator cap until it comes to the bottom of the rad neck. Start the engine and let it warm up and top up with coolant to maintain liquid level at the bottom of the neck. Once the coolant starts to rise in the neck, put the cap on the rad and watch coolant level in the expansion bottle. With the engine close to operating temperature the coolant level in the bottle should be about mid point in the bottle - add coolant if required to meet that level and cap the expansion tank. Allow the engine to cool then start up and check level in bottle once up to operating temperature. Add coolant if necessary to reach mid point.

If your engine is not overheating, you should not be venting coolant from the bottle. If the bottle design is similar to the 140, fluid has to reach the top of the bottle to vent. That is a sign of running too hot or overfilling the cooling system.

If the system has been filled correctly, the engine is not overheating and you are just venting tiny amounts of fluid, then the pressure cap on the bottle may be weak. The definitive test would be a cooling system pressure test by pressurizing the system from the rad cap. If the expansion bottle pressure cap vents below the spec in the Volvo service manual then you need a new pressure cap. Or you can buy a new one on spec. Be careful where you buy the cap. I seem to recall that some of the 'generic' pressure caps cross listed to fit the Volvo bottle do not seal correctly.

As an observation, if the previous owner blocked off the expansion tank vents and the cooling system incurred sustained over pressurization as a result, the cooling system hoses may have incurred stretch damage and worse the heater core may have been damaged. Perhaps give all the connections an eyeball check and check for coolant weeping from the heater - just to err on the side of caution.

If your system is different than the 140 system - then just ignore all of the above!
 

·
Registered
Joined
·
556 Posts
SSchultze;

142g's explanation of sealed Cooling Sys for 140s also applies to your 1800 with sealed CS. In normal operation, level in Exp Bottle would go from about low 1/4 level to about 3/4level [Edit: This would obviously be a function of level of fill and sys temp, see link!]...unless Pressure Cap is somehow not sealing, not allowing pressure to build which might lead to a lower boiling point, bubbles in the Cyl Head, and Coolant level in Exp Bottle rising even more, then getting lost...[Edit: Condition 4 at Link] So the first thing I'd do is pressure check the CS...if possible with a tester which replaces Rad Cap with a cap with a fitting which allows you to pump up pressure...that will enable you to check if pressure can build to setpoint before Pressure cap releases it.

See also: https://www.sw-em.com/Cooling_System.htm#early_open_cooling_systems_vs_later_sealed_cs
and: https://www.sw-em.com/Cooling_System.htm#closed_cooling_system

Good Hunting!
 

·
Registered
Joined
·
2,569 Posts
SSchultze;

142g's explanation of sealed Cooling Sys for 140s also applies to your 1800 with sealed CS. In normal operation, level in Exp Bottle would go from about low 1/4 level to about 3/4level...unless Pressure Cap is somehow not sealing, not allowing pressure to build which might lead to a lower boiling point, bubbles in the Cyl Head, and Coolant level in Exp Bottle rising even more, then getting lost... So the first thing I'd do is pressure check the CS...if possible with a tester which replaces Rad Cap with a cap with a fitting which allows you to pump up pressure...that will enable you to check if pressure can build to setpoint before Pressure cap releases it.

See also: https://www.sw-em.com/Cooling_System.htm#early_open_cooling_systems_vs_later_sealed_cs
and: https://www.sw-em.com/Cooling_System.htm#closed_cooling_system

Good Hunting!
Good point about expansion and overflow due to boiling in the cooling system because of low system pressure. I lost sight of the fact that the OP is from TX so the cooling system is slightly more heat challenged than what I experience north of the 49th parallel. The only time I get my coolant temp to nudge past 100 C is coming off the highway on a hot day and coming to a quick stop. Most of the time, if it were not for the fact that the coolant would splash about in the engine compartment I could probably drive with no cap on the expansion bottle; but, I am not going to try that :).
 

·
Registered
Joined
·
73 Posts
Discussion Starter · #6 ·
Thanks for everyone’s insight. I’ll get a coolant system pressure tester next week and see what happens from there.
 

·
Registered
Joined
·
73 Posts
Discussion Starter · #7 ·
Thanks for all the assistance on this. I pressure tested first and the overflow bottle cap was passing by immediately. A new cap bought and installed and everything is working great now.
 

·
Registered
Joined
·
2,569 Posts
Excellent - that is a cheap and easy fix.
 
1 - 8 of 8 Posts
Top