Coolant Temperature

[nevets]

Soon after setting out for a drive (engine cold and warmed up a bit), I saw the water temp gauge go all the way up to 212, then settle down to about 180 after a few minutes, which is where it stayed, until I stopped for a few minutes. When I started back up, the temp went up again, beyond 212, nearly 230, before quickly settling down to around 180. My thoughts are that the thermostat may be malfunctioning (it's never been changed)? Or possibly the coolant expansion tank I installed recently may be a factor? From experience, I am aware that the temp reading goes way up after a warm engine is turned off, then goes back down once the coolant starts circulating, but this seems out of the ordinary. Any thoughts will be appreciated.

 

[nevets]

More about the issue...I just checked the coolant level and it was down nearly about quarts, which probably explains the temp gauge fluctuations. So, the mystery is...where did the coolant go? I figured the recovery tank would eliminate losing coolant from thermal expansion. Any thoughts appreciated.

 

[gonzo]

Perhaps out the exhaust pipe via blown head gasket or small crack in head near water jacket and cylinder bore? With the expansion tank a seal system condition was created and perhaps more than 7PSI pressures are now experienced.

 

[gonzo]

But definitely check the gage for accuracy and smooth operation.

 

[nevets]

Gonzo, thanks for the response. I’m not seeing signs of a blown head gasket. Running ok, the exhaust is clear, no white smoke. My understanding was that since the expansion tank is vented it should not add additional pressure to the system? I will continue to monitor the situation and post any new findings.

 

[Michael Oritt]

I installed a coolant recovery system which does not create a path for coolant to escape in case of overheating. Depending upon the tank used it is sometimes possible to modify an expansion system and provide for coolant recovery by adding a fitting or two.

 

[Keoke]

I installed a coolant recovery system which does not create a path for coolant to escape in case of overheating. Depending upon the tank used it is sometimes possible to modify an expansion system and provide for coolant recovery by adding a fitting or two.

Any Volvo P1800 overflow tank will meet these requirements and they are small and can be installed on the side of the radiator frame.

 

[Michael Oritt]

An expansion system is not the same thing as a recovery system and will permit the loss of coolant, whereas a recovery system will not.

Most expansion tanks have a nipple on the tank's top face--or high upon a side--to allow for connection of a hose from the radiator neck which permits overflow coolant into the tank. In order to convert such an expansion tank into a recovery tank it is necessary to attach a pipe or hose from the inside of the nipple down to the very bottom of the tank so that as the car's coolant cools off and creates a vacuum the water in the tank will be drawn back through the radiator cap and back into the cooling system.

If the nipple cannot be removed for attachment of such an internal hose one can simply run the overflow hose to a fitting in the bottom of the expansion tank with no internal standpipe, so that the fitting is covered by expansion water which will be drawn back into the cooling system as the car cools off,

In either case there must be a simple vent to atmosphere in the top of the tank to relieve any pressure building up inside the tank from overflow fluid.

 

[nevets]

Thanks for the detailed reply, Michael.

I attached photos of my tank setup. Since the container which is vented at the top, was pre-filled with enough coolant to keep the inlet tube fully submerged, I would think it should allow coolant to return to the radiator as the engine cools?

 

[steveg]

Nevets,
Since your tank input is on the bottom, it'll work fine for recovery. You need an additional thin gasket inside the cap in order for the recovery to work.

From the symptoms, it sounds like your thermostat is acting up. If you don't have a spare, try removing it and comparing the behavior.

 

[Bob_Spidell]

Soon after setting out for a drive (engine cold and warmed up a bit), I saw the water temp gauge go all the way up to 212, then settle down to about 180 after a few minutes, which is where it stayed, until I stopped for a few minutes. When I started back up, the temp went up again, beyond 212, nearly 230, before quickly settling down to around 180. My thoughts are that the thermostat may be malfunctioning (it's never been changed)? Or possibly the coolant expansion tank I installed recently may be a factor? From experience, I am aware that the temp reading goes way up after a warm engine is turned off, then goes back down once the coolant starts circulating, but this seems out of the ordinary. Any thoughts will be appreciated.

Actually, this sounds pretty close to 'normal' behavior, for my two Healeys anyway (a BN2 and BJ8). Obviously, if this behavior started after you installed the expansion tank then that's likely part of the problem--I don't think it is, since you're not losing fluid (are you?)--but since you're holding 180deg while moving I don't think the thermostat is the issue. At any rate, it's an easy test to change it out (230 does sound a little high). But, I have seen bizarre behavior from thermostats before; my '96 Ranger would never get warm/hot, until I found out the thermos have a known sticking (open) issue--some of that German 'quality;' it has a V6 'Cologne' engine--and I installed a new one, but the new one bounces around very similar to what you describe (though it fluctuates at steady driving speeds as well).

 

[nevets]

I will add a thin rubber gasket under the radiator cap...a piece cut from a fat bike inner tube should work. This probably accounts for the fact that I never see any fluid being drawn back into the radiator. Actually I was low on fluid, and yes this behavior is coincidental with installation of the expansion tank. I’ll report back after the gasket is installed. Thanks all for your responses.

 

[Randy_Gay]

There is a particular Stant cap that has the seal in it. Key is to seal at the tank and the cap.

 

[John Turney]

BTW, 212F is the boiling point of water at zero (gauge) pressure at sea level. 230F is the boiling point of water at 7 psig, which corresponds to the relief pressure of the stock radiator cap.