[MR2] MK1 Coolant Problem

[Dennis McFayden]

Donald,
 
Yes to both questions. I also replaced the radiator cap with a couple of different new OEM caps but no improvement. I also pressurized the recovery hose at the same time that I pressurized the complete system. I plugged the bottom of the tube that normally goes into the recovery tank with my pressure gauge. The pressure held at 16 PSI for more than one hour with no change. 
 
During the pressurization I did see a clue to the problem. The tube that goes into the recovery tank did not hold the pressure. It blew off. I know that the normal pressure at this point is less than two atmospheres but it was still a possibility. I added a spring clip to the hose where it attaches to the cap for the pressure test. I also kept the clip in place to see if it changes the results. 
 
I did take the car for a short 8 mile drive tonight and it does seem to have made a difference. The temperature hasn't dropped low enough to see if it has recovered all of the coolant but it has improved. 
 
A vacuum leak at this hose junction would be the answer to the problem. Hard to believe it could change that much with temperature. The hose seems to be a pretty good fit when cold but that obviously changes with temperature. 
 
Dennis

--- On Sun, 9/20/09, Donald Chalfant <dkchal at datasync.com> wrote:


From: Donald Chalfant <dkchal at datasync.com>
Subject: Re: [MR2] MK1 Coolant Problem
To: "Dennis McFayden" <mr2garage at yahoo.com>, "MR2 Email" <mr2 at mr2.com>
Date: Sunday, September 20, 2009, 8:44 PM


The physics of the occurrence are fairly straight forward.  The coolant in
the system heats up, expands, and an amount (usually equal or a little less
of the volume in the expansion tank between cool and hot)  is forced past
the coolant fill (radiator) cap.  When the engine is shut off, the coolant
in the inside undergoes a lessening of volume with the decrease in
temperature and a void in the coolant system is filled by the atmosphere
pushing the liquid in the expansion (overflow) tank back under the radiator
cap.  If the cap is seated too tightly, the fluid will not go back. If the
hose and or lid to the expansion tank will allow air to leak out, then the
fluid will remain in the expansion tank, and the cooling system will have a
void which will have room for the expanding coolant the next time the engine
is heated.     Was the replacement system working on the other vehicle?  If
yes, did you use the radiator cap from that vehicle?


 
 
Donald,
 
Yes to both questions. I also replaced the radiator cap with a couple of different new OEM caps but no improvement. I also pressurized the recovery hose at the same time that I pressurized the complete system. I plugged the bottom of the tube that normally goes into the recovery tank with my pressure guage. The pressure held at 16 PSI for more than one hour with no change. 
 
During the pressurization I did see a clue to the problem. The tube that goes into the recovery tank did not hold the pressure. It blew off. I know that the normal pressure at this point is less than two atmospheres but it was still a possiblity. I added a spring clip to the hose where it attaches to the cap for the pressure test. I also kept the clip in place to see if it changes the results. 
 
I did take the car for a short 8 mile drive tonight and it does seem to have made a difference. The temperature hasn't dropped low enough to see if it has recovered all of the coolant but it has improved. 
 
A vacuum leak at this hose junction would be the answer to the problem. Hard to believe it could change that much with temperature. The hose seems to be a pretty good fit when cold but that obviously changes with temperature. 
 
Dennis

--- On Sun, 9/20/09, Donald Chalfant <dkchal at datasync.com> wrote:


From: Donald Chalfant <dkchal at datasync.com>
Subject: Re: [MR2] MK1 Coolant Problem
To: "Dennis McFayden" <mr2garage at yahoo.com>, "MR2 Email" <mr2 at mr2.com>
Date: Sunday, September 20, 2009, 8:44 PM


The physics of the occurrence are fairly straight forward.  The coolant in
the system heats up, expands, and an amount (usually equal or a little less
of the volume in the expansion tank between cool and hot)  is forced past
the coolant fill (radiator) cap.  When the engine is shut off, the coolant
in the inside undergoes a lessening of volume with the decrease in
temperature and a void in the coolant system is filled by the atmosphere
pushing the liquid in the expansion (overflow) tank back under the radiator
cap.  If the cap is seated too tightly, the fluid will not go back. If the
hose and or lid to the expansion tank will allow air to leak out, then the
fluid will remain in the expansion tank, and the cooling system will have a
void which will have room for the expanding coolant the next time the engine
is heated.     Was the replacement system working on the other vehicle?  If
yes, did you use the radiator cap from that vehicle?



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