TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. > The Motobrick Workshop
Symptoms of air trapped in cooling system?
ATXBill:
Hey, this is an old thread but I was wondering if you had any reoccurrence of the light coming on or overheating? I have a very low mileage (1,000m) '90 K75s and am experiencing overheating. I've replaced the thermostat, radiator and reservoir caps, o-ring and of course, fluid. Fan kicks on as it should and blows strongly...sounds fine. But after about 3-4 minutes of the fan being on, the temp light comes on.
Laitch:
--- Quote from: ATXBill on June 09, 2018, 09:22:34 PM ---Hey, this is an old thread but I was wondering if you had any reoccurrence of the light coming on or overheating? I have a very low mileage (1,000m) '90 K75s and am experiencing overheating. I've replaced the thermostat, radiator and reservoir caps, o-ring and of course, fluid. Fan kicks on as it should and blows strongly...sounds fine. But after about 3-4 minutes of the fan being on, the temp light comes on.
--- End quote ---
This is probably being caused by lack of sufficient coolant in the system. Coolant must be added to the radiator slowly, the engine allowed to warm up and then more coolant slowly added. This method allows air to migrate out of the system. The cap is closed when the level is at maximum with time allowed for air to exit, then the reservoir is filled to reach a level between Max and Min. What type of coolant did you use, what type of water was mixed with it, and at what ratio?
Start with this simple method. You can deal with the oil/coolant pump later, if this doesn't work.
ATXBill:
--- Quote from: Laitch on June 09, 2018, 09:53:04 PM ---This is probably being caused by lack of sufficient coolant in the system. Coolant must be added to the radiator slowly, the engine allowed to warm up and then more coolant slowly added. This method allows air to migrate out of the system. The cap is closed when the level is at maximum with time allowed for air to exit, then the reservoir is filled to reach a level between Max and Min. What type of coolant did you use, what type of water was mixed with it, and at what ratio?
Start with this simple method. You can deal with the oil/coolant pump later, if this doesn't work.
--- End quote ---
Brand new Motul Motocool Expert Coolant, installed by a BMW certified mechanic. Reservoir level was right in-between MIN & MAX. Rode it 150 miles today. First 125 miles were no problem, though a lot of higher speed highway miles. When I went into some twisties at slower speeds (35-40mph), that's when the problems began. I pulled over 4x and let it cool down before riding again. Problem repeated within 10 minutes each time. Got home, let it cool off for an hour. Started it and idled for about 8 minutes before the fan kicked on. After about 3 minutes of fan, the temp light came on again. Fluid level in reservoir hasn't deviated.
alexg:
Search on this forum for “strange overheating conditions “. Your symptoms are very similar to the one problem I had. Filler cap check valve stuck.
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ATXBill:
--- Quote from: alexg on June 09, 2018, 10:26:34 PM ---Search on this forum for “strange overheating conditions “. Your symptoms are very similar to the one problem I had. Filler cap check valve stuck.
--- End quote ---
Thanks Alexg. I had the filler cap replaced. Is the check valve a separate part or embedded in the cap? I'll do the search you mentioned...thanks again for the quick reply!
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