cpjlawyer Posted July 17, 2010 Report Share Posted July 17, 2010 (edited) I recently had my engine completely rebuilt. Driving in town, I don't have any problems, driving on the road however, the car overheats. The guage goes to the red, but with no boil over. I checked the thermostat (good), coolant level (full), and the radiator looks to have good water movement at idle. I have a mechanical fan (red 13 blade instead of yellow 9 blade). I also replaced the radiator cap and went to a 13psi cap. I recently took the car out for a spin and got a whopping 9 miles before the temp. gauge went to the red line. I'm suspecting an air lock in the block. Is there such a thing as a bleeder valve for the cooling system? My mechanic is suggesting (without seeing) that I replace the radiator, but I'm not convinced that is needed because of the visible rapid coolant movement at idle with the radiator cap off. Suggestions? Chris J. Edited July 17, 2010 by cpjlawyer Quote Link to post Share on other sites
jmo Posted July 17, 2010 Report Share Posted July 17, 2010 hi had this problem last week when i changed the coolant on my 72 pi , turned out to be an airlock . System had to be full topped right up with expansion bottle held above the level of the cap with the engine running to clear the airlock . even then it pulled another pint or so out of the bottle when i put it away after a run . Quote Link to post Share on other sites
Jersey Royal Posted July 17, 2010 Report Share Posted July 17, 2010 Have a look on the block above the starter motor, you will find the block bleed tap. Most likely full of crud so poke some wire in it to release. Cheers Guy Quote Link to post Share on other sites
foster461 Posted July 17, 2010 Report Share Posted July 17, 2010 Have a look on the block above the starter motor, you will find the block bleed tap. Most likely full of crud so poke some wire in it to release. Cheers Guy Guy, I dont think the engine drain plug is a good air bleed point as it is too low in the system. I have seen some people drill and tap a hole in the thermostat cover to release air and then seal the hole with a bolt and fiber washer or play tricks with raising the front of the car etc. The air wants to go to the highest point in the system. Stan Quote Link to post Share on other sites
88V8 Posted July 17, 2010 Report Share Posted July 17, 2010 When the engine was rebuilt, this should have included clearing out the waterways in the block, especially at the back, and replacing the drain tap or at least checking it works. The normal method of bleeding the system is to pull the top hose off the heater valve (valve open) and idle the engine until water comes out. If the rad is old and partially blocked then the temp will tend to increase when running as opposed to idling, hence your mechanic's recommendation I suspect. To check the rad, get it hot, then spray it with water from a plant mister and idle the engine. The areas that don't dry rapidly are blocked. Backflushing may improve things, otherwise a new rad or a recore would be the solution. Wrong ignition timing can also cause overheating, as can weak mixture. And a faulty thermostat. And a duff temp sender can start a wild goose chase of course. Ivor Quote Link to post Share on other sites
Jersey Royal Posted July 17, 2010 Report Share Posted July 17, 2010 (edited) Guy, I dont think the engine drain plug is a good air bleed point as it is too low in the system. I have seen some people drill and tap a hole in the thermostat cover to release air and then seal the hole with a bolt and fiber washer or play tricks with raising the front of the car etc. The air wants to go to the highest point in the system. Stan Stan, You are right, i am still on French time and recovering from Le Mans and my extended trip. Another way would be to fit a blanking cap to rad, then take the overflow pipe and put it into a metal type expansion tank ( similar to mg), fit original cap from rad to expansion tank. Expansion tank is fitted high up on wing, and the overflow from that can go into bottle. I have done this on mine and it works well. Picture shows tank, but i have changed the routing of the pipework since this photo was taken. Cheers Guy Edited July 17, 2010 by Jersey Royal Quote Link to post Share on other sites
cpjlawyer Posted July 17, 2010 Author Report Share Posted July 17, 2010 Thanks everyone. I now have some things to try. CpjLawyer. Quote Link to post Share on other sites
stuart Posted July 17, 2010 Report Share Posted July 17, 2010 Stan, You are right, i am still on French time and recovering from Le Mans and my extended trip. Another way would be to fit a blanking cap to rad, then take the overflow pipe and put it into a metal type expansion tank ( similar to mg), fit original cap from rad to expansion tank. Expansion tank is fitted high up on wing, and the overflow from that can go into bottle. I have done this on mine and it works well. Picture shows tank, but i have changed the routing of the pipework since this photo was taken. Cheers Guy Hmm I think its time I patented my idea Stuart Quote Link to post Share on other sites
Jersey Royal Posted July 17, 2010 Report Share Posted July 17, 2010 Hmm I think its time I patented my idea Stuart Yup, It was all Stuarts idea Simple and effective Thanks Again See ye and Albert Thursday Cheers Guy Quote Link to post Share on other sites
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