TR3BGeorge Posted July 20, 2009 Report Share Posted July 20, 2009 As I may have told you, I have been haunted by a small coolant leak. The first time was my fault, as I filled up the neck with antifreeze when I first got the car, not realizing that the bottom of the neck is the correct level. Regardless, I have cleaned and recleaned my engine compartment 3 times. Last night I went to a car show and sat with my RRTC fellow members. Stopping by for a visit was Garry Dockree, an ex-patriot Brit from Selsey, a little town between Brighton and Portsmouth, who had his own shop there. He has a body shop here in the Dallas area, also does mechanical work, and does our club's body work. I was bemoaning my dilemma, and he said, "I don't want to belabor the obvious, but have you checked your radiator cap? It could be defective." So, this morning I went to O'Reilly's and bought a 7-lb cap for 5 bucks. I took off the old one and noticed.................[drum roll]....................THAT THERE WAS NO RUBBER WASHER IN IT!! It was making metal-to-metal contact!! So, I am going to clean the engine compartment tomorrow, and take her out for a good drive to see if I still have coolant all over everything. Could it be that simple? Can I solve this problem for 5 dollars?? Quote Link to post Share on other sites
Richardtr3a Posted July 20, 2009 Report Share Posted July 20, 2009 The cap will only need a rubber sealing washer. If you move to a higher pressure than 4 lbs the leaks will appear elsewhere, i.e.thermostat housing and hoses. Have you got a small overflow pipe routing any expansion below the engine? Quote Link to post Share on other sites
angelfj Posted July 20, 2009 Report Share Posted July 20, 2009 (edited) As I may have told you, I have been haunted by a small coolant leak. The first time was my fault, as I filled up the neck with antifreeze when I first got the car, not realizing that the bottom of the neck is the correct level. Regardless, I have cleaned and recleaned my engine compartment 3 times. Last night I went to a car show and sat with my RRTC fellow members. Stopping by for a visit was Garry Dockree, an ex-patriot Brit from Selsey, a little town between Brighton and Portsmouth, who had his own shop there. He has a body shop here in the Dallas area, also does mechanical work, and does our club's body work. I was bemoaning my dilemma, and he said, "I don't want to belabor the obvious, but have you checked your radiator cap? It could be defective." So, this morning I went to O'Reilly's and bought a 7-lb cap for 5 bucks. I took off the old one and noticed.................[drum roll]....................THAT THERE WAS NO RUBBER WASHER IN IT!! It was making metal-to-metal contact!! So, I am going to clean the engine compartment tomorrow, and take her out for a good drive to see if I still have coolant all over everything. Could it be that simple? Can I solve this problem for 5 dollars?? George: Yes, it could be that simple. However, here is something else to consider. From your photos, it appears that your car was restored recently. I will assume that the parts came from one of the three major suppliers here. We discovered while testing my 3A for coolant leaks that both the engine block and radiator drain cocks leaked. The leak was not at the threads where they thread into their bungs. They actually leak right past the seats, enough to make a large puddle overnight. We ordered three new drain cocks, one from each of the major suppliers. They were all identical and they all leak. In order to maintain genuine appearance we soldered a plug in both drain cocks and replaced them. When we need to drain the system we will merely remove the useless drain cocks and empty the system for flushing , etc. Sorry to go on ad nausiam, but perhaps you are losing coolant in this way. Edited July 20, 2009 by angelfj Quote Link to post Share on other sites
stuart Posted July 20, 2009 Report Share Posted July 20, 2009 I would go for a 4lbs cap (Standard original pressure) otherwise as stated you may find lots of leaks elsewhere Stuart Quote Link to post Share on other sites
Kiwifrog Posted July 20, 2009 Report Share Posted July 20, 2009 Check the lenght of the plunger on the cap as well. Some are shorter than others and do not sit correctly on the mating surface, ask me how I know Alan Quote Link to post Share on other sites
vivdownunder Posted July 20, 2009 Report Share Posted July 20, 2009 And TR3BGeorge, better check if your radiator needs an original 1" long throw cap, or if the neck has been replaced to suit a modern .75" throw cap. You can usually get away with a 7lb cap instead of the proper 4lb if the radiator hoses are new-ish, but go over all the hose clamps to ensure they are tight, including the heater hoses, if fitted. Sometimes hoses only leak when under pressure, which can be a bit hard to spot. Regards, Viv. Quote Link to post Share on other sites
RandallD Posted July 20, 2009 Report Share Posted July 20, 2009 Related to this topic, does anyone know the original AC part number for the appropriate TR3 radiator cap (ie. RC-1,2,3?) Regards, Randy Quote Link to post Share on other sites
Don Elliott Posted July 20, 2009 Report Share Posted July 20, 2009 The four psi radiator cap on my 1958 TR3A is stamped with GRC 103 on the ear at one end and the ear at the other end has a numeral 4 stamped there. I can't say if any of this means anything. This cap wa bought from a TR parts supplier, either the one I bough in 1987 from Cox and Buckles of the one I bought from Roadster Factory about 10 years ago. Quote Link to post Share on other sites
RAHTR4 Posted July 20, 2009 Report Share Posted July 20, 2009 Related to this topic, does anyone know the original AC part number for the appropriate TR3 radiator cap (ie. RC-1,2,3?) Regards, Randy Randy, The original AC 4lb radiator cap is referenced RC3, as photo below. The box states that the cap depth should be 1.4" greater than the radiator neck. For some reason when the TR4 came along cap was changed to a 7lb RC4. Regards, Richard Quote Link to post Share on other sites
TR3BGeorge Posted July 21, 2009 Author Report Share Posted July 21, 2009 Hey Guys, thanks for the poop. The cap I took off was a 4 pounder. However, looking at TRF's price list, they list the 4-pounder for the TR2-3, and the 7-pounder for the TR3-4. I have a TR4 engine, so I went with the bigger number. However, I WILL take a long look at my hoses, and the clamps. I suppose that clamps can ALWAYS be tightenend some. Also, I will look at the petcocks, although I suspect that my leak was up high, as everything up high was coated with coolant, while it was cleaner down below. Thanks again. I am doing little "fun stuff" now, while waiting for my door pockets, vacuum pipe, and hood stick cover to get here. Today I installed some jury-rigged brackets to hold my radio in, and painted the handle on the heater valve green. It's a tough life, being retired. I feel guilty. Also, I never even CONSIDERED the length of the radiator cap. I just assumed that they were all the same. All I can do is put the old one beside the new one, and see if they are the same. If not, I guess that I can go back and see if they have a shorter or longer one. Of course, THAT is assuming that the one on there was correct. It was made in England, so I suspect that it was the right size. Thanks again. P.S. The club-members asked me why I didn't drive my TR to the car show the other night. I told them that I didn't have the decals for my air cleaners. P.P.S. I am dreading putting her up on jack stands and cleaning off the oil underneath. Is there an easy way? Prayer, perhaps? Quote Link to post Share on other sites
RandallD Posted July 21, 2009 Report Share Posted July 21, 2009 Randy, The original AC 4lb radiator cap is referenced RC3, as photo below. For some reason when the TR4 came along cap was changed to a 7lb RC4. Regards, Richard Richards, many thanks - it was impossible for me to find that in a websearch (until now that is!) Regards, Randy Quote Link to post Share on other sites
Dave Larnder Posted July 22, 2009 Report Share Posted July 22, 2009 Randy, The original AC 4lb radiator cap is referenced RC3, as photo below. The box states that the cap depth should be 1.4" greater than the radiator neck. For some reason when the TR4 came along cap was changed to a 7lb RC4. Regards, Richard Hi Richard Just checked my cap and it's an RC4 with HO stamped on it opposite the RC4 and 4lb in the red circle. It corresponds exactly with you chart at 1.25" overall length with 1" inside the neck of the rad. Dave Quote Link to post Share on other sites
Kevin in CT Posted July 24, 2009 Report Share Posted July 24, 2009 Hey Guys, thanks for the poop. The cap I took off was a 4 pounder. However, looking at TRF's price list, they list the 4-pounder for the TR2-3, and the 7-pounder for the TR3-4. I have a TR4 engine, so I went with the bigger number. However, I WILL take a long look at my hoses, and the clamps. I suppose that clamps can ALWAYS be tightenend some. Also, I will look at the petcocks, although I suspect that my leak was up high, as everything up high was coated with coolant, while it was cleaner down below. Thanks again. I am doing little "fun stuff" now, while waiting for my door pockets, vacuum pipe, and hood stick cover to get here. Today I installed some jury-rigged brackets to hold my radio in, and painted the handle on the heater valve green. It's a tough life, being retired. I feel guilty. Also, I never even CONSIDERED the length of the radiator cap. I just assumed that they were all the same. All I can do is put the old one beside the new one, and see if they are the same. If not, I guess that I can go back and see if they have a shorter or longer one. Of course, THAT is assuming that the one on there was correct. It was made in England, so I suspect that it was the right size. Thanks again. P.S. The club-members asked me why I didn't drive my TR to the car show the other night. I told them that I didn't have the decals for my air cleaners. P.P.S. I am dreading putting her up on jack stands and cleaning off the oil underneath. Is there an easy way? Prayer, perhaps? Hi 'TR3BGeorge'- RE: Your P.P.S.- Yes there is an "easy way", which I found while prepping my BMW 2800CS for a concourse event years ago. Hire a skillful, patient and meticulous neighbor kid to suit up in a hazmat suit, slide him under your car (which is up on jack-stands on a 20'x20' tarp), and have him bristle-brush every square inch with kerosene, repeatedly, till it shines like new. (Don't warn him in advance about the skin burns or he might not take you up on the offer). In fact I couldn't find such a kid, so I did it myself. That's NOT 'the easy way', tho. I took a 2nd place at Oktoberfest in '82, but to this day my skin tingles at the first whiff of light distillate petroleum. Good luck- Kevin Quote Link to post Share on other sites
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