Timo Posted June 24, 2019 Report Share Posted June 24, 2019 As part of a engine coolant checkup, I'm in the process of changing both the drain tap on the engine block and the drain tap on the radiator. My question is how should I go about ensuring a good seal for these? 1. Engine block drain tap - should I use a sealant or a fibre washer. Hard to tell with the one I removed, fibre washer or some sort of sealant. Btw I'm changing it because the tap leaks. 2. Radiator drain tap - should I use ptfe tape or is there something else more suited? I'm changing like for like and the tap is the type with the bar which screws open the valve. The bar on the original spun without opening the valve hence the swap out.The new drain tap appears identical with tapered thread but only screws in 2 or 3 turns, whereas the original screwed quite a bit further. My approach is to use a sealant to provide seal and not over tighten. Appreciate any advice Thanks Tim Quote Link to post Share on other sites
Waldi Posted June 25, 2019 Report Share Posted June 25, 2019 Hi Timo, Welcome to the forum. I too used sealant. It is very important to remove all deposits from the thread in block and radiator first, I used steel round wire brushes for this (I have a set of many sizes, both brass, steel and “plastic”. If not properly removed, the tap will not go in fully. On the engine block tap I used a fibre washer, additional to the sealant. If you have an original engine tap, it is worth trying to get that working and tight again. I left it in hot water with some citric acid (normally used for water cooker and coffee machine in the kitchen) for some time, that worked ok. Waldi Quote Link to post Share on other sites
Kevo_6 Posted June 25, 2019 Report Share Posted June 25, 2019 Hi Tim I use liquid ptfe and concur with Waldi. This is the one I use and good for fuel too. https://www.toolstation.com/tru-blu-pipe-thread-sealant/p40236 Oh and make sure you get all the crud out inside the block use a bit of coat hanger, you’ll be surprised how much is in there, unless you’ve cleaned it out previously. Quote Link to post Share on other sites
jogger321 Posted June 25, 2019 Report Share Posted June 25, 2019 When my engine tap on the block started weeping I did buy a new replacement but chickened out fitting it as it was very tight. In the end I got my local engineering shop to tap the thread on the actual screw in tap and put a larger bolt in it with ptfe...and put the old one back in.. I'm getting better at working on these cars but still regard myself as a complete novice... But I really didn't want to strip or damage the thread on the engine block!! Quote Link to post Share on other sites
Z320 Posted June 25, 2019 Report Share Posted June 25, 2019 Hi, I use a 1/4" ball valve (with fibre washer) with nozzle on the engine, that workes lovely. see here Ciao, Marco Quote Link to post Share on other sites
Nigel Triumph Posted June 25, 2019 Report Share Posted June 25, 2019 I use PTFE plumber's tape on the threads of these plugs/taps, whichever are fitted. It seals fine and eases removal next time. I also fit a fibre washer under the head of the brass drain plug on the block. Belt and braces perhaps but it doesn't leak that way! Nigel Quote Link to post Share on other sites
jerrytr5 Posted June 25, 2019 Report Share Posted June 25, 2019 In my experience the drain taps are just a potential fail point. Replace both with blanking plugs and copper washers. The radiator one is pointless as you just need to release the bottom hose, the engine one will get blocked and you'll have to remove it anyway. Jerry Quote Link to post Share on other sites
DaveR Posted June 25, 2019 Report Share Posted June 25, 2019 A copper washer and silicon sealer on the threads. On the later TR6 engine they did away with the block tap and used a threaded plug. As for the rad I just remove the bottom hose as I find it is more effective when flushing out the system. Dave Quote Link to post Share on other sites
Timo Posted June 25, 2019 Author Report Share Posted June 25, 2019 Thanks for all the replies. I've checked for crud! There was a bit which I removed and the new tap screws into the block with no noticeable obstruction. Waldi - I will go for belt and braces option sealant and fibre washer, looks like a 1/2" x 3/4" x 1/16" is required. I must confess I knarled the original block tap when I removed with adjustable spanner. Must try harder! Kev - I couldn't find my ptfe tape last night so will give the liquid stuff a whirl. Tool station also do fibre washers so a one-stop shop should get me finishing the job. Lancia Beta Coupe very nice. A fiat twin cam is top my list for my second car. Marco, I like your solution but keeping an original look, well for now anyway. Dave, Jerry - I can see the logic in doing away with the taps as they are failure points. For the engine block I like being able to check that coolant can flow to the rear of the engine. If the new block tap plays up I'll consider changing to a plug. For the radiator I like the idea of a no mess drain approach. Tim Quote Link to post Share on other sites
Timo Posted June 25, 2019 Author Report Share Posted June 25, 2019 Thanks Nigel too. I'll grab a roll of ptfe tape in case I don't get on with the liquid stuff. Quote Link to post Share on other sites
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