Lennym1984 Posted June 10, 2019 Report Share Posted June 10, 2019 Hi, My car appears to be losing a small amount of coolant over time and I'm having trouble finding the leak. The amount it is losing is not much, the light hasn't been triggered and I have had no overheating issues...but I still want to get to the bottom of it. My feeling is that it could be one of the radiators (the crossover pipes look fine, the water pump has less than 500 miles on it, and the expansion tank is newish and not leaking) but I also wonder whether it might be the coolant cap? I think mine is original (so 21 years old) and ends in 01. My understanding was that usually when the coolant cap fails, you can spot condensation in the boot. I have never had any signs of condensation and so I think this may discount that theory? Is this true or could this be my culprit (I really can't be bothered to remove the bumper again so am hoping for something easy) Link to comment Share on other sites More sharing options...
charlieboy2608 Posted June 10, 2019 Report Share Posted June 10, 2019 Apart from checking the FREE obvious bits which you've alreadychecked I'd probably go for the cheapest part 1st...ie,the coolant cap Link to comment Share on other sites More sharing options...
GmanB Posted June 10, 2019 Report Share Posted June 10, 2019 When my coolant cap failed, it emptied all the coolant within minutes. Boot was bone dry. Quite worrying at the time, but pressure testing for over an hour showed nothing wrong with rads, pipes and temps. Logic dictated it was the rad cap and was replaced, 5k miles later it's good as gold. Just ensure you get the correct pressure cap, I believe they changed the pressure on them at some point on the 986. Link to comment Share on other sites More sharing options...
the baron Posted June 10, 2019 Report Share Posted June 10, 2019 Coolant cap should end in 04 if not replace, next remove boot carpet which is attached to a piece of plywood, look for signs of coolant leak around expansion tank on boot floor, it’s either of those two things, good luck Link to comment Share on other sites More sharing options...
Lennym1984 Posted June 10, 2019 Author Report Share Posted June 10, 2019 8 minutes ago, the baron said: Coolant cap should end in 04 if not replace, next remove boot carpet which is attached to a piece of plywood, look for signs of coolant leak around expansion tank on boot floor, it’s either of those two things, good luck I've checked the expansion tank (in the way you mention) and there is no coolant visible so hopefully it'll be the cap. If not, I'll be removing the bumper (I need to respray the stonechips at some point anyway,) Link to comment Share on other sites More sharing options...
edc Posted June 10, 2019 Report Share Posted June 10, 2019 The bleeder valve o rings can also go. But you would normally see condensation in that boot area. Link to comment Share on other sites More sharing options...
charlieboy2608 Posted June 10, 2019 Report Share Posted June 10, 2019 I've also seen written on here that if you dont have a new expansion tank (you said newish so not sure if its brand new or from a donor vehicle) that a new cap which has greater pressure can cause an older tank to leak...... Link to comment Share on other sites More sharing options...
Boxob Posted June 10, 2019 Report Share Posted June 10, 2019 You can pressure test the system. I borrowed a kit from my local friendly garage. The kit replaces the blue cap with a cap with a valve to which a hand pump is attached. A few pumps and I started to hear a hiss - the o/s rad had been stoned. Leak revealed! My guess is that the leak was so slight that during the normal operating temperature the coolant was evaporating. Perhaps you have the same issue. Link to comment Share on other sites More sharing options...
Menoporsche Posted June 10, 2019 Report Share Posted June 10, 2019 24 minutes ago, Boxob said: A few pumps and I started to hear a hiss - the o/s rad had been stoned. That’s, like, totally rad, man. Link to comment Share on other sites More sharing options...
Boxob Posted June 10, 2019 Report Share Posted June 10, 2019 Just now, Menoporsche said: That’s, like, totally rad, man. I'll set them up.... Link to comment Share on other sites More sharing options...
Sonic909 Posted June 11, 2019 Report Share Posted June 11, 2019 Mine loses about 300ml a year/3000 Miles mystery. Link to comment Share on other sites More sharing options...
½cwt Posted June 11, 2019 Report Share Posted June 11, 2019 Took me a long time to find my slight coolant leak. Traced it tot eh end of one of the cross over hoses behind the front left wheel. I changed the hose as I had a replacement but as I took off the spring clamps I found one of the two metal bands was fractured. The old hose was still flexible and had not gone soft so was probably OK. Found this on the front of the other hose in the same position. Turns out there was a slight leak due to loss of clamping pressure. Downside is that to check you have to remove them and risk causing a fracture when doing so. I opted to go with jubilee type replacements so I coud undo and loop them over the pipe without breaking the water line again after refilling the system after I found another one weeping. Link to comment Share on other sites More sharing options...
Lennym1984 Posted June 11, 2019 Author Report Share Posted June 11, 2019 2 hours ago, ½cwt said: Took me a long time to find my slight coolant leak. Traced it tot eh end of one of the cross over hoses behind the front left wheel. I changed the hose as I had a replacement but as I took off the spring clamps I found one of the two metal bands was fractured. The old hose was still flexible and had not gone soft so was probably OK. Found this on the front of the other hose in the same position. Turns out there was a slight leak due to loss of clamping pressure. Downside is that to check you have to remove them and risk causing a fracture when doing so. I opted to go with jubilee type replacements so I coud undo and loop them over the pipe without breaking the water line again after refilling the system after I found another one weeping. Was there any visible sign of the leak (ie. Crusty powder)? Mine all look fine externally Link to comment Share on other sites More sharing options...
the baron Posted June 11, 2019 Report Share Posted June 11, 2019 My money is still on either the cap or the expansion tank Link to comment Share on other sites More sharing options...
Lennym1984 Posted June 11, 2019 Author Report Share Posted June 11, 2019 50 minutes ago, the baron said: My money is still on either the cap or the expansion tank I checked the boot floor again last night (the plywood makes it a pain) so I hope that you are right about the cap Link to comment Share on other sites More sharing options...
the baron Posted June 11, 2019 Report Share Posted June 11, 2019 1 hour ago, Lennym1984 said: I checked the boot floor again last night (the plywood makes it a pain) so I hope that you are right about the cap Hopefully it is just the cap, under the plywood you can see under the expansion tank is there any signs at all of any coolant, either around the pipes or under the plastic chamber, mine didn’t show any signs as it tended to evaporate as it gets quite hot in there so sometimes a slow leek won’t be obvious. Link to comment Share on other sites More sharing options...
½cwt Posted June 11, 2019 Report Share Posted June 11, 2019 11 hours ago, Lennym1984 said: Was there any visible sign of the leak (ie. Crusty powder)? Mine all look fine externally There was dampness on the underbody of the car (made the car look deceptively clean underneath) and a very occasional drip. As it was ongoing there was no drying up so no residue or powder. Link to comment Share on other sites More sharing options...
Lennym1984 Posted June 15, 2019 Author Report Share Posted June 15, 2019 So initial reports would suggest that a new coolant cap has fixed the problem. I had a look at the old cap and it would appear that the valve was getting stuck. Thanks for the advice as always Link to comment Share on other sites More sharing options...
GmanB Posted June 16, 2019 Report Share Posted June 16, 2019 Brilliant news and a cheap fix 👍 Link to comment Share on other sites More sharing options...
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