Coolant tank expansion leak

[favetita]

Need help with the old leaking coolant tank expansion. Looks like leak coming from the seams and leaking down to the bottom hose, trickling down more hoses ending on the garage floor. There are about a dozen small spots the following day after coming home from my Sunday drives. Needs changing before it gets worse. OEM lasted for 20 years, so thinking of going the OEM new (old) stock route. Aside from expansion tank, coolant and upper and lower hoses, what else is needed? Any tips for a problem free remove and install? Will probably look for a mechanic to do this one but will pass along words of wisdom, as I am not mechanically inclined to do this myself. Thanks in advance for any help.

 

[Old Guy]

Removal and replacement of the expansion tank is not difficult. You should be able to accomplish it in 1 hour if you clamp the hoses to prevent loss of coolant from the rest of the system.

Aside from expansion tank, coolant and upper and lower hoses, what else is needed? .

Upper and lower hoses - are you talking about the two hoses that connect to the expansion tank? Removal of those hoses precludes clamping to reduce coolant loss. Unless you damage the hoses during R&R of the tank, those hoses are probably the least stressed in the cooling system. Depending on the car, you might want to consider a complete cooling hose replacement if the hoses are > 20 years. If you just replace the tank, a new cap to go with the tank might be a good idea. If the coolant is over 3 years old then a complete coolant flush would also be a good idea.

If you have a mechanic do the work, a pressure test of the cooling system would be a good idea to confirm that the expansion tank is the only thing that is leaking.

 

[Honcho]

Need help with the old leaking coolant tank expansion. Looks like leak coming from the seams and leaking down to the bottom hose, trickling down more hoses ending on the garage floor. There are about a dozen small spots the following day after coming home from my Sunday drives. Needs changing before it gets worse. OEM lasted for 20 years, so thinking of going the OEM new (old) stock route. Aside from expansion tank, coolant and upper and lower hoses, what else is needed? Any tips for a problem free remove and install? Will probably look for a mechanic to do this one but will pass along words of wisdom, as I am not mechanically inclined to do this myself. Thanks in advance for any help.

Definitely replace with another OEM tank. I did this job once in the parking lot of my apartment complex- didn't spill. Here's the trick: the upper hose is easily detached, since there should be no coolant at that level. Before detaching the lower hose, remove the tank bolts and tilt the tank backwards, so there is no coolant at the lower hose nipple. Carefully detach the lower hose and make sure you keep it upright and pointing up- it is full of coolant and will dump a bunch of it all over your transmission case if you tilt it low. I used one of those long twistie ties from the supermarket to secure it to something nearby so that I had free hands to work on the new tank. Then, attach the lower hose to the new tank first. After that, you can manipulate the hose/tank without spilling as you re-mount it and install the upper hose. Please make sure not to over-tighten the mounting bolts- doing so can result in premature cracks. I gently snug them and then back them off just a smidge. Have had good luck with this method.

Good advice to replace the rest of the hoses if they are original- a burst hose on the NSX can be a new-engine level mistake and it has happened. Definitely go with a new cap. SOS sells a good one.

 

[favetita]

Removal and replacement of the expansion tank is not difficult. You should be able to accomplish it in 1 hour if you clamp the hoses to prevent loss of coolant from the rest of the system.



Upper and lower hoses - are you talking about the two hoses that connect to the expansion tank? Removal of those hoses precludes clamping to reduce coolant loss. Unless you damage the hoses during R&R of the tank, those hoses are probably the least stressed in the cooling system. Depending on the car, you might want to consider a complete cooling hose replacement if the hoses are > 20 years. If you just replace the tank, a new cap to go with the tank might be a good idea. If the coolant is over 3 years old then a complete coolant flush would also be a good idea.

If you have a mechanic do the work, a pressure test of the cooling system would be a good idea to confirm that the expansion tank is the only thing that is leaking.

Thank you for the pressure test advise and coolant flush advice. Last coolant flush was 10 years ago, not a big deal as this garage queen is only driven about 1k miles a year :smile:

 

[favetita]

Definitely replace with another OEM tank. I did this job once in the parking lot of my apartment complex- didn't spill. Here's the trick: the upper hose is easily detached, since there should be no coolant at that level. Before detaching the lower hose, remove the tank bolts and tilt the tank backwards, so there is no coolant at the lower hose nipple. Carefully detach the lower hose and make sure you keep it upright and pointing up- it is full of coolant and will dump a bunch of it all over your transmission case if you tilt it low. I used one of those long twistie ties from the supermarket to secure it to something nearby so that I had free hands to work on the new tank. Then, attach the lower hose to the new tank first. After that, you can manipulate the hose/tank without spilling as you re-mount it and install the upper hose. Please make sure not to over-tighten the mounting bolts- doing so can result in premature cracks. I gently snug them and then back them off just a smidge. Have had good luck with this method.

Good advice to replace the rest of the hoses if they are original- a burst hose on the NSX can be a new-engine level mistake and it has happened. Definitely go with a new cap. SOS sells a good one.

No need to spend money then on a more expensive aftermarket expansion tank. Was looking into one but will take your practical advise on going OEM. Just to get an idea, how many coolant containers do I need for a coolant flush? Will do complete flush after this one is addressed...need to buy the 20 or so OEM hoses. Thanks for the tip.

 

[JohnWayne]

Thank you for the pressure test advise and coolant flush advice. Last coolant flush was 10 years ago, not a big deal as this garage queen is only driven about 1k miles a year :smile:

If the hoses were done over 10 years ago then I echo what Honcho said. Replace all the coolant hoses. Mileage does not matter.

 

[favetita]

Update: Thank you for all your advice I was able to replace leaking expansion tank. See attached pic where leak was coming from. I aspirated coolant using a laboratory transfer pipette ( that took a while but was excellent advice.) There was minimal spillage once I was able to take the bottom hose off.... with much difficulty but finally came off. Once the new tank was on, I poured coolant but exceeded max line by half an inch. I made the mistake of trying to re-use the OEM reservoir cap. I warmed up for about 10-15minutes until temp gauge was where it usually sits, right at the 3 mark. All looked good, no leaks from top and bottom hose and coolant level stayed where it was the whole time so i called it a night.

Morning came, before leaving for work I went to the garage to check for leaks and was shocked to find a puddle of coolant past the rear driver side tire. I checked underneathand and was thankful to see that was all of the coolant tht leaked. I popped open the hatch and saw both hoses attached where they should be, no leaks from te cap, top and bottom hose, with coolant level now sitting perfectly under the max line. Coolant on the floor was the half an inch excess that spilled from the overflow hose. That's when I remembered the advice not to reuse the OEM cap because of size discrepancy. A few days later, I replaced the cap with the Sankei cap from SOS. Fifteen minutes warm up, and after sitting overnight, NO LEAKS!!

I drove trhis afternoon for 25 miles with a few aggressive pulls up to 6K on third, all throughout my drive the temp gauge where it usually sits at the 3 mark the whole drive. So happy.
Looking ahead, I will be replacing all hoses along with the TB/WP work. I will need a recommendation where to get this done. I am an hour noth of SF and prefer to have this done in the north bay and not have to drive furhter down south.

Thanks again for helping me out. You all are the best!!