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!!

 

[Wild Turkey]

My old NSX had a stainless SOS replacement coolant reservoir, which solved the problem of the OEM ones only lasting about 15 years or so, but it was a bit annoying to have to be guesstimating the coolant lever with whatever I could find for a dipstick.

Thus I was glad to see what I thought was an OEM reservoir on my '01. However, looking more closely as I was refilling the system, it is a completely opaque white, with no way to view the level. Perhaps it has been changed after the OEM one leaked? (Surprised the aftermarket would be jumping in with a product for such a low volume vehicle.) However, this one is virtually identical to the OEM sizewise, save lacking transparency and markings for MIN and MAX levels. Can anyone take a quick measurement on what the MIN and MAX levels are on the OEM reservoir so I can calibrate my dipstick?

 

[Honcho]

My old NSX had a SOS replacement coolant reservoir, which solved the problem of the OEM ones only lasting about 15 years or so, but it was a bit annoying to have to be guesstimating the coolant lever with whatever I could find for a dipstick.

Thus I was glad to see what I thought was an OEM reservoir on my '01. However, looking more closely as I was refilling the system, it is a completely opaque white, with no way to view the level. Perhaps it has been changed after the OEM one leaked? (Surprised the aftermarket would be jumping in with a product for such a low volume vehicle.) However, this one is virtually identical to the OEM sizewise, save lacking transparency and markings for MIN and MAX levels. Can anyone take a quick measurement on what the MIN and MAX levels are on the OEM reservoir so I can calibrate my dipstick?

Can you take a picture of it?

 

[Kaz-kzukNA1]

Most likely, you have the OEM tank but heat cycled and aged.
It’s famous for even the new OEM tank turning into opaque white within several months of installation.

In several countries, the driver is required to carry out pre-driving inspection including checking the coolant level.
Yet, it’s not easy to check the level once it turned into opaque white.

Therefore, one could argue it’s material failure but with such low production numbers, probably Honda didn’t spend the time re-designing it.

I normally just use the flashlight from the back.

Kaz

 

[Wild Turkey]

Pics:

Probably right Kaz. But it's so opaque even my flashlight from the back won't illuminate it. There is a line labelled MAX that I can see on the backside. Is the manufacturing seam line the minimum level? Wish I could tap between the new hoses I just installed with a clear hose as indicator. There must be some sort of T's and clear hose that could take the pressure. Has anyone done it?

 

[comtec]

Probably right Kaz. But it's so opaque even my flashlight from the back won't illuminate it. There is a line labelled MAX that I can see on the backside. Is the manufacturing seam line the minimum level? Wish I could tap between the new hoses I just installed with a clear hose as indicator. There must be some sort of T's and clear hose that could take the pressure. Has anyone done it?

Just below the seam is where the min level is marked. You should see the max and min on the right of tank behind the hoses in your second pic. I normally take off the cap and shine the flashlight down inside to make it viewable through the tank.

 

[Old Guy]

Thus I was glad to see what I thought was an OEM reservoir on my '01. However, looking more closely as I was refilling the system, it is a completely opaque white, with no way to view the level. Perhaps it has been changed after the OEM one leaked? (Surprised the aftermarket would be jumping in with a product for such a low volume vehicle.) However, this one is virtually identical to the OEM sizewise, save lacking transparency and markings for MIN and MAX levels.

Did you not source the replacement from Acura or a trusted vendor like Amayama because OEM tanks are still listed as available. I have a Dali aluminum round tank on my car and fabricated a dipstick for checking the level. Its a piece of 1/4" diameter plastic rod with a tape mark for the level. I don't know that the level is necessarily correct; but, I do know whether anything changes.

When I did my hose change I put the original tank back on the car to facilitate the coolant fill and bleeding process. As you note, the tank is pretty opaque. Like comtec, I had to use a very bright small 2 cell LED flashlight stuck into the opening for the pressure cap to see the level from the outside so you still need a 'tool' to check the level; however, at least I know the level is correct. Really hard to check the level with a hot engine / cap in place.

Not my tank; but, this photo shows the position of the min and max marking. As noted, min is about 1 cm below the seam and max is about 2-3 cm above the seam. I marked the level lines with a permanent sharpie to make checking things easier.



It does look like there are some tanks which are being sold as OEM out there which are missing the min and max markings.

 

[Wild Turkey]

Correction: "I was glad to see during my pre-purchase inspection..." I didn't change the reservoir. I had just got so used to looking down the spout of my old stainless unit in my 1995 that I'd been doing that since I bought the 2001, even though it had an OEM tank. While changing the hoses, I had to refill and bleed the system and I tried to view the coolant level and could not. Agree with Taz that it is just seems to have opacified somehow after only 25 years, but the MIN markings are difficult to discern so maybe it is an aftermarket copy.

 

[Honcho]

I'm late to the party here but yes, this is an OEM tank that has just "crustified" into an opaque plastic. You typically replace this when you do the hoses, but yours isn't leaking so no real reason to do it. Just keep an eye on it. On my 91 that had a similarly old tank, I found the bright flashlight into the fill cap worked the best like @comtec The plastic was too opaque to use the behind the tank flashlight trick. This is another part that I wish Honda had revised before the car was cancelled. The tanks on my Fords have been perfectly transparent and leak free in a high heat twin turbo environment. Even the GT-R tank held up way better than the NSX. So, the technology exists.

 

[Wild Turkey]

I can see the level using some tubing. I forget - is this Archimedes principle?

Actually, looks like there's an ap for it on my phone!

Problem solved. Thanks Mike! (I should have zoomed out a bit more on my photo to see your awesome coil guards.)

 

[britlude]

the OEM tanks all appear to crack on that seam... i think it's where there are the 2 mounting bolts on the left, on a metal bracket, the plastic tank can expand and contract as necessary, and the metal bracket doesn't, stressing the plastic until it fails....

top tip.. dont tighten the mounting bolt closest to the back of the car....

 

[comtec]

Problem solved. Thanks Mike! (Should have zoomed out a bit more on the photo to see your awesome coil guards.)

You're welcome. I have the rubber R cover so that's the only way I can check mine.