I was driving and a big hose under my NA NSX blew. I was lucky because I already had a set of new OEM coolant hoses just in case but man was it a pain in the butt to do. I made a video to help anyone out if they run into this now common issue. -Driver's Therapy
Blew a coolant hose under the car so I made a video to help others
- Thread starter Driver's Therapy
- Start date
FYI I would run a compression test and a block gas test as a precaution. When the big hoses go, the heads usually warp.
I turned the car off right away when it blew. Is the big hose issue a symptom of something I am not understanding? Thank you for the help.
Were you above 5,000 rpm when it blew? The issue with the big hoses is they dump coolant so fast (especially at high rpm) that it is difficult to shut the car off fast enough to avoid engine damage. By the time you smell coolant and see the temp gauge pegged to the red, the engine has been running with no coolant for a while. With the smaller hoses like the oil cooler you have better odds.
The NSX engine is sensitive to heat stress due to the open deck layout- the volume of coolant around the sleeves acts as a heat sink. When that coolant disappears, it only takes a couple seconds to warp the heads and blow the head gaskets. The fix is to pull the heads and have them milled. This has happened to dozens of owners over the years, usually at the track and usually on the straight at high rpm. It happened to our own @mskrotzki going up the Eisenhower pass- he shut the car down but it was too late. He now has a shiny new SOS rebuilt engine.
That is why we always recommend a compression test and block gas test after a main hose blows. It can help you determine if you have a head warpage issue without the time and expense of pulling the heads. This is also why I stress over and over for owners to change their hoses- it's one of the few ways the otherwise reliable NSX can really go south fast.
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Thanks for posting. Now I'm reassured that paying to have all my hoses replaced a couple of months ago was absolutely the right move.
Smart man.
You are awesome, thank you for the heads up. I went and made sure my NSX is good, and it is. Looks like I turned it off fast enough.Were you above 5,000 rpm when it blew? The issue with the big hoses is they dump coolant so fast (especially at high rpm) that it is difficult to shut the car off fast enough to avoid engine damage. By the time you smell coolant and see the temp gauge pegged to the red, the engine has been running with no coolant for a while. With the smaller hoses like the oil cooler you have better odds.
The NSX engine is sensitive to heat stress due to the open deck layout- the volume of coolant around the sleeves acts as a heat sink. When that coolant disappears, it only takes a couple seconds to warp the heads and blow the head gaskets. The fix is to pull the heads and have them milled. This has happened to dozens of owners over the years, usually at the track and usually on the straight at high rpm. It happened to our own @mskrotzki going up the Eisenhower pass- he shut the car down but it was too late. He now has a shiny new SOS rebuilt engine.
That is why we always recommend a compression test and block gas test after a main hose blows. It can help you determine if you have a head warpage issue without the time and expense of pulling the heads. This is also why I stress over and over for owners to change their hoses- it's one of the few ways the otherwise reliable NSX can really go south fast.
thank you reading checking out the post.
I'm really glad your NSX is OK and it's very fortunate this cataclysmic event didn't necessitate a rebuild, especially with the continued motoring. Wishing you many safe motoring years in your NSX. Hopefully someone will benefit from your experience and change out their coolant hoses in time to avoid failure. Hopefully someone with a coolant leak will not follow this video and continue to sequentially refill (without bleeding!) and drive, 4 times?!? Is this so reckless, especially as being promoted by a "technician", that the video needs a recall/re-edit?
Maybe mention the capacity and how far 1 jug will go? Maybe add some video of an actual NSX hose being replaced? Maybe add some details on the bleed, which is quite a job?
Maybe mention the capacity and how far 1 jug will go? Maybe add some video of an actual NSX hose being replaced? Maybe add some details on the bleed, which is quite a job?
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Agree- you might want to post a follow up video. It would be helpful for owners to know how to do a compression test and block gas test.
Thank you for the concern and I appreciate you watching the video. I have decades of experience with overheating issues either with my own cars or on the racetrack. I made sure to keep my temps down and I live in a small town with little stop lights and a even grade, I was able to make it home with no issues by watching the temps.
I'm glad you were able to make it home safely. I did the same thing with my 1988 Accord in law school many years ago: filled at a gas station off their garden hose. For other owners, I would not recommend doing that with the NSX. Ever. The water pump flows 150L of coolant per minute at 6,000 rpm, or 2.5L per second. That means the water pump will empty the entire cooling system (16L) in about 6.4 seconds. You get a few more seconds at slower engine speeds, or with a smaller rupture (like on the heater or oil cooler lines). Adding a gallon of water gets you about 2 or 3 seconds of driving before the system is dry again. Even worse, all the air that gets sucked into the system must be purged before you can run the engine again, or you risk steam bubbles at the deck surface (air rises) that will destroy the head gasket and warp the heads. This happened to me at the 2012 NSXPO track event (heads were ok but gaskets were trashed), and that was with a fully filled coolant system letting in air.
When a big hose fails, the best thing to do is shut the car down and don't run it again until you have repaired the hose, filled the coolant and performed the complete bleed procedure to purge any air. Then, you should do the compression test and block gas test to make sure the head gaskets are intact. Your block gas fluid should look like this:
If it turns yellow, you must replace the head gaskets and likely have your heads milled.
When a big hose fails, the best thing to do is shut the car down and don't run it again until you have repaired the hose, filled the coolant and performed the complete bleed procedure to purge any air. Then, you should do the compression test and block gas test to make sure the head gaskets are intact. Your block gas fluid should look like this:
If it turns yellow, you must replace the head gaskets and likely have your heads milled.
that's pretty cool! I am reading about that tester right now. Thanks for the info.
I appreciate your perceived experience, but I remain concerned that this video does not identify how dangerous this is and that no one should follow this example with an NSX. I'm sure you know that the temperature sensor is only measuring the temperature at one location and that other temperatures can be much higher, dramatically so if the coolant is not fully present. Even if you got away with it, I think you need to add the best advice possible for viewers with lesser experience.
I see your point and I added and pinned a statement letting others know to not drive their car if they suspect a large leak. I never instructed or told anyone to do so, I told people what I did. Same as telling a story. I did NOT know I had a big coolant hose rupture, if so, I might have not driven down the road, but the car kept some coolant and made it safely down the road still. and runs perfectly.
I made a video about the information we discussed here:
Pretty interesting topic.
Most of my coolant hoses are looking in pretty decent condition, I've no idea when (if) they have been changed already and I don't see the point (nor the effort) of changing them all if not necessary.
But, what I've read here starts to make me stress out about the big hoses.
Can you please let me know which ones are concerned exactly?
I found some lists of all coolant hoses, but I don't see clearly which ones are the big ones or not.
I guess 17+18 on these schemas here, but maybe more? 9+10 ?
Thread '23 Coolant Hoses' https://www.nsxprime.com/threads/23-coolant-hoses.38807/
Most of my coolant hoses are looking in pretty decent condition, I've no idea when (if) they have been changed already and I don't see the point (nor the effort) of changing them all if not necessary.
But, what I've read here starts to make me stress out about the big hoses.
Can you please let me know which ones are concerned exactly?
I found some lists of all coolant hoses, but I don't see clearly which ones are the big ones or not.
I guess 17+18 on these schemas here, but maybe more? 9+10 ?
Thread '23 Coolant Hoses' https://www.nsxprime.com/threads/23-coolant-hoses.38807/
After reading this, now I’m getting nervous also. I had always just worried about timing belt failure destroying my engine, but it sounds like coolant hose failure will do the same. Is there a recommended time/mileage for mandatory coolant hose replacement similar to timing belt schedule??? Or is there some way to know or test for impending failure?
Depending on your weather condition, car use and parking conditions, it can be really different durability. I guess a good visual inspection is the best way to verify them, but as driver's therapy said in the video, it's very hard to inspect the big ones under the car in the tunnel, particularly if there's any wear/cracks in the top of them, against the tunnel, almost impossible to have a look here, or maybe with an endoscope camera.
My car has 120K miles and I rarely drive it hard, it is parked in the garage, and I live in dry climate. I think these hoses should be checked when possible. You have to remove a small plastic tray underneath them to see them.
My car is a 97 , bought it in 08 , changed all hoses in 09 . I cut all hoses open there was no degradation on any of them , my concern was hoses in engine compartment because they see most of the heat , everything good .
I have attached a .pdf with the list of all coolant hoses for my 2000 model year. The list includes diagrams showing the location of all the number referenced hoses for the model year 2000. Be aware that the list is year specific as things changed during the production run, particularly with the DBW throttle system.
There are 6 'big hoses' if big hose means the large diameter hose. All of the large diameter hoses are on the first diagram, parts # 9, 10, 11, 12, 17, and 18. On the second and third diagrams there are no large diameter hoses.
Anecdotal reports suggest that it is the three hoses at the engine bay that were the hoses most prone to failure on cars that saw track duty. This 'prone to failure' had been attributed to heat exposure from the engine. Those are hoses 11, 12 on the first diagram and 11 on the second diagram. That is not the failure reported by Driver's Therapy so no guarantees! The track car failures were likely heat accelerated failures. As the cars age heat accelerated failures may be less of an issue as a lot of the cars enter the 'just getting old phase of life'.
I think the rationale for just addressing the big hoses is two fold:
1. All the coolant hoses are exposed to the same cooling system pressure. The big hoses having a larger diameter are exposed to greater physical stress because of their larger surface area and as such may be more prone to rupture
2. The big hoses are the primary coolant circuit and rupture will dump coolant faster with less time to respond to a failure.
I think that is the rationale which may or may not be valid. If one of the hoses on the oil cooler fails it may not dump coolant as fast; but, you may also not notice the smaller cloud of steam so the outcome may be the same. Also, the oil cooler hoses can get exposed to oil which may accelerate deterioration.
I replaced all the hoses (except for two) on my 2000 this fall. None of the hoses showed any visible signs of deterioration; however, I live in a place where the ambient temperatures probably qualify as cooler. If you live in Arizona and like to zoom around in the dessert on 100 F days the under hood temperatures are probably way beyond what my car gets exposed to.
The two hoses I did not do on my car are the #6 heater valve inlet and #1 oil cooler inlet. I didn't do those because the clamp tangs on the heater hose were turned towards the back of the car and the whole thing was buried behind the EPS rack. In that case you can barely even see the clamp with the EPS rack in place. The same problem occurred on the oil cooler inlet hose where the release tangs were rotated to the back and the access was blocked by the intermediate shaft. I could not get at the clamp tangs with my articulated pliers and the flexible cable style hose clamp tool was always popping off the tangs (it was a rather poor quality tool). I had a limited amount of time to work on my car and I didn't want to be in a position where I had gotten the old hose off; but, couldn't get the new hose back on. At some point I will probably come back to make another run at those tow particular hoses.
I only confirmed by checking the part numbers for 2000; but, I think the part numbers are correct for any car that is equipped with the DBW throttle body which I think is 1996+.
I think the primary differences in the pre and post DBW are some of the small hoses that attach to the throttle body. I think the big hoses and the heater hoses are the same. My recollection was that all the French drivers were (mostly) driving on the right side of the road so the rest of the hoses are correct. If you purchased a JDM or UK market car designed for driving on the other side then there are a couple of the hoses up front that are incorrect.
I think the primary differences in the pre and post DBW are some of the small hoses that attach to the throttle body. I think the big hoses and the heater hoses are the same. My recollection was that all the French drivers were (mostly
) driving on the right side of the road so the rest of the hoses are correct. If you purchased a JDM or UK market car designed for driving on the other side then there are a couple of the hoses up front that are incorrect.
I think that way more engines were lost by blowing a hose than timing belt. Actually anybody broke OEM timing belt ?? It's hard to tell just by looking at those hoses. If you hear crunching when you squeeze then, than they are on the last leg. If you are not sure when they were replaced, than I would change them. That is what I do when I buy NSX. Hoses,TB,WP,clutch master and slave...
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