The content in this Wiki page was extracted from over a dozen threads on the topic with significant content from Prime user: slightlyevil, Drew, and Slingshot but also with knowledgeable comments from Larry Bastanza and other experts. This is a job which can be tackled in a typical garage and a typical time is 6-8 hours (not including bleed time) if this is the first time you’ve done it, however many have expressed frustration getting at certain hoses; fighting with the clamps; etc. Total cost of the hoses is reported to be about $300 plus $700-900 for labor to have a dealer install them. Replacement of the oil cooler hoses separately is estimated at about 2 hours. Numerous people have recommended having the hoses replaced at the same time as the timing belt/water pump change which may save some labor costs. If doing just the oil cooler hoses, it is recommended that it be done at the same time as an oil change.
List of All Hoses
|Hose#||Part#||Part Description||Sample Cost|
|1||79728-SL0-A00||HOSE, WATER INLET (ENGINE)||15.95|
|2||79725-SL0-A00||HOSE, WATER OUTLET(HEATER)||6.86|
|3||79722-SL0-A00||HOSE, WATER INLET (HEATER)||5.18|
|4||79721-SL0-A00||HOSE, WATER INLET (WATER VALVE)||15.71|
|5 *||19518-PR7-A00||HOSE, WATER MIDDLE (UPPER)||21.98|
|6||19522-PR7-A00 (91-94); 19522-PR7-J001 (95-96); 19522-PR7-J021 (97+);||HOSE A, BYPASS||3.18|
|7||19424-PR7-A00||HOSE B, OIL COOLER OUTLET||8.90|
|8||19423-PR7-A00||HOSE A, OIL COOLER OUTLET||5.48|
|9||19422-PR7-A01||HOSE, OIL COOLER INLET||3.53|
|10 *||19506-PR7-A01||HOSE, RR. WATER (LOWER)(WHITE PAINTED)||16.70|
|11 *||19502-PR7-A00 (91-96); 19502-PR7-A01 (97+);||HOSE, FR. WATER (LOWER)(WHITE PAINTED)||24.08|
|12 *||19501-PR7-A00 (91-96); 19501-PR7-A01 (97+);||HOSE, FR. WATER (UPPER)(WHITE PAINTED)||16.70|
|13 *||19507-PR7-A01||HOSE, RR. WATER (UPPER)(YELLOW PAINTED)||16.70|
|14||19526-PR7-A00||HOSE E, BYPASS||4.05|
|15 *||19519-PR7-A00||HOSE, WATER MIDDLE (LOWER)||24.73|
|16||79727-SL0-A00||HOSE B, WATER JOINT||13.64|
|17||79726-SL0-A00||HOSE A, WATER JOINT||8.51|
|18||19524-PR7-A00 (91-96); 19524-PR7-A01 (97+);||HOSE C, BYPASS||3.38 *|
|19||19523-PR7-A00 (91-94 only)||HOSE B, BYPASS||4.25 *|
|20||19103-PR7-A00||HOSE EXPANSION (UPPER)||6.00|
|21||19104-PR7-A00||HOSE EXPANSION (LOWER)||6.00|
For automatics, add one of each of the following (these are for ’91s .. doublecheck for other years)
|Hose#||Part#||Part Description||Sample Cost|
|19429-PR7-A10||Hose, Cooler Inlet (ATF) 1991 NSX||11.08|
|19430-PR7-A10||Hose, Cooler Outlet (ATF) 1991 NSX||8.34|
For other miscellaneous parts you’ll probably need
|Part#||Part Description||Sample Cost|
|90042-PR7-A00||Coated bolts for oil filter housing (need 2)||2.10|
|91318-PY3-000||Figure 8 Oil Ring oil cooler gasket||7.00|
|19012-PV0-005||Radiator plug o-rings (need 2)||1.40|
|90471-580-000||Washer (8mm) (need 2)||1.08|
|90401-PE2-003||Washer, sealing (10mm) (need 2)||1.50|
|19300-PR7-A01||Thermostat (Nippon thermostat)||24.43||19515-PH4-600||Pressure cap, sealing (7.3mm)||2.68|
For pictures of the actual hoses, Prime user:UnhuZ provided this great summary post: http://www.nsxprime.com/forum/showpost.php?p=1413644&postcount=12
Note: the hoses in column one with an asterisk are the ones often referred to as “the big six” which can be bought as a set and are the ones most likely to fail. Automatic cars have a couple of extra hoses which are not listed here. The last item in the list is not a hose but rather an oil ring gasket for the oil cooler when it is removed to replace the hoses going to it. If you are doing the oil cooler hoses (highly recommended due to the heat), it is advisable to get an oil filter and do an oil change at the same time. Other than your Acura dealer, hoses can also be obtained through Science Of Speed here or Dali Racing here
Warning: Prime user: slightlyevil reported that the ‘standard hose replacement kit’ from SOS doesn’t include two key crush washers for the two drain plugs under the car. Order new crush washers for these two bolts when you order your pipes! There are two to replace and the part number is 90471-580-000 (8mm crush washer)
Various Coolant Hose Diagrams
The first diagram and list of hoses is referred to by Acura as the Parts Detail-Diagram For WATER VALVE
In the above diagram, #10 is under the car in the tunnel and #11 is in the engine bay under the coolant tank. Note that there are three pipes under the car, and in addition to
19518-PR7-A00 and 19519-PR7-A00 (18 and 17 in the following diagram) is hose #10 from the above diagram.
The following diagram focuses on some of the smaller hoses, especially the ones connected to the oil cooler
In the above diagram there are TWO hoses, #17 and #18. Also in the tunnel is #10, since that hose brings the water to the water valve for the heater core. There are another two hoses #11 and #12 in the above drawing and they are under the coolant tank ALONG WITH #11 discusses in the first diagram. So water comes from the block, through #11 in the top diagram, through #10 and into the water valve. #11 and #12 and #17 and #18 carry coolant to/from the radiator, #11/12 under the coolant tank, #17/18 in the tunnel. So there are THREE coolant lines that run front to back in the tunnel.
Tip: A lot of the coolant hoses around and to the throttle body/water pump are shown in the “Oil Cooler Hose” diagram (above) in the official Acura parts diagras like this one.
Not every hose looks exactly like the diagram. Sometimes the diagram will illustrate a hose as being longer than it actually is so the ends will line up with the hard lines or in the diagram. Sometimes the hose will even be a different shape! (I only ran into this once…a hose that was pictured as straight actually had a significant bend in it.
Note: the new hoses have a mark, an arrowhead or (a white or yellow dot on one end to orient them. (yellow on only one hose, the middle one in the engine bay IIRC, so you cannot mix the two up)), that indicates which end faces toward the engine. Some of the hoses are so subtly shaped that it’s tough to tell at first glance which way they go on, so referring to this mark can be helpful in confirming you have it right.
Draining the System
Here is a Wiki writeup on draining coolant from the system
Prime user: Larry Bastanza also commented “Using the block drains will get you pretty close. However they are clogged 1/2 of the time, especially on cars that have not had coolant changes in a while. So if you open them up and they do not flow, remove the outer piece, then use a pick or a short piece of wire hanger to unclog them. Remember to keep your face out of the way. Also drain the radiator completely, and open the two drains in the tunnel. The service manual has a good description/pics of this”
Removing Existing Hoses
Tools Required: There are no special tools required other than a set of strong fingers; sharp razor blade tools; a shop light; basic set of Craftsman pliers; and assorted ViseGrips. If you remove the oil filter base you’ll need a torque wrench that does 16 ft/lb; the figure 8 gasket between the oil cooler and block; and new bolts (2 short; 1 long) to reattach the cooler to the engine block. In addition, as was noted above, don’t forget the 2 x 8mm crush washers (90471-580-000) for the drains located on the “rear water pipe”; the 1 crush washer for the bleed bolt also located on the rear water pipes; and the 1 x bleed cap, located in front of the heater core on near the spare tire. It is also advisable to have 2x Radiator Plug O-rings, 19012-PV0-005
Besides long nose needle nose pliers (straight and bent), it was also suggested that having a set of pliers similiar to the following picture would be especially good for removing the smaller hoses Hose pliers2.png
Assuming the existing hoses have been on your car for 10+ years, removing them is going to be a challenge. The small hoses in the engine compartment are relatively easy. Don’t be shy about pulling parts off if they are in the way. Four bolts, a couple of connectors and some coolant hoses will get the throttle body out of the way. Ditto for that vacuum hose distribution bracket that is on top of the throttle body. People recommend only taking one hose off at a time and replacing it….makes positioning the new hose correctly a snap. The nipples are so closely spaced in a couple of areas it would be very easy to mix them up. The engine side of the all main larger hoses requires that you remove all of them and then put them back sequentially. They are buried under each other. Make sure you remove the air filter assembly, coolant tank and some strongly suggest dismounting the fuse box (if you do: detach the negative of the battery first!). If you have a good mechanical memory it shouldn’t be a problem. Just keep the parts diagrams handy. But if you tend to forget how things were arranged, take pics as you go. You won’t really have any problem getting each hose on the right hard lines or reconnecting the various electrical connections you have to unplug. But it isn’t that hard to mount a hose backwards. Or you might find a hose is not oriented correctly and you have to unclamp it to straighten it out and other stuff you have already reinstalled is in the way.
Due to the location of some of the pipes the old ‘push the hose into the fitting’ method does not really work to break the seal. You will likely have to wind up cutting the vast majority of pipes off the fittings and if you’re good with a blade I would recommend this because it saves so much time/hassle. However you have to be VERY careful when doing this not to cut into the fitting. Use a very sharp blade (both hands!), and cut lightly lengthwise multiple times down the pipe where it meets the nozzle, you don’t want to go the whole way through the rubber in the area it is over the fitting because you don’t want to scar the fitting. Once the blade is beyond the fitting and just on the hose area, push it the whole way through the hose. Now stick your finger in there and slowly pry it apart, peeling it back over the nozzle. If it’s not peeling you probably haven’t cut far enough in to the rubber over the nozzle area, so again carefully use the blade until it goes. If you DO manage to cut into the nozzle a tiny bit (you should only have scored it very lightly anyways) you can use some VERY VERY fine sand paper and smooth that area out, but remember it’s aluminum and easy to create a flat spot even with sandpaper very quickly. Just take your time and go slow. Do not touch the nipples with any thing metal, you’ll gouge them, although one owner suggested slipping a metal shim (like the old points/plugs thickness gauge) between the hose and the pipe to protect it from the blade.
While taking apart the engine bay (coolant tank, fuse box, intake box, throttle body) to get the three main pipes was not that hard I DID have problems with the throttle cable on the throttle body. I did not want to loosen the throttle cable, and did not want to kink/bend it either. I found the easiest way to get the throttle cable off the throttle body linkage was to remove the TB with the cable attached, flip it upside down to relieve the tension on the cable, then just remove the cable (it’s a bit odd if you’ve never done a door lock cable or throttle cable before, but look closely and you’ll see how it slides out of the notch on the inside of the linkage and then the cable end comes out of the linkage.) Putting the cable back on, I managed to do it with the throttle body bolted back in place, but I needed a second set of hands holding the throttle open so I could get enough slack in the cable line. Just take your time and study the way the cable has to wrap the linkage so you ensure you don’t kink/stretch/bend the line and you will be fine. This procedure will be different for TBW cares I assume, so I cannot speak to those.
Some people advise getting some decent multiple size pliers and grab the rubber that’s connected to the pipe/pipes and turn it. You only have to turn it half an inch to break the seal. With this method it may save you a finger as its hard to get into some of those tight spots and after the blade slides off the pipe there goes parts of your finger or arm what ever the blade takes with it. However, this approach should be used with caution because the fittings are surprisingly soft aluminum and you could easily bend/dimple/crush a fitting (big or small) simply by pulling that hard on a hose even at a slight angle. Prime user: Russ advised “I used three long-reach (14″) needle nose pliers – straight, 45 and 90 degree offsets and one pair of regular pliers. I also found in some cases you can rotate a clamp to a more advantageous position by pressing on the single tab in the direction in which it relieves tension on the hose. This makes it easier to get a grip on the tab when it’s just out of reach.”
Larry B also advises that a heat gun can be very effective in freeing up stuck hoses as well as for installing the new ones later.
Some of the clamps are very difficult to grab with pliers. A wide set of pliers may be an asset. Try grabbing some of the clips at a 30 degree angle to maximize the width, but if the clamp moves just a tiny bit it will spring across the floor or hide somewhere in the car. Use mechanic gloves, Sears sells these too for $20. They’ll keep your finger nails clean and prevent cuts that are going to otherwise occur doing this job.
Prime user: sers also posted some pictures of his coolant hose experiences here: http://www.nsxprime.com/forum/showthread.php?t=162513&highlight=cooler+hoses
Installing the New Hoses
Warning – do not use any petroleum-based lubricant (eg. WD-40) when re-installing hoses as it will attack the rubber hoses and ruin them. Use only silicone-based spray lubricants or silicone-based o-ring grease that can be obtained from swimming pool suppliers.
In addition to liberal use of silicone lubricant, others have suggested using a heat gun to soften the pipe. You have about 15 seconds before the hose sets and becomes difficult to turn or remove. Make sure the installed hose is relaxed in its position, you do not want any twisting. If possible stage the clamps on the hose, but not on the receiving end. Experience states that this is much easier to work with. Some clamps are easier to deal with if you can keep open in a Vise Grip, install the hose, place the clamp and then release. The two piece clamps are rather difficult to deal with, very rigid and they have three “prongs” to grab at the same time. If you get frustrated with these, people have suggested using your basic auto part screw clamp: these are used on the heater hose connections. However, others have had the screw type claws loosen and/or cut into the hose so use at your own risk. Before you slide it a hose on, make damn well sure the hose clamps are in the right position, and turned to the point you can get a good grip on them with some pliers to crimp them for installation.
Larry B also notes: “In regard to orientation of the hoses there is a colored dot on one end of each large hose, one yellow and one white. The colored dot should be on the engine side.”
Oil Cooler Hoses
For the oil cooler hoses, the recommendation is to remove the right rear tire and then the oil filter base/pedestal. The clearance is very tight around the small hose and the rear clamp is extremely difficult to grab. So while it may be possible to remove (cut) the hose, it would be impossible to reinstall. The base is secured by three bolts and a double o-ring like gasket. It doesn’t make much of a mess and it is easy to remove. The manual states to replace the three bolts and the gasket but the long bolt can be re-used. The shorter bolts (90042-PR7-A00) have the special sealant on them to keep them tight but you don’t need new bolts if you are able to just coat the threads with Hondabond HT before reinstalling. Larry B advises “do one hose at a time so the oil cooler/oil filter assembly is not dangling by the oil pressure sender wire. Another trick I can give you is to remove the heat shield from the CV inboard joint. It will make access to the smaller hose easier but not easy.” Prime user: sers concurred and said “removing the CV boot shield is a must, in my opinion (this in fact was the hardest part for me as I found one of the bolts was quite difficult to get to). I used long needle nosed pliers to get at the clamps and a very sharp blade to cut the hoses.” If you are just doing the hoses on the oil cooler, you will probably need about 4 gallons of replacement coolant since it is at the lowest point in the system. Raising the rear of the car higher than the front may reduce this to 2 gallons. Also, keep the water valve for the heater core closed when you drain, but open it before you fill. Prime user: sers provided the attached pictures and said “I found the trickiest part was getting at the top bolt of the CV joint shield (not shown)”. He also offered “Just make sure you stretch the mouth of the new hoses and use lots of water based lube when reapllying the hoses”.
Bleeding the System
Warning – do not drive the car until you have bled air out of the system.
Bleeding the car seemed daunting after reading the service manual PDF (which if you don’t have it, you need it, go download it here on prime it’s absolutely priceless). However, the only thing I found missing from the ‘method’ explained in the manual was that you REALLY DO need to elevate the rear of the car. I put mine about 1ft up on jackstands at the rear jackpoints and it helped fix the airbubble issue I was having. An alternative would be to take advantage of a steep driveway. With the car flat (as I assume an Acura tech would do it?) I was getting an airbubble in the rad and in the heater core, even with the core opened. Jacking the rear of the car up completely fixed this issue. I repeated the bleed procedure twice, yes you get coolant on the engine/floor/spare tire bracket – but it’s easy to clean up so just do it.
Older Acura vehicles typically use the green antifreeze solution while newer vehicles come equipped with the blue coolant. Coolants with silicates in them are known to shorten the life of water pump gaskets. Type 2 (long life) coolant is generally recommended.
What is the approximate cost for hoses and labor? – According to a post by Dtrigg, “the cost of the hoses is around $300, and the labor to remove and reinstall all of the hoses is around $900”
When should the hoses be replaced? – Real world experience is all over the place (including some as long as 17 years) but one piece of advice is that it may be cheaper to have them done when you’re having the TB/WP done. The downside of not having them done is that you could be left stranded in a bad place and, worse yet, if one bursts, the engine could quickly overheat and you don’t recognize it quickly enough, engine damage could result. Some people have said that heat and movement will accelerate failures so if your car has been tracked, you may want to replace them sooner rather than later.
Once you drain the coolant from the radiator, 2 lower pipes and 2 engine banks, you’ll need 12 L of coolant. The overflow tank holds 2L, does that mean we’ll need to “refill” the tank 6 times until we get the coolant all the way back into the radiator and entire system? – If you only drain it without removing the hoses then yes, 12l is about correct. If you change all hoses, it’s more like 15l