1992 New to me, coolant leak

[AdmiralCrunch]

So I just bought my first NSX, a 1992 NA1, mostly stock. Just had it delivered and upon pulling off the trailer noticed a small bit of coolant on the floor of the trailer. As I'm not an expert on things NSX (yet), I'm not certain but the coolant felt thicker than what I'm used to in modern cars. I'm used to coolant that is near the viscosity of water, but this was a little thicker.

Car has 89k miles on it and a SoS coolant tank. Rest of the cooling system is stock. As soon as I see thick coolant, my mind immediately jumps to oil in the system, possible head gasket issue. Hope that's not the case right out of the gate. Any insight would be appreciated!

 

[docjohn]

was the coolant from the rear of the car?

 

[AdmiralCrunch]

Looks to be coming from the upper part of the driver's side right under the throttle body somewhere. I didn't have a ton of time to check in detail and hope to get it up on a lift tomorrow for a deeper dive. Was more curious on coolant viscosity. My mind always immediately goes to worst case scenarios.

The car also hasn't been driven but like 3k miles over the past decade, so I have no clue when the coolant system was last checked.

 

[Hass]

There are radiator small hoses around the throttle body, there’s one actually on the throttle body.

 

[Hass]

Coolant leak under the throttle body

Hello Prime, I just took delivery of an NSX on Sunday. Haven't really driven it besides within the neighborhood, No tags/registration yet. Everything about the car is perfect. But last night when I moved the car out the garage I noticed a small puddle of coolant. I checked the engine and...

www.nsxprime.com

 

[Old Guy]

Correctly mixed coolant is definitely more viscous than water. If the coolant remains 'transparent' you probably do not have oil in the coolant. Oil mixed in with the coolant usually forms an emulsion. If you have enough coolant pooled in a spot you can shine a light on it to see if you get that 'oil film on water' that leads to multiple color reflection associated with thin films.

With an all aluminum engine it is best not to mess around with potential cooling system leaks. I would be inclined to get a coolant system pressure tester. Failure to maintain pressure will confirm a leak and with the cooling system pressurized you will probably be able to spot the source of the leak. The thermostat housing is right in that same general area as the throttle body so there are a lot of hose connections and gasket surfaces that can develop leaks with age.

 

[AdmiralCrunch]

Correctly mixed coolant is definitely more viscous than water. If the coolant remains 'transparent' you probably do not have oil in the coolant. Oil mixed in with the coolant usually forms an emulsion. If you have enough coolant pooled in a spot you can shine a light on it to see if you get that 'oil film on water' that leads to multiple color reflection associated with thin films.

With an all aluminum engine it is best not to mess around with potential cooling system leaks. I would be inclined to get a coolant system pressure tester. Failure to maintain pressure will confirm a leak and with the cooling system pressurized you will probably be able to spot the source of the leak. The thermostat housing is right in that same general area as the throttle body so there are a lot of hose connections and gasket surfaces that can develop leaks with age.

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Thank you very much for the info! I have read the cooling systems in these cars are a bit more complex. Good to know on the viscosity too. The spots on the trailer floor were still a clear bright green color, which I was hoping was a good sign.

Getting the car up on a lift here shortly to investigate further. I do suspect the thermostat is probably in dire need of replacement since it's been sitting with little use for so long.

Fingers crossed no head gasket issues!

 

[Old Guy]

Getting under the car to look for stuff is likely not going to be very useful in confirming the location of the leak. If the leak is around the throttle body or thermostat housing area the coolant will have had to travel horizontally before it before it drops out the bottom and looking up is not going to be that informative. The only thing that is going to be definitive is 'its wet'.

You can do a visual inspection around the throttle body / thermostat area to see if you can spot the leak. That is a pain in the ass area to inspect and you will likely have to remove things to get a good look. Getting eyes on things is going to be hard. Unless visual inspection points out the problem right away, cooling system pressure testers can be had for a fairly low price so I would be inclined to fast track to the pressure test. With luck the leak is small and having the system under pressure will make the leak easy to spot.

If this 1992 still has its original cooling system hoses planning for replacement of all the hoses would be a good thing, particularly if the car comes from a really hot climate. The hoses in the engine compartment can take a beating.

 

[Honcho]

Thank you very much for the info! I have read the cooling systems in these cars are a bit more complex. Good to know on the viscosity too. The spots on the trailer floor were still a clear bright green color, which I was hoping was a good sign.

Getting the car up on a lift here shortly to investigate further. I do suspect the thermostat is probably in dire need of replacement since it's been sitting with little use for so long.

Fingers crossed no head gasket issues!

@Old Guy is right- if the car has its original coolant hoses, they are probably on the verge of failing. The little ones around the throttle body become hard and crusty and weep coolant. After all, they were not designed to last 31 years.

You can remove the airbox fairly easily, which will give you a better look at the throttle body area. No need to lift the car. It should be apparent pretty quickly where the leak is.

 

[AdmiralCrunch]

After a more detailed look, I believe it's probably a hose or o-ring. Gonna have the thermostat replaced and pressure test done to nail down the leak location. Thankfully the coolant and oil are clean, and there was no indication that anything blew out the head gasket.

After this I'm probably going to take it to Ben up at Daisy Auto in MD for a full cooling system upgrade. He was highly recommended for this area in another post and seems extremely knowledgeable.

 

[Lamini]

Ben hooked me up when I went through my first tank leak. In both occasions (yes, mine has split 2x), it was because I drove with engine cover off, though that might not be the reason why it leaks). Replaced all my belts too and said I'm good for next 10yrs. Well, its been 10yrs (and +80,000 miles) and still good.

 

[Honcho]

After a more detailed look, I believe it's probably a hose or o-ring.

There are four key O-rings that seal the coolant. When I removed them from my 92, they were crushed flat and hard like plastic. They are just a few bucks from Honda and I highly recommend replacing them. I have never seen a leak from here, but given the age of the car, it's possible.