Interested in the collective forum experience and wisdom. 1988.5 USA 328 (completely unmodified). After pulling the car out of winter hibernation, I noticed a small drip of coolant under the passenger front while idling in the driveway. Engine temperature never became hot, never driven, etc. All hose connections/hoses/bleed screw/radiator temp sender gasket/heater core were dry, so I anticipated this would be a straightforward radiator core leak. Removed the radiator and brought to my (only) local radiator shop. After extended pressure testing, no leak was found (although they were understandably unable to test "hot"). I was given a small packet of brown powder stop-leak substance which I was instructed to pour into cooling system and assured this would not cause any issues or concerns (there is no label, it's about the size of a condiment package, and it's "not what I can buy at the parts store"). And yes since the radiator is embossed on top they were aware it's from a Ferrari. After reinstallation and refilling the system this morning, I find a trail of fluid along the bottom front of the passenger side radiator core panel which begins at about 180F indicated (presuming this is thermostat opening temperature). At this point I envision my options to be: 1. Pour a vial of UV coolant dye into the system to attempt to localize leak source, then (if successful) remove radiator and repeat pressure testing focusing on this area. 2. Pour the brown stop-leak powder in - which I am reticent to do - but this shop fixes radiators every day for the area (no other shops within 75 miles) and is quite competent in their role. 3. Re-core entire radiator. I'm not sure who in the area would actually be able to do this, and as I would need to preserve a completely stock appearance not sure if feasible. 4. Replace radiator. I am aware there are aluminum replacements, but I would need to (somewhere) source an original radiator (currently out-of-stock with last list price of $3.5K - which is why this is last on the list). Are there any other options I've not considered? Any advice for me? Thanks for your time!
Start with 1. Find the leak before you "fix" it. Add thew UV stuff, run the car enough to circulate it, but not get it hot. Then pressurize the system to 15 PSI and for the leak. Don't do 2 ever. Well, maybe on a 20 yrs old Honda.
Tighten up the hose clamp on the bottom rad pipe, it can weep a bit, especially after having been removed. Is your radiator bleed screw leaking? Might be dribbling and makes it look like it is dripping at the bottom. The bleed screw gasket may have perished, at the least snug it down. Do not use the stop leak, if it the silicate type it can form a coating that can't be removed and can block a heater core. Other types tend to be temporary fixes, and introduce chemicals and metals that will not be good for the long term. Only use on an old beater car where you want to get another year or two out of it. The Nick's Forza aluminum one looks like a good product, and is supposed to be a direct bolt in. There is one good used on on ebay for a fair price right now. The store is Prevet_03 The UV dye approach sounds good. Using some JB Weld on the tank join if you find the weep will hold if it is a very small leak.
I agree that you shouldn't use the stop leak. Find the leak. If its the radiator you can just have a custom aluminum radiator made. I do this for every custom hotrod I build. you can either measure your current rad or send it to them for an exact match with brackets. Tons of companies do this, becool, griffin. Last one I had made was around 800$
If you can't locate the leak, here's some information that might be helpful to you. I have a 1967 vintage 330 and recored the original radiator. After several years it developed a pinhole leak at one of the soldered joints due to repeated thermal expansion and contraction. I had good luck stopping the leak with Prestone Stop Leak. This product contains a fine bentonite clay which is relatively inert to the metal in the the cooling system. After a few years, you can drain the cooling system and remove the residual clay and refill with fresh coolant. The bentonite that stopped the leak will remain in the system.
Thanks to all - and an update: Yesterday I put some UV coolant dye into the system, and on running to temperature in the driveway - the radiator no longer leaked. Obligingly the passenger heater core did, but fortunately I had a spare so I replaced it. However now on multiple episodes of running to temperature (i.e coolant fans turn on) there is no longer any identifiable leak whatsoever (and previously the radiator leak was at the bottom of the core tubes, not the heater leaking down). Cooling off overnight and running again today produced similar results. The UV dye package does not list any stop-leak additive, and the previous brown substance remains safely on my workbench. Oldest Honda only 16 years so not yet a candidate at this point Spontaneous leak resolution seems sortof unlikely, probably at this point need to drive it for a bit - I do expect will recur in time and thinking probably represents a minute leak in radiator. Anyone have a spare (intact) original 328 radiator they wish to sell? I saw the ones listed on eBay, but both look a bit damaged, and really for originality need to stay factory. Also - if anyone needs - I purchased a pack of about 30 of the 6mm ID/10mmOD copper washers for the bleed screw, so have some spares - send me a note if you'd like me to mail you one. Thanks to all!
