Suspect car needs new radiator: validate my diagnosis

I’m trying to help out a friend with car trouble. The vehicle in question is a 2000 Dodge Neon ES, with an automatic transmission. Mileage unknown, but I can find out if it matters.

Using a borrowed pressure tester from O’Reilly, I cranked the system up to 16 psi (the rated value of the cap) and checked for leaks.

The automatic transmission versions of this vehicle run transmission fluid through the bottom portion of the radiator - the entry and exit fittings are the two brassy-looking things at the bottom of the radiator shown here.

Around one of those fittings (the one on the left), coolant appears to be leaking out. There is no evidence of ATF in the cooling system, nor of coolant in the transmission.

I’ve never dealt with one of these ATF-through-the-radiator systems before. If it gets to this point are we looking at just replacing the radiator, or can the fitting be somehow tightened? Access to it in situ is awful, so I haven’t gotten a real good look at it yet.

Related question: The Chilton’s manual states pretty emphatically that if those two hoses from the transmission are disconnected at the radiator for any reason, then they must be replaced. (Something about internal walls being fragile.) Does this sound true?

Just FYI all cars with automatic transmissions have tranny fluid coolers in the radiators. High performance engines can also sometimes have engine oil coolers.

My advice would be to try gently tightening the fitting (make sure you use a flare nut wrench) and if that doesn’t fix it take it too a radiator shop. They may be able to soldier the leak without having to replace the radiator.

If you can’t tighten it to seal without fearing breakage, next step could be a “radiator putty” pref. drained and dry, and if that won’t\can’t work take it too a radiator shop. They would be able to solder the leak without having to replace the radiator, might have to remove and refit it though… However, if it’s not leaking dramatically either just top it up regularly, and/or leave the cap at the first click, instead of closing it to full pressure.

Thanks to both of you for the advice. I’m curious about the economics of taking it to a radiator shop: A new radiator for this car will only cost about $75 from someplace like Is it likely that a shop could patch the old one up for much less than that?

I’m thinking that if I’m going to go to the trouble of removing it, there’s no reason not to just replace the thing (vice fiddling around with trying to fix it).

Agree. If you buy the parts yourself, I can’t see how paying the radiator shop to do a partial repair would be a better bargain than just replacing everything yourself with new parts. This assumes that it isn’t too much of a pain to yank the radiator and the transmission cooler and the hoses and so on. Have you checked the shop manual to see how all those assemblies are attached?

I would not leave the radiator cap on the first click like we did in the 50’s and 60’s. The newer cars are designed to run hot and will blow out your coolant if the cap does not hold sufficient pressure. That might get expensive. Not sure if this is the case with your car but the fitting might simply be a push in with silicone o rings on it. Sometimes the silicone o rings will weep a bit when the weather changes to cold. If this is the case just adjusting the level of your coolant about once a year might handle the problem.

I had an old Camry before with the exact same problem. I put in Lucas radiator stop leak or seal or something like that from Walmart ($10). Drove the car more than 5 years after that and never had problems with the radiator. YMMV.

Tightening the fitting for the ATF WON’T stop a coolant leak. The ATF cooler is a radiator inside the radiator. Your leak is where the ATF line passes through the outer radiator.
You can try putty, but I’m not sure if it will work.

As far as the replacement of the lines goes, Chiltons supplies information to professional shops and they get that info from the car makers, I would say yes the info is accurate.
Does that mean you can’t get away with reusing? Who knows you might get lucky.

Those fittings typically screw into the radiator tank, so theoretically could be tightened. Nevertheless, I’d be surprised if tightening would stop the leak – I think it’s more likely that the tank has a crack. If so, the proper fix is to replace the radiator. It’s possible that Bars Leaks (the only brand of cooling system leak-stop I trust) might fix it (may or may not work, if it does may or may not last – but often works, often lasts, and is cheap).

No. Sounds like horsecrap to me, and is NOT mentioned in my professional repair info. I suspect Chilton’s (which is aimed at do-it-yourselfers) is trying to give some overly cautious one-size-fits-all advice to people it doesn’t believe can determine whether there might be a problem with the hose.

Definitely try some radiator sealant additive first. I’m not a fan of additives in general, but I have had these work. If it doesn’t, well, I get the feeling you’re not overly familiar with automobile mechanics, but replacing a radiator isn’t the hardest thing to do. A few important steps:
[li]You’ll need a large drain pan to catch the coolant, and clean if you want to reuse the coolant (else you’ll have to buy new)[/li][li]Drain the fluid by opening a wing-nut screw valve thing (called a petcock) at the bottom of the radiator[/li][li]Once it starts draining open the radiator cap and it will drain much faster (be ready to reposition the catch pan!)[/li][li]Once drained remove the engine coolant hoses. These only have hose clamps on them but they can be really ‘stuck’ to the radiator fittings if they’ve been on a long time.[/li][li]Unbolt the two transmission cooler lines. Again make sure you use a flare nut wrench as these fittings are usually brass and a regular open-end wrench can easily strip them (a flare nut wrench is a box end wrench with a small gap for the line to fit thru). A little tranny fluid may drip out but that’s all.[/li][li]Remove the electric cooling fan & fan shroud mounts (if they’re attached to the radiator)[/li][li]Pull the small rubber overflow hose off the radiator cap opening[/li][li]Unbolt the bolts on the top rubber radiator mounts[/li][li]The radiator should just lift out (they don’t usually have bottom bolts, just notches that they fit into)[/li][/ul]
Reinstalling is the reverse. Add a little fluid & check for obvious leaks. Then fill the radiator and start the car. The level will intermittently go down so keep adding and again checking for leaks. You’ll need the engine to get up to temperature so that the thermostat opens, the fluid level will drop a lot then so keep adding. It can also get ‘air-bound’ and again will drop suddenly when it clears.

Also: Never have your face directly over the radiator opening, it might spray hot fluid out suddenly. Be careful when your hands are near the surface of the radiator, those metal fins are sharp and will peal skin off like a cheese grater! If the car has A/C it will have another radiator-like thing in the front (the A/C condenser). It shouldn’t get in the way but be careful not to damage it. If you have to use new antifreeze make sure you get exactly the right kind! Different make & model cars use many different types now.

Good luck…

Thanks very much for all of the advice. So far we haven’t had a chance to do much beyond the initial diagnosis.

I think I’m going to recommend (remember, it’s not my car and thus ultimately not my call) that we give Bar’s Leaks a try and then, if that doesn’t work, replace the radiator.

I’ve never needed to remove a radiator before, but I have a fair bit of shade-tree experience mucking with my own vehicles’ cooling systems (changing hoses, thermostats, and water pumps). Compared to the water pump on this car, pulling the radiator looks relatively straightforward…

Anecdotal evidence here: The radioator/trans cooler in my Dad’s neon (of the same vintage, his might be an '02) just failed in this way for the second time. If this does fail while under pressure, you have now probably contaminated the trans fluid with coolant, and will need to do all sorts of flushing and replacing, etc to get the contaminated fluids out.

His solution was to separate the two, putting in an auxilliary trans cooler that is not connected in any way to the radiator. Granted, he did this as a retired mechanic with 40 years at Chrsyler, but for the thing to fail like this twice is just nonsense, and speaks to a known weakness with this part combination that just hasn’t been addresses. I’d be very wary of aftermarket “OEM spec” radiators, as they may be prone to the same issues.

Typically, the hardest part in replacing a radiator like yours is reconnecting the trans cooler lines. Leaving the radiator bolts loose until you get the lines well connected can give some wiggle room if needed.

I have a really good radiator shop in town that has done similar small patches for me for about $10 if I bring the radiator in and clean the patch area.

I don’t completely disagree with the logic of just throwing a new one in, but one issue is that cheapo radiators often have much lower quality materials than the original radiator and sometimes take some extra work to get to fit in the car. They’ll work fine, but long-term you might be better off if you can repair the OE radiator. Alternatively, if you do have a good radiator shop in town, they may be able to fully recondition the original radiator for a price that’s competitive with a cheap internet radiator and will leave you with a better part in the car.