Hello!

I have a 1986 C4 with cast iron L98 engine and I’ve started noticing some intermittent coolant leakage under the car and in the engine bay and I’m wondering if the coolant the mechanic put one year ago in the circuit is starting to corrode the whole circuit.



The story so far:

1. Car was purchased in 2021 and the yellow coolant was very rusty.
2. Yellow coolant was flushed and replaced shortly after with yellow coolant again, and by the end of the year it was rusty again.
3. I brought the car to a different mechanic early 2022, which is experienced with C3s. The circuit was so clogged that no fluid come out when he removed the knocking sensor to drain the engine coolant. He found out the rust was coming from coolant pipes springs, which were basically melting. Springs were removed, circuit was washed again and filled with blue coolant (compliance with ASTM D3306, D 1384, BS 6580.92, CUNA NC 956-16 – SAE J 1034). No more rust since then (yay!).
4. In summer 2022 I started noticing coolant leakage in the cabin, coming from the heater core. I took the joy of dismantling the car dashboard to replace the heater core. I had the chance to use it 4-5 times since then and it was behaving correctly (temps, HVAC, etc) by adding half a glass of mixed coolant+water almost every time, thought the circuit had to bleed some air due to the previous work. The only weird thing I found is the coolant expansion tank level was not moving that much from the cold position, even when the car was fully hot. Anyway the car was running fine so I didn’t investigate it further.
5. Two weeks ago I turned on the car and move it outside just for some preseason checks. When I returned it in the garage, I found some coolant sprayed in the engine bay (half a glass). I thought the cause was that I misplaced the radiator cap during some previous check, so I cleaned it and left the car there.
6. Two days after, I opened the garage again and found some coolant under the car just under the radiator on the passenger side. I was telling myself this must be the residuals from the other day, so I cleaned the coolant on the floor.
7. The situation was good for one week (didn’t move the car), then 2 days ago I found again coolant on the floor so I started thinking the radiator is leaking.

I’m in doubt if having the heater core and the radiator failing is just a coincidence (I believe they are the original), or if cleaning the circuit removed 35+ years of dirt acting as sealant, or if the blue coolant is somewhat wrong and is eating up the circuit. No coolant mixtures were done, as the circuit was always cleaned before changing from yellow to blue. Coolant in the radiator and in the expansion tank is clear.



What do you think? I'm leaving a couple of pictures of the radiator.




radiator front view

possible leaking area

 

Sounds like your system is building alot of pressure. Could be a bad radiator cap. Because if it's not filling the expansion tank then the cap is not opening under load and just building a ton of pressure in the engine. Also I just run green coolant and it works just fine. Test your radiator cap and see if it's holding to much pressure

 

Your radiator is toast (the fins are all clogged) so you need to do an exceptionally through clean or get a new one.

You will need to put the car up in the air and bring it up to operating temperature as the pressure will show you the leak. Your coolant system is pushing 40 years old so inspection and replacement are in order.

 

sadly also true. But when you get a new radiator it should come with a new cap so I wouldn't bother with testing the cap at this point unless your just curious

 

Though the radiator probably looks similar.

 

Well, I does not look like air can get through the condenser. They make combs to fix this but yours would be a giant job. I wonder how in the hell it got so smashed up. Dan

 

Does your ac work?

The way that condensor looks, you very likely have a leak and the refrigerant is leaking and then dust sticking to it creating that mud looking goop clogging your condenser fins.

Good news is that its an easy job. A pile of 10mm bolts.

you can buy a cooling system pressure test kit. that is what i did to determine that my waterpump gaskets were leaking.

 

Ouch, you're right!

I have no idea. From your comment I assume it took some years to get in this status. Could it be? But I'm unable to explain how the mechanic didn't see it

Yes, AC works. I need to remove the condenser to clean and replace the radiator i suppose. Can you please give me the model of the pressure testing kit?


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There is no such thing as a "good" mechanic that would not notice the condenser all smashed up. Dan

 

Most auto part stores like Auto Zone will lend them out for free. You just leave a deposit which is usually the cost of the tester and they will refund it when you return it. They are not that expensive if you want to own one and there are a lot of good name brand testers available.

Good luck I hope you get it figured out.

 

I’ve had cases where the car would not leak cold, but warmed up (pressurized) the leak would appear.

 

hello there
i have a quick update on the topic. after not being able to clearly understand where the leak was coming from i decided to turn on the car to test it in a different status. i was expecting coolant to spray everywhere but i'm quite astonished it didn't happen.
Considering the leak was happening under no pressure i was somewhat worried of pushing the cooling system to its nominal pressure, so i decided to stay under the thermostat opening temperature for this test.

At 70°C i switched off the car. I found no leak from the radiator or under the car. Then i've opened the radiator cap and i was surprised some coolant spilled out as i was expecting no pressure due to the fact the circuit is closed to the engine block as the thermostat was closed. anyway this is even more strange as with some pressure applied the radiator wasn't leaking, while 1 hour before it was, and the vehicle was cold!
What do you think?

 

Here's what I think, whether the radiator is leaking or not, based on the picture of the AC condenser (which doesn't looked smashed to me, it just has that much build-up on/in it)...the radiator needs to come out to be thoroughly cleaned and since it will be out...pressure tested! I would remove the radiator and take it to a real 'radiator repair' business, in the meantime I would clean the AC condenser! Go to a home improvement store and go to the area where they have window AC units and ask for AC coil cleaner (you can get gallon jugs that you add water to or spray cans) a couple spray cans will do. Spray the foaming coil cleaner into the fins of the condenser from the engine side (spray towards the front of the car) this stuff is pretty cool, what happens is, the cleaner comes out mostly liquid but turns to kind of an expanding foam and will "push" dirt/debris out of the fins at the same time clean/shine up the metal. Apply the foam, let it set for 10-15 minutes, spray it out with water. I'd do it a few times over. Make sure to thoroughly rinse the whole area with water when finished. Now what's the verdict with the radiator, either you reinstall or are buying a new one to install. And for what it's worth, since you'll have the coolant drained again, if what drained out is still rusty and your new blue antifreeze isn't looking so great, I'd be flushing the engine side of the system one more time and starting with fresh antifreeze! Just my $0.02, good luck👍

 

i have a couple of questions more if you can help me, i read the FSM carefully but i dindnt find any information about the following:

1. when disconnecting the trasmission oil lines on the radiator, does the transmission oil comes out?
2. do i have to disconnect the AC condenser?
3. if i disconnect the AC condenser lines to remove it, does the R-12 AC refrigerant/gas comes out?

Thank you!

 

You need a new radiator.

 

[QUOTE=m4rk_;1606810116]i have a couple of questions more if you can help me, i read the FSM carefully but i dindnt find any information about the following:

1. when disconnecting the trasmission oil lines on the radiator, does the transmission oil comes out?

a little bit will dribble. u can cut the fingers off a rubber glove and use tape to mostly prevent leakage.

1. do i have to disconnect the AC condenser?

only if you are replacing the ac condenser. did you clean it? did you determine what that goop is that was on the passenger side of the condenser?

1. if i disconnect the AC condenser lines to remove it, does the R-12 AC refrigerant/gas comes out?

does your ac work? chances are it doesn’t work. in which case its most likely already leaked out. depending on where you live, you can buy refill kits that in my experience work phenomenally IF you also buy the vacuum manifold pump set to suck down your ac system prior to refilling.

This takes a small investment to buy the ac stuff, alternatively, you can take the car to a shop and get them to find out where the leak is (that condenser?!?) and refill the sustem.

Thank you! 👍👍

 

[QUOTE=VikingTrad3r;1606810359]Thanks VikingTrad3r for all the information!!
The AC is working, might require a small recharge but its going ok so far.
I managed to clean out the stuff on the condenser using a brush, it was similar to dust or pollen. Probably the greasy leakage acted as a glue for all stuff collected down the road when travelling, and that was the result. I'll keep it inspected.

In the end I'm going to buy a new radiator, because it's not crazily expensive and I also need to change the seal behind the crankshaft pulley (located behind the timing case) so i need to remove the radiator anyway. Better take the opportunity to do a clean job.