Getting my 1972 Premier President's radiator overhauled

Post cooling system overhaul, I have found a notable change in the rate of decrease of coolant in the radiator.

BHPian vishy76 recently shared this with other enthusiasts:

Radiator overhaul & coolant elbow change

The radiator has been an achilles heel ever since I bought the President. It seems to be the original unit which came with the car when it rolled off the factory floor, but it had a couple of design flaws which had reared their ugly head as it aged:

The coolant reservoir cap on my radiator bolted onto a neck. This neck would always spring up a leak from the bottom where it connected to the top tank. Another issue with the neck was that the collar where the cap sat had deformed considerably
The bottom of the radiator has a drain plug. This is known to work itself loose sometimes and cause leaks, leaving one stranded unnecessarily

Apart from these issues, the core itself had a couple of minor leaks. Despite this, I have never faced a single instance of overheating during the course of my 3000+ km ownership period. Engine temps have always been in the 75-90 degree range (this cooling system doesn’t have a thermostat). The car would lose a lot of water though. I had to top the radiator off by about 200-300ml every 20-30 km.

I decided to remove the radiator and have it serviced. 4 nuts secure it to the side panels, 2 bolts secure it directly to the body at the very top and one bolt secures it to the subframe (many mechanics skip this one. I did too).

The best way is to simply remove the side panels (held in by 1 10mm nut each), undo the 4 nuts which hold the radiator studs onto those side panels and then undo the two bolts holding it directly to the body. The upper and lower radiator hoses can be a breeze or a pain in the proverbial place to remove depending on the orientation of the clamps that hold the hoses.

Once the hoses are off, the radiator can be removed easily if the engine is equipped with a full flow oil filter at the bottom. If it has a bypass filter at the top like mine did, it will need to be tilted slightly while removing.

With the radiator out, the extent of leaks could be judged easily. The core had a couple of leaks as is visible in the image. Also note the top neck and the bottom drain plug, both of which create issues as the radiator ages:

My mechanic suggested I entrust the overhaul job to a very small roadside shop named “Baroda radiators”. I don’t like availing any machining, lathe or welding services without my mechanic’s referral so I went with his suggestion.

The gentleman who owns the shop suggested the following:

• The neck could be repaired (again), and a new cap fitted
• The entire core would be cleaned with acid and a couple of suspected leaks sealed
• The bottom tank where the lower radiator hose would locate had a weak spot. It had almost begun to leak
• The top tank also had a very minor leak

I was very apprehensive of retaining the neck. My simple suggestion to the owner was that he eliminate the neck completely and locate the cap provision on the top tank face. After showing him that the neck was also not accepting a cap perfectly, he agreed.

I also suggested he knock off the drain plug at the bottom and solder a brass piece to it. After realising that I had done my homework on the subject (at least in theory), he asked me to pick the radiator up the next day with a new radiator cap. The original TEKIL branded cap was a dud. The cap gasket was ripped and spring action was poor.

The radiator was ready the next afternoon. I was charged Rs. 1,200 for the entire job. Not bad considering I get to retain my original unit and the fact that a new one costs close to 5k now.

I hadn't really expected that it would be painted too. Although I am not a fan of the black paint. It traps heat unnecessarily and also gives off a weird smell once the radiator heats up:

I gingerly went about trying to install it. Before elaborating on what occurred next, I would like to shed some light on the Fiat’s cooling system. The flow diagram for it looks as follows:

Engine block → Water pump → Radiator top hose → Radiator → Radiator bottom hose → Coolant elbow piece → Engine block

The coolant elbow piece is shaped like a rhombus with rounded edges at one end that plugs into the engine block, and a hollow cylinder at the other to accept the lower radiator hose.

When I had removed the hose, I noticed extensive corrosion on the elbow. However, I had dismissed it off as normal wear and tear considering this system doesn’t even use coolant.

It is only when I tried to slip the hose onto the elbow that I realised how brittle and weak it had become. Chunks of the elbow came off. Even with the hose tightened on top, it started leaking. I had no choice but to change it. The grille, radiator, fan, water pump pulley and fan belt had to come off so that I could access the two 13mm bolts securing it to the block.

Old elbow. Even new ones are made of some low quality alloy. I don't expect them to last more than 2-3 years at best:

The point on the block where the elbow bolts on:

I ordered a new one which arrived in about 4 days. The new elbow had an outlet for a bypass hose to the water pump which my car didn’t come equipped with. I had the outlet threaded and inserted with a bolt (used thread locker too) to delete it.

I reused the old bolts by putting grease on the threads, used a gasket I made myself out of thin cardboard and also applied anabond before securing the new elbow to the block.

Everything including the side panels back in place:

Finally, I assembled all the removed parts, put the hoses back, topped up the cooling system and started the car. Ran it till the engine got up to temp, and was glad to find zero leaks.

Post cooling system overhaul, I have found a notable change in the rate of decrease of coolant in the radiator. This is an open cooling system so it loses coolant by design, but I am glad to report I have driven the car around 70-80 km post this exercise and have not found the need to top off water at all.

I will pass final verdict on how much it has impacted thermal efficiency for later since ambient temps are anyways very low here. The only thing that remains to be done is flush the system using a garden hose at the radiator cap end and draining via the 15mm drain plug on the engine block next to the distributor. That should ensure a lot of the mucky water inside the block jackets is flushed off.

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