MGB - coolant pump replacement (Part 2)

Today's post continues the efforts around replacing all of the smaller pieces of the cooling system. It started with just swapping out the coolant pump, but the hoses were old, the hose clamps rusted on, some parts desperately needing paint, etc. So, today's post covers the second phase. In the last post, we identified parts and tore everything down. Today we clean it up and start putting it back together. But first: Hapy Halloween.

Clean Up
There were a few original pieces that needed to be cleaned up and painted before they were re-installed. I reused the pulley cap, the accessory pulley, the pipe that connects the heater to the system and the overflow bottle mounting strap. Using 80-grit sandpaper, I took down the rust and then followed with steel wool to prep for paint. I then shot them with high-gloss black Rustoleum. When I sanded on the overflow bottle, I discovered it was brass, so I spent a bunch of extra time cleaning and polishing it instead. It will probably be the shiniest thing under the hood.

bottle while cleaning

bottle as removed

While the parts dried and cured, I decided I would de-scale / de-rust the inside of the radiator. I knew this was my opportunity to get after it, especially if I didn't want to open the cooling system again. The radiator is held on with 4 bolts, accepting a 1/2" socket. Once removed, the radiator lifts straight up. If you don't lift straight up, some otherwise not drained coolant will come out. I drained the rest into a disposal bottle and then ran water through it using a garden hose. I kept sending water through until the water coming out was clear. the discharge went mostly into a disposal bottle with some spilling on my driveway. Between the rain and a post-cleaning hose-off, I think the local animals are safe. I then poured 2 quarts of vinegar into the radiator and topped it off with distilled water.

harness pull-back

Something very similar to the radiator treatment I did to the heater unit. I attached old hoses to either end and flushed with tap water until it ran clear. Then, I added vinegar to the heater by filling from the lower bib until it started to bubble out the top. Through raising and lowering the hoses, I was able to get the heater core completely filled with vinegar.

I left the radiator and the heater with their de-rusting solutions in place for a week. Then, I drained them into a disposal bottle. Vinegar is an acid that will leave the remaining metal prone to rusting if left alone. To neutralize, mix one cup of baking soda with a gallon of water. I poured this mixture into the radiator and heater units and left them alone overnight. The internet says it only needs 10 minutes, but I was out of time that day anyway. Once the neutralizer is drained, flush again with water. Once they were both running clear, scent-free water, I taped off the radiator fins and shot the rest with very high temperature (VHT) flat-black paint. The same paint I used on the brake calipers. While the radiator shouldn't get anywhere near the heat that brakes or exhaust get, I figured better use that than Rustoleum which may not be able to handle 200*.

heater flush

While everything was broken down, I had an unexpected garage visit from my now-19 year old son T. He wanted to jump in and help. So, we pulled the main harness off the passenger inner wheel arch and taped it off for paint. After he left, I pulled back the engine seal, and masked off the outer wheel arch (fender / wing). I tossed a moving blanket over the engine, cleaned the inner wheel arch and shot it with the same orange I used on the driver inner wheel arch. Similar to that paint job, orange paint dust settled on lots of parts, but I'll hit that with the shop vac after the rest of the bits are assembled.

Re-Assembly
I started with setting the gasket on the coolant pump and threading the bolts through. The bolts will help hold the gasket still. The internet doesn't agree on whether a layer of goop on the gasket is necessary or not. I did not put any on, believing that if it leaks, I can always tear things apart and add it. It leaked after all, so I tore it down and re-did this part using Permatex blue gasket maker. This stuff is designed for something like this. Simply peanut-butter both sides of the gasket with a thin (about as thick as a sheet of notebook paper) layer of the Permatex. Carefully set the gasket onto the pump and then the pump onto the head taking care not to get goop into the head. I did this by pushing the bolts through and using them to line things up. The 4 bolts which hold the coolant pump to the engine are different lengths. Since they are threading into the engine, make sure you use the right bolts in the right spots. Too long, and too much torque could create a crack.

rad flush

Once in place, the manufacturer and the interweb says that the coolant pump gasket needs to be heat-set. One way is to assemble everything and then run the engine (without coolant!) for 30 seconds or so to generate the heat necessary to make the seal happen. I found that alarming, and chose to go with option 2: using a drill. This was really kinda weird. Either way you need to put the pulley on the pump. With option 2, you put the accessory belt around the underside of the pulley, and the other end around the chuck on my drill which I held near the thermostat housing. I created tension by pulling upwards on my drill and then fired the trigger. Once I got it running consistently, without running off either end of the chuck, I let it spin for 2-3 minutes... or the length of one old Black Sabbath song on the radio. War Pigs, I think. When I did all that, it leaked. So, I re-did it with the Permatex like I described above, and didn't heat-set the gasket, and it's holding fine. Use the goop.

With the pump ready, I re-installed the radiator. 4 1/2" bolt/nut combinations later, the radiator was in. This was super-easy and with the new paint it looks much better too. Then, I put in the thermostat housing.. without the thermostat. There's a reason for this: the thermostat sits closed so coolant can't pass, but the coolant filler is above the thermostat, so you need to wait while coolant trickles in. Who has that kind of time? Instead, once the hoses are on, you fill without the thermostat in until you're full just below the lip of the head. Then, drop the thermostat in.

Next, hook-up the hoses, starting with the lowest radiator hose to the coolant pump followed by the upper radiator hose to the thermostat housing. In each case, I considered where the screwdriver would need to be in order to loosen/tighten the hose clamp before putting on the hose. Taking a few seconds to consider that, and even popping the clamp on there loosely, but in the right position, saved me a headache later.

Connect the lower radiator hose to the narrow pipe that leads back to the heater, and then the heater hoses. If you have or used to have a coolant-based choke, you have the small hoses that lead from the rear of the head to the narrow pipe, though the carb. My carb had been swapped out, so there was a hose connecting these two. I will form a more formal blank for both ends, but knitted things together for now. And then there's the hose from the radiator to the overflow bottle. And installing that overflow bottle. That's easy. The bottle is held by a steel strap which is held in place with 2 1/2" nuts addressed through the passenger front wheel well.

Fill as much as you can with the thermostat out, and then remove the thermostat housing, and install the thermostat. The new cork gasket held very well, not requiring any Permatex. Add more coolant, burping the system by squeezing the lower radiator hose until you can't reasonably get coolant into the filler hole. But then what do you do? The MGB cooling system is simple, but the routing of the hoses and location of various components creates many opportunities for air bubbles. For example, the heater core is at the system high-point, but there is no facility to bleed air. I used the little hose bib sticking out of the back of the head to fill once the coolant filler at the front of the engine was full. I continued to burp the system until I heard coolant start to appear in the overflow bottle. The interweb advice is to have the bottle at 1/2 full, so I continued filling from the back of the head, holding the hose above the heater until the overflow bottle was 1/2 full.

Sigh..
That's it for today. All that remains is a test start and then a test drive. At some point, the seemingly endless rain will pause long enough for me to take this roadster out to verify the clutch hydraulics...  brake hydraulics... coolant re-do... steering... front suspension.... fuel system revitalization and, of course, the floors. It has been a year since the little British car drove around, so I'll be dedicating a post to that... once it happens.

Thanks, as always, for following along.