I think my plan is to remove the radiator and pump and flush the block using an adapter and garden hose at the back drain. Then flush the radiator upside down to remove most of the large stuff currently in there. Then once everything is back together run some radiator flush in there a few times till it runs clear. Hopefully this will work fingers crossed. I will post updates once I am able to get around to all this. Waiting on the adapter to come in work will be getting in the way this week.

I'm hoping to head to Chrysler at Carlisle Friday so maybe I'll keep my eye out for a spare water pump. Hoping to find a 2 barrel intake too.

Update on the cooling issue. Roadster with 225 Slant Six

I flushed the blocked with a garden hose and adapter hooked up to the drain plug in the back passenger side of the block. Flushed it from both radiator hoses. Filled it with vinegar, let it sit, flushed then rinsed with baking soda water then plain water. Did that process twice. All the flushes were run until clear. Back flushed the radiator several times and used 12 psi of compressed air to help push the water through. Got some crud out of there but did not use vinegar since its an aluminum radiator. New Stant 180 thermostat, new water pump, and added a piece of screen before the radiator to catch anything else from getting into the radiator. I replaced the bottom radiator hose and added a new spring as well. I also built a shroud that seals to the radiator so the electric fan should be working a lot better. After all this the temp gauge still got up to about 230 with a short drive and just at idle. Replaced plugs with the recommended NGKs with the rings removed, reset the points gap, set timing to 5 BTDC to rule out the engine running lean and making it run hotter. When it was idling in the driveway I used an infrared thermometer to check the block and head for hot spots along the passenger side and everything was relatively even. When I checked the radiator it seems the sides were about 80 degrees and the middle was about 170-180. The radiator was in the vehicle when I purchased it and is a 14"x 14" 2 row aluminum with the inlet centered at the top and the outlet bottom passenger side. https://www.mishimoto.com/honda-civic-r ... 92-00.html

Is this just how the radiator flows since the hot water is coming into the middle or is it most likely clogged? Or is this radiator just too small to handle the cooling needs of a 225 slant six?

The same company makes a radiator the same dimensions 14"x14" but is a 3 row and the core is .35" thicker Would this be better than the 2 row?

I wouldn't run screen in front a radiator in general.

I'm assuming you're joking about running a Civic radiator ...14x14"? That's about 66% of even a non-AC stock radiator. Note that even the maker of that radiator calls it a half-sized radiator. A Civic has greatly reduced losses and therefore needs far less cooling than a Slant Six.

I'm not convinced your issue is the radiator regardless, but it sure isn't helping you. Same for the electric fan.

Its just what was in the car when i purchased it. Back when i started this thread i mentioned the size of the radiator hoping someone would chime in whether that was the issue but nobody did. What would be a good "size to run" for this car? Should i just look up a factory radiator and determine the square inches/ cubic inches of the core size and use that as a baseline. Would a 1 row with larger coolant openings be better than a multiple row radiator?

Are you saying the electric fan isn't the issue or the electric fan isn't helping?

Some general comments:

*You don't say if the infrared gun temps are also at 230F or just the temp gauge? If the gun numbers are significantly lower, I'd distrust the temp gauge.

*A stock 225 radiator has a core that is about 17" x 17". You don't say if the radiator you have is 14"x14" on the core or the whole thing. Either way it's a lot smaller than stock, regardless of what it's installed in.

*Radiators are most effective when they have the most frontal area. In other words, a single row radiator with a lot of square inches is better than a smaller radiator with 3 rows. That's because the third row is seeing hot air from Rows 1 and 2. And, the thickness of the core hinders airflow. I'd guess a third row is not another 50% but more like 15 or 20% cooling capacity.

*The vast difference in temps your gun in reading on the radiator is 'not right'. You shouldn't see a 100F difference. That suggests some of the tubes are clogged or ???

*I'm saying electric fans, unless sized by the OEM, are often a hindrance. People underestimate the amount of airflow needed, and they also fail to recognize electric fans draw a lot of amps and those amps gotta come from someplace.

The gun temps along the block and head were around 190-200 but the front of the head where the themorstat housing attaches and the temp gauge sensor goes in was reading 230, same as the temp gauge.

The 14x14 is the core size. I realize its smaller than the stock size but can't go throwing money at a new radiator to find out there is issues in the block too. I'm trying to find a larger radiator to borrow from a friend to test it out on the car.

That makes sense about the 3rd row being less effective due to having 2 rows in front of it.

I jacked the front of the car up to help purge out air while filling with coolant and after doing this the car stayed at 180/190ish on the temp gauge at idle and the temps were a lot more even across the front of the radiator. I'm assuming there just wasn't enough coolant to pump through the whole radiator before.

There is no room to run a mechanical fan since the water pump is not centered in the block. But with the shroud the electric fan seems to be pulling a lot of air through the radiator. You can feel the vacuum on the front of the radiator across the whole thing with your hand an inch or two away from the core.

The screen I was talking about is not across the front of the radiator its just on the radiator inlet hose as a simple in line coolant filter to prevent junk in the engine block from getting into the radiator core.

I know this site isn't about hot rods and I understand that makes it inherently more difficult to diagnose and over come problems since space is limited. If testing a larger radiator makes a huge difference then I will try to have a radiator made that is 14"x21"core size (294 sq in) to equal a stock 17x17 (289 sq in) radiator. If I can spare the room I could make it a little taller to add more cooling relief.

I bought a jeep with the 4l I6 that had bad cooling problems. With radiator out (for replacement, but also for access) I removed the thermostat and hooked an adapter to one radiator hose that allowed me to connect a garden hose and an air line with valve. I would allow the block to fill with water then hit it with short bursts of air. You should have seen the crud blowing out the other radiator hose! Repeated till it was fairly clean then swapped hoses, lather rinse repeat. (Also went both ways through heater hoses) When I couldn't get anything more out I hooked up a "radiator bypass" I made from pvc pipe. (90 each end, t in middle open stub sticking up) filled the engine with water and added some phosphoric acid, started the engine and let it run till it got good and warm. Then I shut it off till it cooled down and restarted it, ran till starting to boil (the pvc joints started to fail) let it cool till I didnt burn myself as I flushed with the adapter again. Got an unbelievable amount of rust and crud again! When it finally ran clean both ways I replaced the water pump and thermostat. The block behind the water pump had no trace of rust! Put in all new hoses and radiator (old one had blown a tank off) No further cooling problems.

This is probably extreme unless your system is very bad, but it WILL get things clean.

_________________
Dave

1977 d-200 crew cab ex-army pickup wants it's /6 back
1962 Valiant 2 door, 170, three on the tree
1972 d-100 parts truck
80 volare wagon now a parts car