Overheating and questions thermal sensors

[maillemaker]

So my 1990 Winnebago Warrior started overheating on a 1300 mile trip a couple of weeks ago.

Thought it might have been the thermostat, since at one point the temp spiked and then dropped within seconds, but when I started draining the coolant and looked down in the fill neck I could see all kinds of mineral deposits around and in the radiator cores.

So I drained the system and put in 2 bottles of Prestone Flush and used the RV as my daily driver, letting the solution work for a week.

Today I drained the system again. The fluid that came out was pretty clean. I looked down the filler neck and the deposits are still there:



I took the RV for a test drive down the interstate and sure enough when running for 30 minutes between 65 and 70 it was running hot.

Before doing this I put in 2 bottles of Blue Devil radiator flush and filled the system up with distilled water. I'm going to drive it for another week but I suspect I'm going to have to replace the radiator.

I want to put in a dual temperature gauge to monitor both coolant temperature and transmission fluid temperature.

This is the kind of gauge I want - wish I could find one that was cheaper:

https://www.amazon.com/dp/B00Z25HM68/?coliid=I3MLPVUV4CCRPX

The question is, where to put the sensors?

My rig is a 1990 Winnebago Warrior, built on a Ford E350 chassis with a 460 engine. I don't know what kind of transmission it has, though it does have automatic overdrive.

I have heard of a test port on the side of the transmission that can be used as a plumbing port for a temperature sensor. Is this it?




One thing I noticed is the bottom radiator hose, rather than going straight to the water pump, first passes through this aluminum block thing. I think this might be an oil cooler?




So if I understand the flow right, the water comes out of the radiator and goes back to the inlet on the outside of the water pump, and then enters the engine through an opening in the block behind the pump. Then it comes out through the thermostat opening and goes back into the radiator. is that right?

I see there are also some bypass hoses going from the water pump up to the thermostat area, and then out and up to the heater core (and also tees off to go back into the house to heat up the motor aid water heater and the internal cabin heater). There is also a bypass return line going back to the pump. Is that right?

I'm thinking of using this fitting in-line with the top radiator hose to insert a thermal sensor for the coolant:

https://www.amazon.com/Water-Temp-Joint-Pipe-Temperature/dp/B01FTLUQ4O

Though I'm not sure which size to get for my radiator hose. I think this is my hose:

https://www.autozone.com/cooling-heating-and-climate-control/hose-upper/dayco-hose-upper-/66528_0

This hose varies in ID form 1.5" [38mm] to 1.81" [46mm]

So I guess a 40mm fitting should do.

Of course being in the middle of a rubber hose run I will have to run a ground wire to the fitting (no doubt what the screw is for).

What do you think about my choices for hooking up thermal sensors? Any suggestions?

Steve

[maillemaker]

I don't know how you even find that information. It's not generally provided from what I've seen:

https://shop.advanceautoparts.com/p/carquest-radiator-432195/15920038-P?searchTerm=radiator

I've submitted a question to ask.

Not sure how I'd get the information for the stock radiator, either. I guess I could pull out my calipers and eyeball it.

Steve

[MEXICOWANDERER]

The A/C condenser blocks access unfortunately.

But the tube count per inch and fin count per inch as measured above is critical. CHEAPO radiator replacements can replace a three row radiator with a four row radiator yet be WORSE new versus new right out of the box.

The school of hard knocks.

[maillemaker]

Great ideas, Gjac - I have a IR gun from HF.

Steve

[Gjac]

You can check your radiator for proper cooling with a cheap IR gun from HF. Take a series of reading from top to bottom in a 3 in grid pattern once the engine is up to temperature. Clogs in the radiator will show up as cold spots and usually show up in the center of radiator in front of the fan clutch. You should read about 200 degrees at the inlet on top and 30-50 degrees cooler at the out let on the bottom if your radiator is cooling properly. you can also back flush with a garden hose at the outlet with the thermostat removed and use a pan under the lower hose and see how much sediment comes out. Also the temp sensor in the left head can go bad and give a false reading, shoot the sensor and the T-stat housing with the IR gun and compare those readings with your gauge readings. Let us know how you make out.

[MEXICOWANDERER]

The classic is OXALIC ACID. You can find the ratio of weight to liquid on line.

But low Ph acid by itself is pitiful. It needs to be titrated and neutralized by a high Ph agent and it's the neutralization that does all the work. Use 50 flushes of acid vinegar in a coffeepot and it does close to zero.

Do one vinegar flush but neutralize it with baking soda and presto lime and scale are gone.

Now did you think baking soda alone on a battery cleaned everything so shiny 😉 ?

[maillemaker]

Call me silly, but you *DID* check that you don’t just have a bad thermostat or seized clutch fine ...... right?

Either one of those will cause exactly the symptoms you describe and not respond to any magic flush potion.

I actually bought a thermostat, as I thought that was the problem. It was when I was draining the coolant to do that that I noticed the sediment in the radiator. So I did not replace the thermostat.

I'm a bit concerned because the Chilton manual says the thermostat should have some kind of sleeve gasket which I don't even see how that would fit on a thermostat since it looks like a flying saucer not a cylinder.

Maybe I'll order a Motorcraft thermostat instead of the one I got from O'Reilly.

I did not check the fan clutch.

Steve

[RLS7201]

If you elect to replace the radiator, make sure the new radiator has the same "fins per inch" as the old radiator. A lot of the aftermarket replacement radiators are of reduced quality. The fins are what transfers the heat to the air. Less fins = less cooling.

[JaxDad]

Call me silly, but you *DID* check that you don’t just have a bad thermostat or seized clutch fine ...... right?

Either one of those will cause exactly the symptoms you describe and not respond to any magic flush potion.

[maillemaker]

Can anyone identify this coolant line?

There is a tee off of the bypass line. It is a metal run with rubber (permanently attached) end hoses. They appear to be 3/8 or 1/4" lines, not sure. It runs from the T into the bottom of the radiator. It's not a transmission coolant line.

Here is the T fitting off of the bypass line going to the heater core:



Here is where it terminates at the radiator:




Full size photos here:
https://imgur.com/a/CUVIFC0

Steve

[maillemaker]

Remove the radiator and have it professionally cleaned.

Probably not an option. I can get a new radiator from Advance Auto for $192 with 25% discount (if you put it in your shopping cart but don't buy it, 24 hours later you get a 25% discount offer). I suspect cleaning the radiator will cost at least as much.

But more importantly, I live in an HOA so the RV cannot sit in the driveway for more than 24 hours.

It's possible I could remove the radiator while at the storage unit, but then I don't have all my tools at hand and I'm sure I'll get half way through and need a tool back from the house.

If I go new radiator it will probably be easiest, fastest, and cheapest to just replace with a new one.

Steve

[eHoefler]

Remove the radiator and have it professionaly cleaned. They will remove the tanks, soak the core, rod all the tubes and re-assemble. When done, it will be like a new radiator.

[maillemaker]

Since that oil cooler looks like it is aluminum, I'm thinking any kind of lye-based cleaner is a no-go as it will attack the aluminum. Likewise I have motor-aid and a heat exchanger in the house for house heat from the engine - I don't know if any of those components are aluminum or not.

I'm going to let this Red Devil flush do its thing for a week but I'm betting it's not going to work.

Steve

[garyemunson]

You are correct as to coolant flow direction. I think you will find that replacing the radiator will make the problem go away for another 25 years and with a good radiator, the factory gauge is all you need. The inside of the radiator tubes just get corroded over the decades and no chemical will really do a very good job (well, maybe Red Devil lye but that might just eat clear through a spot that's already been corroded thin). In the 'good old days', radiator shops would unsolder the top and bottom tank and use pieces of brazing rod to 'rod out' each tube. The price of radiators has not gone up as fast as the cost of labor to fix old ones so a swap is the best choice. I'm sure that aluminum thing is an oil cooler as you suspect. A new radiator is what you need.