Am I overheating?

[MSM]

The header tank shouldn't be an empty container and I believe that is your issue.

Good luck, Chris

The header tank for the 3.8 has 2 connections and that for the 4.2 has 3 connections. If your header tank is empty as you say, the coolant flow through the radiator will be short circuited and not give much cooling. You either need the correct header tank with the correct internal plumbing or you could temporarily disconnect and blank off both connections of the third, smaller hose, that goes from driver side of radiator to header tank. That then turns it into the simpler, 3.8 type header tank system, and hopefully when you run the engine all the coolant then goes through the radiator to be cooled by the fan.

[paulsco]

I just thought I would update you on my progress or lack of, so far.

There were a couple of things that I thought might be adding to the problem:

To fit AC I had to modify the pulley system.

I replaced the double V pulleys with single V and at the time, couldn’t get hold any Series Two water pump pulleys, so used what I could get.

I was running the water pump on the same belt as the compressor and decided that there was too little wrap around on the water pump pulley to be sure it wasn’t slipping.

The header tank wasn’t the correct design as it didn’t have the pipe through the middle so this needed replacing.

I pushed the boat out and bought a Series Two water pump pulley and an alternator pulley to run the compressor; my alternator is running off the crank damper.

The Series Two water pump pulley is about 4 inches in diameter and the one I had been using was about 5 ½ inches, so I thought the pump would flow more water with the new pulley.

With a Series Two belt and tensioner, the set up is the same as the Series Two.

I decided if I was going to replace the header tank I might as well go for something that looks good and bought the Cambridge Motor Sport curved tank.

This is a beautiful piece of kit, but I was rather disappointed that it used metric bolts. Why??

5/16 UNF bolts are readily available!

Also the measurement between tank brackets was 11 1/8”, my original mounting bracket is 11 ¼”, so I had to make up some shims to make it fit. I also had to grind a bit off the top of the mounting bracket to provide clearance under the tank.
The hoses needed shortening as well.

It comes fitted with a 13lbs pressure cap??

It is such a shame that something as expensive and well made as this is spoiled because it is not a direct fit.

I bought a standard otter switch and replaced this with the tank and swapped out the thermostat again for the ‘original’ with the sleeve.

I filled up the system again and started the engine.
The temperature started climbing again and when it reached about 95 C on the gauge the fan kicked in. It ran for some time but failed to go off.

The temperature remained high, but the engine didn’t overheat. The fan was pulling down the temperature on the radiator core to a ‘warm’ level, but all three tank hoses were hot as well as the radiator side tanks, header tank and the bypass hose?

So… the fan is pulling down the temperature of the radiator core, but the header tank is not getting cool enough to turn off the otter switch?

The only thing I can think of is that there must be some sort of flow problem.
The pump is rebuilt; the block is clean; the thermostat does not appear to be cutting off the bypass flow, but otherwise appears to be working; the radiator is an uprated re-cored unit and does get hot before the fan cools it, so I cannot see that this could be blocked.

The temperature gauge may possibly be reading high, but this is not the problem in itself.

I am not sure why the header tank and radiator side tanks would remain hot if the core is cool unless somehow the core was being bypassed.

I am at a loss as to what to try next









Thanks,

Paul

[MSM]

I am not sure why the header tank and radiator side tanks would remain hot if the core is cool unless somehow the core was being bypassed.

Presumably you are feeling the temperature of the radiator core by placing your hand on it and trying to judge the temperature with your palm. If the fan is running, which I presume it is, the cooling air will be howling over your hand giving the impression it is cool compared to the radiator tanks which will feel hot. You really need to try and accurately measure the temperature difference between the inlet and outlet tanks, you are looking for about 10 deg C if all is well.

I had a problem on another car where the radiator fan came on and stayed on. It turned out that the thermostat setting was too high and it was maintaining the temperature within the range of the otter switch. You have told us you have tested the thermostat(s) but not what the operating temperature is. Maybe try another thermostat with a lower setting?

Keep buggering on and keep us informed!!

[mgcjag]

Hi Paul...what car are you working on here.....you mention S2 waterpump pulley and have a new 3.8 header tank but your signatures says S1......Steve

[paulsco]

Steve,

It is a 65 Series One 4.2.

The reason for Series Two pulleys is they are single V, where as the Series One is double V.
I needed single V to run my air conditioning compressor.

Paul

[paulsco]

Mike,

You are right; I did feel the radiator core temperature when the fan was running, but also when it was off.

I am still trying to get hold of a suitable temperature tester, but the problem remains that the otter switch has not got cool enough to switch off the fan.

As for the thermostat, yes again I was unable to check the actual temperature, just that it worked.

I will follow your suggestion once I have obtained a tester.

I was just hoping after all these changes that I would have solved the problem

Paul

[mgcjag]

Hi Paul...plenty available....you do need one https://uk.farnell.com/multicomp-pro/mp ... -31Aug2020

[PeterCrespin]

I was just hoping after all these changes that I would have solved the problem

Paul

You have.

You are putting a modified (AC condenser) system through a harsh test and it is not boiling over. Almost every other driving scenario will stress the cooling system less. The radiator is more efficient the hotter it gets and I would be surprised if you see a 10C delta between in/out temps. When measuring temps, for consistency I'd use a bit of masking tape on the manifold next to the temp sender, next to the inlet hose tank connection and next to the outlet hose connection. The absolute temp is less important if you're comparing at different points on the same system.

The narrow bypass hose from the manifold to the right rad tank should get hot before the main hose to the header tank.

Assuming they are the right length/fit, try repeating the idle test with your lower temp cap(s). If the result is the same with a 10 lb, 7lb or 3 lb cap compared to your 13lb cap you know you've got a safety margin.

Does your fan fit closely in the shroud hole, not too far forward or back? Is the diameter close? Is the shroud sealed to the core closely with a narrow strip of foam?

[paulsco]

Thank you Peter, I will try your suggestions.

Radiator cowl is standard and sealed to the radiator with strips of foam.

I will check how close the fan is to the radiator, but from memory it is as close as I could safely get.

It is clear that I am working in the dark without temperature tester, so I will get one before going much further.

The masking tape seems a good idea.

The first picture is with the original fan.







Thanks again,
Paul

[mtnjag]

You want the fan at the outlet hole of the shroud, not tight to the rad. If it had individual blades rule is the blades should be about 1/2 outside the shroud Outlet hole.

Your coolcats fan position looks about like mine and i cool nicely. A little back into the opening would be better. The coolcats has an integral shroud to the blades like a lot of electric fans but you still want it at the outlet when a shroud Is fitted for optimum performance.

Did you pickup some stick-on temp strips from Coolcats?

[mtnjag]

To get a good accurate actual coolant temp i take the probe from my digital VOM and slip it under the outlet hose up INTO the coolant flow at the thermostat and reclamp the hose. My meter has a wire sized probe and does not result in a leak. You must of course confirm the accuracy. Test it on your stove with boiling water. If you have a secondary thermometer all the better. Correct for altitude.

[mtnjag]

My error. The Coolcats fan does not have the integral shroud. Was just cleaning up some oil drips and looked at my fan.

[malcolm]

I'm no technical Guru, but I can't help thinking there is something more basic, and maybe more simple, going on here. If the fan goes on, and is the right way round, and if the water is circulating, it should be o.k surely?

[paulsco]

Hi Layne,

I was thinking you must have had a different version to me as mine is just a multi blade fan.

I didn’t get any temperature strips when I got mine from Coolcat.

I have ordered a temperature tester which should show up later today, but I currently have a leek from my otter switch gasket, so I have drained down the system to fix this.
My thermostat joint is also leaking a little, so while I am at it I will fix that as well and take the opportunity to check the temperature the thermostat opens at while I am there.

Hi Malcolm,

I agree, but why is it getting so hot and why is it not cooling down enough to turn off the fan??
Once I can check the temperatures correctly, perhaps I will have a better idea of what is happening.
I am planning to have another look at the ignition; perhaps 8 degrees is not enough and I should try 10 degrees??

Paul

[1954Etype]

Paul,

while you have the Otter switch out, check the temperature range of that as well. Might not be switching off at the correct temperature.

[mgcjag]

Hi Paul...i would have a really good look at the thermostat and its houseing....you did dismiss the actual size of the stat and its houseing quite quickley when we know that its a bit of a minefield getin the correct set up....Steve

[malcolm]

Paul, I might be wrong but I can't imagine that going from 8 btdc to 10 will make any difference. That's what I meant by something more basic. For example, as Steve said, is the thermostat allowing the water to circulate? Is anything else stopping it? I'd concentrate on basics; is water going round everywhere, is air blowing on rad.
BTW, if I leave my car ticking over, it always gets hot although the fans do bring it down after a while, but when driving it always stays cool. Are you just cooking it in the garage?
Forgive my lack of knowledge, but I do believe in KISS

[mtnjag]

Hi Paul,

I have run my 3.8 down to 4 degrees when chasing a detonation issue. It did not overheat so an advance of 8 degrees should not be a problem in that regard, as long as it is actually 8 degrees and something else in the timing is not going on.

Sorry, didn't mean to imply the fan came with the temp strips. You need to buy them separate. I think they're US$2.50 per strip. You stick them in a location and leave them.

Your fan motor looks exactly like mine and from what I can see of your blades they also look like mine, not counting but I think I have 7 skinny blades with NO integral should. Sorry, I corrected myself a couple posts down after I made the statement on the blade should in error.

Don't know what kind of temp tester you are getting but if its an IR be aware it won't give you coolant temp unless it's on the coolant, and then might sense any steam. It will give you surface temps and is handy for seeing differentials. Can be a little scary at some locations.

Gotta get a probe in the Coolant FLOW to actually get coolant temp.

Layne

[paulsco]

I have to admit that I haven’t approached this in a methodical way and have made several schoolboy errors.

I have replaced many items at the same time as it is a pain to keep draining down the system and refilling it again each time a change is made, but in summery I have replaced or tested:

Header tank.

Smaller water pump pulley.

Tested and used two thermostats.

Tried four otter switches, all new or very recent. Two Mitsubishi type and two original type otter.

Fitted a relay to the fan motor.

Tried a 4lbs, 7lbs and 13lbs radiator cap.

Substituted the temperature gauge from my 340 (no difference).

Substituted the voltage regulator for the one in my 340 (no difference).


None of the above has made a difference as far as the fan staying on is concerned.

When trying the 4lbs cap it puked out water, but with hindsight, this was because of over filling.

I have obtained an infrared temperature gun, but frankly the results were illogical and confusing.

What I did establish is that the engine is not overheating. It gets to about 100C on the gauge and the fan kicks in and draws the temperature down by about 10 degrees,

The indicated temperature is still suspect, but all that is left is the sender, which I put in as part of my rebuild. I intend to replace it.

An example of my temperature readings that make no sense to me are (with masking tape targets).

Gauge temperature 100C

Manifold temp 60C

Bypass 62C (this is with the correct type stat, 74C).

Rad top right 65C

Rad bottom right 80C

Rad top left 68C

These are of course outside temperatures not water temperatures, which as has been discussed would be different.

Perhaps my tester is not as accurate as is claimed.

The plus is the engine on a 7lbs cap is not overheating, but the fan continues to run despite this.

The radiator matrix is warm to the touch, but the side tanks and header tank are hotter (but not too hot to touch).

I cannot see how four otter switches could be faulty??

I am going to see how it behaves on the road and take it from there.

Thank you all for taking the time to provide advice, it is much appreciated.

Paul

[mgcjag]

Hi Paul....have you considered an adjustable thermostat for the fans.......Steve