Hello All,
So I have been investigating my rebuilt 351W 2v engine with A/C and an automatic FMX for some Time now to track down why it steadily overheats when sitting.
The Things I’ve Done:
-Rebuilt Engine (head gaskets re-replaced due to a suspicion that they were bad)
-New Aluminum 3 row radiator installed
-New thermostat (180F - there have been more than 10 thermostats put in over the time I’ve been having the problem so I definitely made sure it was in correctly and it opens (the gauge also shows when it open)
-New water pump correct for the year
-Heater core replaced along with water inlet valve
-New hoses
-Sending unit tested and gives proper ohms readings (400 ohms when it was in 35F degree temps and lowers to about 15 ohms when its in boiling water so it works)
-I tested the gauge to see if it worked by grounding it out and it pegged to the hot side and then I tested the calibration by adding a 22ohm resistor to the circuit and it brought the needle just shy of the 1/2 way point (I read this is a mustang temp gauge forum for vintage mustangs so I tested it here))
-Added a new air filter
-All new air-conditioning components
-Repainted 7 blade fan
-New fan clutch
-Fan shroud
When the car gets to operating temp the needle sits above the halfway point about 3/4 of the way on the gauge
I took temperature readings with an infrared temp gun today when it was 55 degrees outside (with an aluminum radiator)
Cold temperatures:
Intake manifold behind thermostat housing: 47F
Hose at upper radiator: 56.0F
Radiator before hose upper: 56.0F
Lower hose: 45F
Lower radiator before hose: 50.9F
Hot temperatures after idling in park for about
Intake manifold behind thermostat housing: 188-219F (this value fluctuated which I attribute to the thermostats opening and closing?)
Hose at upper radiator: 195F
Radiator before hose upper: 155-160F
Lower hose: 151-157F
Lower radiator before hose: 152-163F
The radiator side facing the front bumper of the car read about 130F and the back side near the fan read about 212F
After about 25 minutes these values raised higher with the lower temperatures reading around 165ish and the upper reading 190ish and the temp gauge creeped up to an 1/8 of an inch below the start of the red
The idle speed for the car with the choke was 1200rpm and when the choke was disengaged and the car completely warmed up it was 700-800rpm
I then went onto WCCC and looked at the pulleys for the water pump as at this point I feel as though I’ve tried everything and the car doesn’t run rough at all and I’m running out of ideas. I’ve taken it into a mechanic and they can’t find anything wrong with the car but my values and what I see do concern me as the car gauge is accurate and should creep up that much just sitting. There seemed to be a listing for a non A/C 351W that had a diameter of 6 and 7/16 inches. The other pulley was 5 and 7/8 inches. I then went and measured my pulley, without removing the fan so I had to estimate a little, but my reading looked above 5 and 7/8 inches and looked more like 6 and 7/16 inches.
Could this pulley size difference cause that much of an increase in temperature? Could it cause a difference in where the fan sits? Is it possible the pulley is what’s causing this problem? It seems to me the coolant is circulating, but if the pulley affects the fan spacing it would create an airflow issue which could cause this, right? Would this size difference really cause this?
Thank you for any ideas here. I’ve been at this since 2016 and still haven’t located the problem yet so any help would be more than appreciated!
Bigger pulley = less flow. But the numbers don’t look all that high to me. But I am no expert. Idling will create a hotter engine then when moving, Any idea how hot it gets when outside temps are in the 70’s or higher?
When it gets warmer outside the temps are hotter on the gauge than when its colder. So a 3/4 reading for “normal at cold” bumps up a bit and is usually just below 1/8 from the red. In general though it exhibits the same behavior in hot and cold climates. While driving the car is 100% fine its always when it starts to sit or after driving and stopping at a red light it starts to climb (typically fairly quickly).
Hi,
After reading your post, my first initial thought is the head gaskets. You mention they have been replaced twice. It’s very easy to put them on the wrong way. Misrouting of coolant from the block to the cylinder heads due to water passage blockage at the wrong end of the heads could very well cause overheating. Another thought, did the block get throughly cleaned when it was rebuilt?
I don’t believe the pulley would have anything to do with it, but that is only my opinion.
It looks like all of your infrared temperature readings are right where they should be. So my question is: is your concern revolving around the gauge reading? These can be changed substantially by adjusting the constant voltage regulator on the back of the dash cluster. Before you do so, I have a question:
Is your fuel gauge reading accurately at 1/4 tank, or is it higher than it should be? If the latter, the CVR definitely needs adjusting. There’s a small stud or screw on the back side that you can turn, which changes the voltage to the gauges. You can change it up to about half of a gauge sweep!
With the exception of the fuel gauge, the other gauges are best used as indicators of unusual readings from normally expected, whatever that is. If your temp gauge reads 3/4 when running around town, then that is normal. Deviations from that reading are indications of something going on. In other words, precise calibration of these gauges is not recommended. You can “calibrate” the fuel gauge to read accurately if you know exactly how much gas is in the car and adjusting the CVR for the gas gauge to read that amount (I recommend 1/4 tank).
I don’t usually let my tank get down to 1/4 very often ( I like to keep it in the upper 1/2), but the times that it has been down in that area it takes right around 15 gallons to fill it back up. It’s definitely not accurate between the markers but for each tick mark I would say it is fairly accurate. I will definitely look into that CVR to exactly how accurate the gauge really is. I only know it takes roughly 15 to fill it back up.
I also read on a vintage chevy forum that having an increase in pulley size would cause the water pump to spin slower. The guy in the post had a 6.5 in diameter aftermarket pulley and the original was 6 in and he said that resulted in the pump spinning 30% slower (not sure about his formula or how you calculate that). The difference between the Ford A/C and non A/C is 0.59 in in the diameter which is about the same half inch discrepancy which may account for the overheating at idle speeds when the fan is most needed. Driving the car has no issues and its only when stopped. I definitely want to try your suggestion with the gas tank and seeing where it should read. Thank you
Have you tried a high quality mechanical water temperature gauge in the intake manifold where the electric sender is attached to see what the actual temperature of the water is?
The temperatures you have seen with the heat gun seem pretty reasonable, is the car acting like it is overheating?
I’ve only taken measurements with a heat gun and it hasn’t been acting differently. Its just very concerning to watch the needle creep up when stopped and sit right on the line (sometimes crossover over). It’s more like a peace of mind thing. Before the rebuild happened I would drive the car and the needle never strayed from the 3/4 position. The car runs infinitely better than it did before the rebuild now as well which is why the gauge is concerning to me. The block was cleaned and then checked for leaks which it didn’t have any of.
I might see if a lower temp thermostat changes the reading you see. You may not want to run at 165F for performance, but it should get you around the 1/2 way mark on your temp gauge. This should at least tell you if the gauge is the problem or you are really running hot for minimal cost.
I installed a flowkooler water pump when I went back to a 180F thermostat and the 351W in my 70 Cougar ran cooler/more consistent with that. I’ve also seen wetting agents added (typically used in water only systems - but also used in coolant).
I see you tested the sender but you need to find an original Ford sender. Like the repop fuel senders the linearity of the resistance is usually off at one resistance end (gas gauge shows lower than it is). If a Ford sensor doesn’t solve it put in a high volume water pump. Is the fan about 1 inch from the radiator? Spring in the lower hose? Thermostatic clutch?
I installed an original three groove crank pump pulley as well as an original water pump pulley (the crank pulley was aftermarket and off by a little but and the water pump pulley was for a non AC car. The curious thing is that now that all of the pulleys are the correct size the belts that are recommended for the car actually don’t fit (too short) so I had to play with a few sizes to dial it in (either 1 or two sizes above depending on the belt). The needle in the dash now sits just above the 1/2 way mark for a while, but once the car starts driving and sits at a red light long enough (city traffic), the needle again starts to creep up until its almost at the red. For me that’s a lot of movement just for sitting. The car needle drops a little bit once the car is moving again (above 30 mph), but it never goes back to 1/2. It usually will drop 2-3mm on the gauge. The fan clutch is thermostatic and the reproduction from WCCC and the fan sits 1 inch from the radiator in a fan shroud. The thermostat is a 180 and opens when the engine reaches that temperature.
When you are going down the road, the fan clutch and shroud are no longer a part of the equation. The ram air effect is pushing more air trough the radiator than the fan ever could. Since it is not cooling down then, all signs point to the radiator itself not flowing enough water (the water pump will be spinning fast enough at that point to be somewhat irrelevant). I would get an original 24" 3 or 4 core copper / brass radiator and I thin it will cure the problems. Take a look at the size of the radiator hoses. They are huge in comparison to a garden hose. They are that large because the amount of water moving through the system is huge. Most likely the aluminum radiator is restricting the flow. Keep in mind that the 24" stock 2 core was adequate to cool off even the 428CJ and horse power equals heat.
One other possibility is the thermostat. The parts store Stant is too small and restricts flow. Get a Robert Shaw type (Mr. Gasket also offer their version) a 190 degree is a good choice for most engines.
I’ll start by trying the higher flow thermostat first as buying a third radiator would be quite expensive. Thank you all for the suggestions. They’ve given me quite a few things to look at
I also have 351W-2V, however no A/C = smaller 20" rad - but I think what follows would work just as well with bigger 24" rad.
When I bought my car it was behaving like yours i.e. needle rising to red in slow traffic. To resolve, I increased air flow through the rad during idling by pulling the fan toward the engine to make it sit about ½ in shroud and ½ ahead of it… then the shroud could truly act a funnel in which air flow through rad was maximized (I could feel it strong just checking it with my hand in front of rad at idle).
Since I do not have a fan clutch (just a direct fan - 7 blades as yours), I moved it simply by removing the spacer that was put there instead of the missing fan clutch. I know a direct fan eats some power but my car did not have fan clutch in the first place and is not competition anyway!
That alone improved it quite a bit… it still needed to be shifted in neutral position during long standing at traffic lights (to gain air flow from higher 900 rpm at idle), but I could enjoy my car with no fear to stall and/or overheat no matter what.
The following year I replaced my 2 row stock rad with a similar one, but 3 rows… and that further improved it well enough to re-install the specified 195°F thermostat while never climbing to red anymore.
Obviously, that would not have worked if I had been missing water flow, but I knew it was OK since the needle was returning to its ½ scale position when driven for ± 10 minutes at ± 50-60 MPH after a stupid episode of “red traffic climb”!
Hoping this is helpful, even if just a little… and good luck fixing this very frustrating issue!