When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I might be off base, but I'm wondering which direction your t-stat is oriented? It's rare, and odd, but I seem to recall a backwards t-stat would pull a vacuum on the hoses like that in older cars. It's been a really long time since I saw one do that tho, so I could be misremembering, just something to check
I might be off base, but I'm wondering which direction your t-stat is oriented? It's rare, and odd, but I seem to recall a backwards t-stat would pull a vacuum on the hoses like that in older cars. It's been a really long time since I saw one do that tho, so I could be misremembering, just something to check
I normally take pictures of these things for future reference, but apparently not this time. I did look several times to make sure I was installing it the right way. Spring side(temp rating) towards engine with the bleeder hole up, looking in the straight end you can see the curved crown end. I have a new expansion tank cap coming tomorrow and if that doesn't help(I suspect it won't) I will be taking the thermostat out and running it without it to see if it's something else.
Yeah, its a defective cap. The cap is designed to vent pressure when the temperature causes the pressure to exceed 140kpa, and allow air back in when closed. So its a bit of a one way valve. Yours is apparently not allowing air back in. BTW, I do recommend runnnig the cap one full turn loose from full tight so the system does not build pressure. The pressure raises the boiling point about 10 degrees but also raises the probability of a hose, radiator end tank, or overflow tank cracking about 75%. It does not affect the cooling capacity of the system at all and prevents almost all blown hoses, cracked tanks, and other leaks. Plus, it will eliminate your collapsed hose issue.
Yeah, its a defective cap. The cap is designed to vent pressure when the temperature causes the pressure to exceed 140kpa, and allow air back in when closed. So its a bit of a one way valve. Yours is apparently not allowing air back in. BTW, I do recommend runnnig the cap one full turn loose from full tight so the system does not build pressure. The pressure raises the boiling point about 10 degrees but also raises the probability of a hose, radiator end tank, or overflow tank cracking about 75%. It does not affect the cooling capacity of the system at all and prevents almost all blown hoses, cracked tanks, and other leaks. Plus, it will eliminate your collapsed hose issue.
Unless you live at elevation as the cap loose over 90-95ish degrees will cause the truck to boil over when you turn it off...I have to tighten caps in both discos during the summer and loosen them each fall.
Unless you live at elevation as the cap loose over 90-95ish degrees will cause the truck to boil over when you turn it off...I have to tighten caps in both discos during the summer and loosen them each fall.
That has not been my experience. Coolant and engine at less than 190 at shutdown should not cause boil over. There is nothing to add additional heat. Now boiling point does DECREASE at elevation, at 5000 ft water drops to 203 degrees boiling.
New cap showed up yesterday but I wanted to wait until it cooled off completely to record another ride. Running the old cap (Britpart PCD000070 sold by Proper Spec on Amazon Feb 2019) 1/4 turn loose kept the upper hose full of coolant and not sucking flat when parked/cooled off. The new cap I just ordered is a Gates 31331, measuring from the flat seal to the orings is shorter than the Britpart one. The orings being higher up would act similar to having the cap loosened off? I wonder which one is the correct measurement? I guess my next move is to remove the thermostat and run it to get a baseline temp to see if something else is wrong... I'm just not getting the magical temp reduction that everyone else seems to be getting.
For some comparisons:
Clutch fan, 180F soft spring Factory thermostat
Ford Fusion E-Fan, Factory Thermostat
Ford Fusion E-Fan, Inline mod, Old Britpart cap loosened 1/4 turn
Temps went down significantly when I changed from the Hayden 2781 standard duty to the 2991 severe duty.
- Turner 4.6 (3 years old)
- Factory water pump (installed with the Turner engine)
- Nissen radiator (few weeks old)
- Idler, pulley, belt (one year old)
- Pentosin Pentofrost SF
- Extinct Inline thermostat
When I had the Hayden 2781, and even with a new Nissens radiator, I was seeing up to 215-deg F when going up gradients.
Now, with the Hayden 2991 @ 82-deg ambient and air-con turned on..... I am seeing 174 to 188-deg highway, 194-deg climbing. It did go up to 206-deg when I climbed to a top of a mountain and idled for a couple of mins, then started dropping quickly.
The DCC fan controller is set for a 180F thermostat as designated by the manufacturer, who recommends not setting to a different setting other than matching the thermostat rating. The test route is a light duty route on primary and secondary roads with 2 short to moderately long hills [23.3mi, 248-436ft elevation, average speed 33mph, max speed 60mph, 44mins]. Outside temps range from about 78-88F, but I haven't noticed any correlation since on almost every run I have crossed 200F.
It's just discouraging since everything I have done there is a majority of people that have seen fantastic results with. So far my best results have been with the stock thermostat and stock clutch fan...
....I just gotta find my Needle in the Hayfield...
Last edited by Sandman614; Jul 15, 2022 at 01:01 PM.
@Sandman614 If it helps most clutch fans engage at about 170 air temp - 180 to 190 engine temp. They will generally run for about 20 Deg engine temp drop, depending on conditions.
Can you test the temp probe for the DCC - it could be faulty
My Disco will get warm going up the local hills about 197 in those temps but we have 5 to 6% grades around here and they are short 5 or 10 minutes at 30 mph, but i run pretty low rpm on those maybe 1800 to 2000.
