Mpg tanked again

[InlineDave87]

I have been noticing my economy getting worse again. Yesterday i did a rough calculation and got 12.4 mpg on the highway. But we did have freezing temps and i had a decent head wind. My radiator is a two row instead of the standard single row. I dont think my truck ever got up to temp cause i was freezing even with my heater on, heater wasnt doing anything. No check engine lights, i just had to redo brakes all the way around. Im thinking i need to seafoam fog it to clear out the intake and exhaust. Maybe pull plugs and see if shes ready for a tune up?

 

[sixtseventwo4d]

First thing I would want to check is the thermostat. The engine has to warm up. Your tire pressure probably dropped dramatically when the temps did.

 

[63 Sprint]

Definitely sounds like a thermostat.
If you’re able, find the Motorcraft OEM 192 deg F. Thermostat.

I’m not sure if you remember the dilemma I’ve had with aftermarket thermostats. They would go bad in less than a year. I’ve tried premium grade NAPA brand and others. They all lived a short life. When they went bad, the engine never reached temperature. So far the Motorcraft OEM thermostat is still working fine.

Here is the link:

https://www.fordsix.com/threads/going-through-one-thermostat-a-year.84964/#post-686808

 

[Frank]

Yeah Dave, if it's running cold the ECM is not calculating. Also, mileage is going to drop in cold air. I say this because you hardly ever get any, but the density difference is 10% and more. Tire pressure is down as much as 10% and more also. . (You guys got a pretty good blast that far south!)
I got a Flowkooler T'stat directly from them. This winter is the FIRST time the '90 has ever not run cold since I've had it. (Big radiator) . Regret not getting a quality one years ago. VERY pleased with it, no comparison to cheepies.

FlowKooler Hi Flow Water Pumps

FlowKooler pumps patented impeller designs help stop engines from overheating and reduces engine temperature up to 30 degrees by doubling the flow of coolant and building system pressure.

flowkoolerwaterpumps.com

 

[Soldmy66]

During winter driving when the temperature is very low, some people block/partially block their radiator with coroplast (corrugated plastic sheets) to reduce airflow.

 

[PSIG]

You could have a water tanker truck for a radiator, and it should still warm to normal temperature for proper fueling and heater operation. Most thermostats are designed to fail open.

I have had good results with Motorad Ultrastat version. Quality stainless, with jiggle valve for purging air pockets - important to ensure the thermostat and sensors are in coolant to operate properly. Motorcraft has been a good one, although I hear they changed management hands lately, and may need re-evaluation?

More Information for MOTORAD 5244192

 

[comet6]

You could have a water tanker truck for a radiator, and it should still warm to normal temperature for proper fueling and heater operation. Most thermostats are designed to fail open.

I have had good results with Motorad Ultrastat version. Quality stainless, with jiggle valve for purging air pockets - important to ensure the thermostat and sensors are in coolant to operate properly. Motorcraft has been a good one, although I hear they changed management hands lately, and may need re-evaluation?

More Information for MOTORAD 5244192

I've been burned twice on economy thermostats. One would swing from 215 then plummet to 160 and slowly start regulating. Terrible control. That is going to be exacerbated by low coolant temp inrush. It's easy enough to swap.

 

[PSIG]

The Ultrastat isn't an economy unit, and I currently use them as they are high-flow, with bleed valve, and the temperatures are stable without spiking or bouncing. The real-time engine temperatures are logged in the data systems I tune, so I've seen plenty of brands in action. Somewhat better than previous Motorcraft RT-1139 versions at the same price, but those were also better than many, although I haven't seen current production. The high-end Stant SuperStat also does pretty well.

 

[63 Sprint]

PSIG,
Your post claims that the Motorad and some other thermostats are somewhat better than the Motorcraft. This might be true. But, without testing and documentation while running them on a 240 or 300, statement’s bare little weight.

The thread starter has a 4.9 EFI engine in the truck. This engine falls in the category of the 240/300 sixes. This is what we are focusing on. We are not focusing on any other makes and models.

I have experimented with different thermostats in a 300 engine for over three years and have proof that two NAPA Echlin premium branded thermostats started acting up within less than a six months after their install. Autozone premium branded thermostat started acting up in less than six months. Advance Auto premium thermostat started acting up in less than six months. All four thermostats failed by not keeping the coolant to operating temperature in less than a year. Every thermostat was opening too soon and the engine ran cold. When those thermostats were removed, everyone was in the closed position. They were not hung open.

The Motorcraft 192 F. Thermostat. Part # XR3Z-8575-BA Is the Motorcraft RT-1139 that you’re referring to is the only thermostat that is holding up well in my 300 engine. There have been no changes in operating temperature. It’s been very stable. It’s been installed on May 31st, 2023. Almost eight months and no signs of acting up. And, if for whatever reason, if the thermostat starts acting up, it will be documented.

Here is a picture of the Motorcraft XR3Z-8575-BA (RT-1139)

 

[InlineDave87]

Yea i need to get a temp gun to verify what my truck is doing. Normally my truck when at a light, the needle will get between N and O. Once im driving it will drop just bellow the N. On that day it barely made it halfway to the N and that was me going 70 trying to push her harder. Also found out my speedo is reading 5 mph over. Found a youtube video where a guy explains where you can do some math to get a code to recalibrate the speedo. I may just opt for going a size larger tire since i have new to me wheels too. I found a deal on the style that everyone likes for like $200 and they just need some cleaning up. I plan on taking these old ones and cleaning them up, paint them and sell them.

 

[63 Sprint]

Yea i need to get a temp gun to verify what my truck is doing. Normally my truck when at a light, the needle will get between N and O. Once im driving it will drop just bellow the N. On that day it barely made it halfway to the N and that was me going 70 trying to push her harder.

What you just described are symptoms that I’ve experienced when thermostats start going bad.

It starts out as gradual fluctuations in temperature then gradually gets worse until the thermostat is not able to maintain proper engine operating temperature.

In my case a cool running engine temperature of around 140 degrees F.

 

[Frank]

Yea i need to get a temp gun to verify what my truck is doing. Normally my truck when at a light, the needle will get between N and O. Once im driving it will drop just bellow the N. On that day it barely made it halfway to the N and that was me going 70 trying to push her harder. Also found out my speedo is reading 5 mph over. Found a youtube video where a guy explains where you can do some math to get a code to recalibrate the speedo. I may just opt for going a size larger tire since i have new to me wheels too. I found a deal on the style that everyone likes for like $200 and they just need some cleaning up. I plan on taking these old ones and cleaning them up, paint them and sell them.

If the gauge and heater say "cold", then the gun will tell you the same.
If your tires are worn out the speedo will be off by that much at high speed. New tires will bring it back down.
However, if you're planning a rim change, I'm in the market for stock rims for a '79. Not mag, old-school style. What are yours?

 

[sixtseventwo4d]

I believe something to do with some thermostat failure ON these engines and possibly others is that the thermostat is mounted directly against the housing which is insulated between the head with a gasket. Any voltages that find their way into the coolant will have to pass by this insulated area. Some of this (static) voltage is induced by the cold air traveling through the dry, EFI intake. A remedy could be as simple as an additional ground from the head to the block; along with a good antifreeze mix of course. I would go 8 but a 10 or 12-gauge wire would be sufficient.

 

[63 Sprint]

Good information sixtseventwo4d, thanks for posting.

My F150 had grounding issues. Upgraded the grounds under the hood. Before, the wiper motor would just quit running and dash lights would dim. One thing I was concerned about was having electric current passing through the coolant heated Offenhauser C manifold. Reworking the grounds most likely helped reducing electrical current passing through the manifold.

I agree keeping coolant clean. Broken down coolant can be corrosive to cast aluminum.

 

[63 Sprint]

I just was thinking about the thermostat housing that’s used on the 1989 4.9 EFI. I’m not sure if all thermostats mount the same on other 240, 300 and 4.9 EFI engines.

The 1989 thermostat housing has a recess on the flange and the thermostat fits in the recess and sits slightly proud above the flange face. A gasket is used to fit over the the thermostat that’s recessed in the housing flange. When the housing is installed to the cylinder head, and torqued properly, the gasket presses the thermostat against the housing.

If the thermostat has good contact against a clean thermostat housing, and the bolts & lock washers have good contact to the housing and head, the thermostat might be protected from excessive exposure from electrical current passing through the thermostat.

 

[PSIG]

Your post claims that the Motorad and some other thermostats are somewhat better than the Motorcraft. This might be true. But, without testing and documentation while running them on a 240 or 300, statement’s bare little weight.

The thread starter has a 4.9 EFI engine in the truck. This engine falls in the category of the 240/300 sixes. This is what we are focusing on. We are not focusing on any other makes and models.

This is an '86 F-150 4.9 twin turbo I did for a client early in the pandemic, that used the Ultrastat kit with housing and Ultrastat thermostat. You can see the very stable temperature logged across the 28 minute log. You can see the hard accel/decel in the blue rpm/s trace at the bottom, so you know it wasn't just loafing along. I require boost conversions to have high-flow thermostats installed to help stabilize temperatures for effective tuning.

That said, the thermostats are made with all the same parts, in different diameters and ratings, so the functional guts in a Ford 300 thermostat are the same as one for a Buick - just a different housing to fit. The characteristics of a certain thermostat brand and model tend to be very similar from one application or engine to another, which is why I have seen many Motorcraft, MotoRad and others. Why would the 240 or 300 be a special case? Not being snarky - that's a sincere question.




[EDIT] BTW, no failures of any of them, including this one, that I've heard of. Sounds like NAPA and Advance are ones to avoid.

Also, it would appear any stray electrical current in the engine transferred to the coolant will bypass the thermostat through the housing and housing bolts. So while the thermostat may be affected by electrolysis like any other part, it nor the gasket would create a 'blockage' for electrical current at the housing.

 

[63 Sprint]

This is an '86 F-150 4.9 twin turbo I did for a client early in the pandemic, that used the Ultrastat kit with housing and Ultrastat thermostat. You can see the very stable temperature logged across the 28 minute log. You can see the hard accel/decel in the blue rpm/s trace at the bottom, so you know it wasn't just loafing along. I require boost conversions to have high-flow thermostats installed to help stabilize temperatures for effective tuning.

Good knowing that other thermostats are stable. You logged it for 28 minutes. The thermostat that was used in the test held up well to abuse. This is what people need that stress their engine. Thanks for posting the info.

But a concern is, how will a certain brand thermostat hold up long term? The NAPA, Autozone and Advance Auto thermostats were fine when first installed. Over time, they started acting up. My experience is I will not choose any of the three I listed. The Motorcraft thermostat I listed in the earlier post is holding up fine. It has not shown any unusual operating characteristics like the others tested. The Motorcraft thermostat is very stable. It’s doing its job as intended. It’s been a proven thermostat. But as we all know, there could be a bad apple in the bunch.

It takes time to weed out the bad thermostats. The only thing we can hope for is to find thermostats that will hold up and give long reliable service.

That said, the thermostats are made with all the same parts, in different diameters and ratings, so the functional guts in a Ford 300 thermostat are the same as one for a Buick - just a different housing to fit. The characteristics of a certain thermostat brand and model tend to be very similar from one application or engine to another, which is why I have seen many Motorcraft, MotoRad and others.

It’s like choosing which fruit to have during lunch. I happen to like apples and oranges. The good thing is, there is more than one choice available.

Sounds like NAPA and Advance are ones to avoid.

I totally agree, these brands failed in a short time. (You left out Autozone brand, it’s easy to do) I cannot recommend these thermostats to anyone.

Also, it would appear any stray electrical current in the engine transferred to the coolant will bypass the thermostat through the housing and housing bolts. So while the thermostat may be affected by electrolysis like any other part, it nor the gasket would create a 'blockage' for electrical current at the housing.

Lots don’t understand the importance of proper grounding. Lots of auto manufacturers took shortcuts and grounding issues normally manifest years later.

It’s amazing how fast damage can happen. Electrical current flowing through engine parts is known to be a silent killer.
Changing coolant regularly can help prevent or reduce internal damage in engine cooling systems.

 

[InlineDave87]

Did the same trip today. Engine temp was back up but still not sure exactly what it was. Still only got 13.3 mpg… back to the drawing board.

 

[Rinke]

And don't forget to check a t stat in boiling water before installing. I didn't and almost blew the head gasket since it was stuck in the closed position. Fyi it was brand new out of the box. Make unknown.

 

[63 Sprint]

Did the same trip today. Engine temp was back up bust still not sure exactly what it was. Still only got 13.3 mpg… back to the drawing board.

Wonder if the gas has an ethanol content of over 10%. It’s been known that some places in NC shown over 20% at pumps.