Coolant pressure
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Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 931
From: Fort Worth, TX
Coolant pressure
Ever since replacing the heads, I've typically seen coolant pressures in the 10-12 range at operating temps at highway speeds. I've noticed it going up a point or two after an extended WOT blast, but it normally comes back down after 10-15 minutes of cruising.
For the last couple of weeks the numbers have been going up, and strangely, or coincidently, it started immediately after replacing the oil pressure regulator. Since the replacement, I've seen numbers as high as 14. Historically, in the morning at cold start, the pressure gauge shows 0, but lately is been 6, or 8, or even 17 one morning. That same day the gauge showed 30 psi and I ordered a new sensor.
I replaced the sensor this morning before starting the engine. There was still pressure in the system; air rushed out when removing the old sensor. By the time I drove 3 miles to the dump, it was already at 13 psi with coolant and oil temps in the 180's. Drove eight miles across town to the bank, and half way back home it was up to 16 with coolant and oil temps in the low to mid 190's.
How is this even possible with o-ringed heads and all the prep I did to the decks? Talk about frustrating.
For the last couple of weeks the numbers have been going up, and strangely, or coincidently, it started immediately after replacing the oil pressure regulator. Since the replacement, I've seen numbers as high as 14. Historically, in the morning at cold start, the pressure gauge shows 0, but lately is been 6, or 8, or even 17 one morning. That same day the gauge showed 30 psi and I ordered a new sensor.
I replaced the sensor this morning before starting the engine. There was still pressure in the system; air rushed out when removing the old sensor. By the time I drove 3 miles to the dump, it was already at 13 psi with coolant and oil temps in the 180's. Drove eight miles across town to the bank, and half way back home it was up to 16 with coolant and oil temps in the low to mid 190's.
How is this even possible with o-ringed heads and all the prep I did to the decks? Talk about frustrating.
Hotshot
Joined: Dec 2014
Posts: 17,823
Likes: 3,101
From: Jersey Shore
Knowing how detailed you are, I would not expect something glaringly missed. I know with my ambient temperature changing so much lately, I can find residual pressure on some days.
I don't remember all your details. Was the head gasket used as recommended by the head supplier?
I don't remember all your details. Was the head gasket used as recommended by the head supplier?
Thread Starter
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Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 931
From: Fort Worth, TX
The HG's are Fel-Pro. The pressure sensor is threaded into the side of the degas bottle. It is a digital Glow Shift gauge. I have no coolant filter.
https://www.glowshiftdirect.com/10-c...ressure-gauge/
I called Glow Shift and was told that air pressure can build-up in the space between the sensor and the harness plug, throwing off the readings. How that's possible when we're talking about 12 psi is beyond me. Maybe they should ask Ford how they keep the ICP from leaking at 1500 psi. Anyway, I went out and pulled the plug, reinstalled, and pressure was reading 6. Did it again and it read 0. Again and it settled at 43. Then 0. Then 37. Then 0. Then I drove across town and back again, and it never went over 6.
So, in the end, it boils down to a junk gauge. Makes me wonder how accurate my Glow Shift fuel pressure gauge actually is. I now have zero confidence in this brand. I was thinking about converting the coolant pressure sensor over to lpop pressure, but now I think I am in the market for something I can trust.
https://www.glowshiftdirect.com/10-c...ressure-gauge/
I called Glow Shift and was told that air pressure can build-up in the space between the sensor and the harness plug, throwing off the readings. How that's possible when we're talking about 12 psi is beyond me. Maybe they should ask Ford how they keep the ICP from leaking at 1500 psi. Anyway, I went out and pulled the plug, reinstalled, and pressure was reading 6. Did it again and it read 0. Again and it settled at 43. Then 0. Then 37. Then 0. Then I drove across town and back again, and it never went over 6.
So, in the end, it boils down to a junk gauge. Makes me wonder how accurate my Glow Shift fuel pressure gauge actually is. I now have zero confidence in this brand. I was thinking about converting the coolant pressure sensor over to lpop pressure, but now I think I am in the market for something I can trust.
Last edited by Fuzzpuss; Apr 10, 2026 at 11:27 PM.
Cargo Master
Joined: Oct 2018
Posts: 2,808
Likes: 1,895
From: unfortunately Germany
That’s why I asked how and where you measure the pressure.
There’s nothing like a mechanical gauge, like the one I used to have installed. To check the actual pressure and assess your situation, you can simply install a T-fitting in the hose running from the degas bottle to the radiator and attach a mechanical gauge.
I’ve also have Glow Shift gauges installed for about two years now. For that much money, what they’re selling is an absolute joke—I’ve had problems with them from the very beginning.
Their customer service is absolutely terrible.
There’s nothing like a mechanical gauge, like the one I used to have installed. To check the actual pressure and assess your situation, you can simply install a T-fitting in the hose running from the degas bottle to the radiator and attach a mechanical gauge.
I’ve also have Glow Shift gauges installed for about two years now. For that much money, what they’re selling is an absolute joke—I’ve had problems with them from the very beginning.
Their customer service is absolutely terrible.
Hotshot
Joined: Dec 2014
Posts: 17,823
Likes: 3,101
From: Jersey Shore
I asked whether the gasket brand was the one the head manufacturer stated was acceptable.
I've not had any issues with the Glow Shift pressure gauges I installed four years ago. That's a better track record than what I experienced with Isspro. I don't believe Pete ever had issues with them with either his 6.0L or his newer Ram.
Having the pressure reading change when going back and forth, plugging it in and out, sounds more like a poor connection issue since the pressure gauge uses resistance for the readings, just like the Ford sensors. If I had that issue, I would first check the pins, then use something like DeOxIt to clean the contacts. When I installed my three pressure gauges and three temperature gauges, I used a dab of Ford electrical contact grease on them. Most people don't.
GS did have issues with the large-diameter sensors years ago, but I believe they no longer use them, maybe since 2018.
I've not had any issues with the Glow Shift pressure gauges I installed four years ago. That's a better track record than what I experienced with Isspro. I don't believe Pete ever had issues with them with either his 6.0L or his newer Ram.
Having the pressure reading change when going back and forth, plugging it in and out, sounds more like a poor connection issue since the pressure gauge uses resistance for the readings, just like the Ford sensors. If I had that issue, I would first check the pins, then use something like DeOxIt to clean the contacts. When I installed my three pressure gauges and three temperature gauges, I used a dab of Ford electrical contact grease on them. Most people don't.
GS did have issues with the large-diameter sensors years ago, but I believe they no longer use them, maybe since 2018.
Tuned
Joined: Oct 2015
Posts: 392
Likes: 86
From: Roebuck, SC
That’s why I asked how and where you measure the pressure.
There’s nothing like a mechanical gauge, like the one I used to have installed. To check the actual pressure and assess your situation, you can simply install a T-fitting in the hose running from the degas bottle to the radiator and attach a mechanical gauge.
I’ve also have Glow Shift gauges installed for about two years now. For that much money, what they’re selling is an absolute joke—I’ve had problems with them from the very beginning.
Their customer service is absolutely terrible.
There’s nothing like a mechanical gauge, like the one I used to have installed. To check the actual pressure and assess your situation, you can simply install a T-fitting in the hose running from the degas bottle to the radiator and attach a mechanical gauge.
I’ve also have Glow Shift gauges installed for about two years now. For that much money, what they’re selling is an absolute joke—I’ve had problems with them from the very beginning.
Their customer service is absolutely terrible.
It's under the hood so it's only checked every week or so but it works great
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Fleet Owner
Joined: Nov 2003
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I have mine rigged up where I can move the fuel pressure sending unit over to the degas pressure sensor (same brand/model sensor for both fuel pressure and coolant pressure). Whenever I install an electronic pressure sensor, I always also install a port to get a manual reading (just for periodic validation). In past manufacturing jobs, pressure transmitters were notorious for drifting out of calibration (heat, bumps/vibration, age, etc).
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Hotshot
Joined: Dec 2014
Posts: 17,823
Likes: 3,101
From: Jersey Shore
Yep. Me too. I’ve got a very expensive gauge in the lower range that I use for the low pressure cals. It also what I used a long time ago attached in the engine compartment as it has a highest pressure indicator. I didn’t do real time readings while driving, but I could check what the max was.
Laughing Gas
Joined: Aug 2018
Posts: 934
Likes: 248
From: CA
I have a Glowshift pressure on my coolant system also, but mine is tee'd into the degas line between the radiator and degas bottle. I agree with Jack, since you can connect and disconnect the sensor and get different readings, I'd look there. Maybe I missed it, but the the system actually have pressure in it, I mine have you tried to bleed the pressure off with the degas cap and see if it builds again, or goes to 0 with the cap removed?
Fleet Owner
Joined: Nov 2003
Posts: 27,871
Likes: 3,592
Also, you have to be careful with chemical compatibility with glycol systems. Certain butyl rubbers are incompatible with glycol, the fluid can cause them to deteriorate. This an impact the senor's operation. Stainless diaphragms are best in this service (e,g, Quadzilla's fuel pressure sensor).
Last edited by bismic; Apr 11, 2026 at 12:37 PM.
Thread Starter
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Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 931
From: Fort Worth, TX
I haven't had any trouble with their customer service so far, though I would have trouble telling a customer with a straight face that "sometimes air leaks through the sensor, creates pressure under the harness plug, and throws-off the readings". He did send a link to a video which shows how to test the sensor, but there has to be pressure in the system for the third and final test, and they won't just tell you in the video what good and bad readings look like. You have to call customer service for that.
Thread Starter
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Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 931
From: Fort Worth, TX
I asked whether the gasket brand was the one the head manufacturer stated was acceptable.
I've not had any issues with the Glow Shift pressure gauges I installed four years ago. That's a better track record than what I experienced with Isspro. I don't believe Pete ever had issues with them with either his 6.0L or his newer Ram.
Having the pressure reading change when going back and forth, plugging it in and out, sounds more like a poor connection issue since the pressure gauge uses resistance for the readings, just like the Ford sensors. If I had that issue, I would first check the pins, then use something like DeOxIt to clean the contacts. When I installed my three pressure gauges and three temperature gauges, I used a dab of Ford electrical contact grease on them. Most people don't.
GS did have issues with the large-diameter sensors years ago, but I believe they no longer use them, maybe since 2018.
I've not had any issues with the Glow Shift pressure gauges I installed four years ago. That's a better track record than what I experienced with Isspro. I don't believe Pete ever had issues with them with either his 6.0L or his newer Ram.
Having the pressure reading change when going back and forth, plugging it in and out, sounds more like a poor connection issue since the pressure gauge uses resistance for the readings, just like the Ford sensors. If I had that issue, I would first check the pins, then use something like DeOxIt to clean the contacts. When I installed my three pressure gauges and three temperature gauges, I used a dab of Ford electrical contact grease on them. Most people don't.
GS did have issues with the large-diameter sensors years ago, but I believe they no longer use them, maybe since 2018.
I have checked the pins but haven't tried DeOxit. Have to give that a try in a bit. And get some of that XG-12.
Thread Starter
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Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 931
From: Fort Worth, TX
I have a Glowshift pressure on my coolant system also, but mine is tee'd into the degas line between the radiator and degas bottle. I agree with Jack, since you can connect and disconnect the sensor and get different readings, I'd look there. Maybe I missed it, but the the system actually have pressure in it, I mine have you tried to bleed the pressure off with the degas cap and see if it builds again, or goes to 0 with the cap removed?