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#4725161 - 04/12/18 09:05 PM Is This Possible?
CCI Offline

Registered: 07/15/09
Posts: 139
Loc: New Mexico USA
GMC Vortec 5.7, 16 years old, 155K miles.

Coolant has never been changed, system has never been flushed until today.

Could a coolant system flush and fresh coolant make the truck run smoother?

#4725168 - 04/12/18 09:09 PM Re: Is This Possible? [Re: CCI]
BrocLuno Offline

Registered: 09/06/15
Posts: 5621
Loc: Kalifornia Kollective
Maybe, but it must be linked to a previously partially blocked coolant passage ... Hot spot will cause a engine to run odd ...
Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.

#4725176 - 04/12/18 09:13 PM Re: Is This Possible? [Re: CCI]
Lolvoguy Offline

Registered: 02/06/14
Posts: 2393
Loc: Canada
Possible. Especially if the old coolant lost it's pH balance.

Coolant contains additives called buffers that keep it at a neutral pH. When these chemicals become depleted, the pH canít be controlled. This is not a gradual process. The pH rises dramatically in a short period of time the moment the buffers are fully depleted. This is when replacing the coolant at the recommended interval is critical.
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#4725194 - 04/12/18 09:25 PM Re: Is This Possible? [Re: CCI]
gathermewool Offline

Registered: 01/09/09
Posts: 6064
Is it not runn g smoothly now?

#4725205 - 04/12/18 09:39 PM Re: Is This Possible? [Re: CCI]
4WD Online   confused

Registered: 09/21/10
Posts: 6547
Loc: Texas
Original water pump?

#4725238 - 04/12/18 10:29 PM Re: Is This Possible? [Re: CCI]
VeryNoisyPoet Offline

Registered: 12/16/17
Posts: 318
Loc: Massachusetts
Coolant flush can't hurt. especially at that age. May or may not improve the smoothness.

I'd be looking at vacuum lines and intake gaskets. A little pirate air can make a big difference in how nicely an engine runs.
Clean throttle body and idle air control valve (IACV), if present.
If plugs are old, clean, check gaps, and replace if needed.
Run a few tanks of fuel system cleaner and change fuel filter if not done recently.

Are you getting a general roughness, or is there more of a distinct miss under certain conditions?
1998 V70 GLT / 187k miles

"Use yah blinkah!"

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#4725273 - 04/12/18 11:25 PM Re: Is This Possible? [Re: CCI]
Fsharp Offline

Registered: 12/11/15
Posts: 417
Loc: Kentucky
Increased electrical conductivity of old coolant can mess with electrical sensors on your engine. That could be why it runs smoother with the new coolant.

#4725378 - 04/13/18 06:42 AM Re: Is This Possible? [Re: Fsharp]
CCI Offline

Registered: 07/15/09
Posts: 139
Loc: New Mexico USA
Water pump is original, fuel filter and plugs were changed at 120K, bottle of Techron prior to last fill up, truck was running OK for its age. Not my truck, owner is pro driver with CDL-A, this truck has the original U-joints and brake pads and it gets worked.

Owner reported after very long overdue coolant flush yesterday that the truck runs smoother. I thought, well, anything is possible, I don't know why, but I certainly know where to ask. Thank you all for your responses!

#4725678 - 04/13/18 11:14 AM Re: Is This Possible? [Re: CCI]
gathermewool Offline

Registered: 01/09/09
Posts: 6064
What did the effluent look like? Lots of crud?

Might have been localized hot spots, not near enough to the knock sensor to retard timing?

Might just be a coincidence, too

#4725712 - 04/13/18 11:53 AM Re: Is This Possible? [Re: CCI]
SirTanon Online   content

Registered: 06/23/14
Posts: 2253
Loc: Phoenix, Arizona - USA
As a rule, it won't necessarily make it run smoother..

.. but it will very likely end up making it last longer.

As others have said, though, if the coolant was in REALLY bad shape, crudded up, etc.. and causing hot spots, or making the thermostat stick open and causing the engine to run colder than it should, then yeah.. a coolant flush and refill could help it run better.
2010 Ford Fusion SE - 2.5 liter/6F35 Trans - 258,000mi
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