Fluid recommendations

[Jeff Romig]

Time to change fluids in my 05’ FGT. Looking for the latest recommendations for:
Brake / Clutch fluid (is there a fluid with different color so you know when you have it fully bled?)
Transaxle fluid (still recommending Motorcraft XT-75w90-QGT?)
Engine and Intercooler coolant (I’m planning on the Motorcraft VC-7B)
Ford manual says to use stop leak pellets in intercooler. Is this necessary?

 

[nota4re]

1. We use Motorcraft Brake fluid for the clutch/brakes unless car is used on the track - then we use Motul 600. The brake fluid is pretty clear and so easy to tell when the old (darker) fluid has been flushed through.
2. Yes. ONLY use the Motorcraft XT-75w90-QGT for the transaxle. 4 quarts. Remove and clean BOTH drain plugs - a screen on the left side, magnetic plug on the right.
3. VC7B is the correct stuff. Mix 50/50 with distilled water
4. No need for pellets.

Would recommend installing a Fumoto valve on the oil reservoir so that you are not having to remove/install drain plug with each change. Also adds a bit of convenience as well. (We have a kit with the valve, and two magnetic drain plugs for the pan drains if you are interested.)

Check power steering level. Check rear toe-link boots. Check SC fill level.

 

[Art138]

I have consistently used Castro’s SRF for brakes/clutch. Used it on my Viper ACR and Scuderia. Several members recommended it to me in 2011.

 

[2112]

I am lazy.

 

[Biginch Blake]

On break fluid the Motocraft DOT 5.1 is the best all around fluid out there. Boiling point 385 deg. F. The Castrol SRF does not preform any better and cost twice as much. Have switched my race cars over and have 2 years of great experience with it. Use for clutch fluid too. Also Castrol is had on seals.

 

[Art138]

I have been using the Castrol SRF for 10 years without seal issues.

 

[PeteK]

Let me remind everyone that DoT 5.1 synthetic brake fluid and DoT 5 Silicone brake fluid are completely different and NOT COMPATIBLE! Don’t get confused and mix them up. They will separate out like oil and water, and lead to expensive corrosion problems in your brake system.

While you should use the 5.1 specification, since that’s the best available now, you can also use DoT 4 (Ford’s original recommendation) or even DoT3 in a pinch—say, if you’re stuck in Timbuktu on a holiday weekend and for some strange reason you need brake fluid, and that’s all the 1960’s-era Western Auto store has on the shelf. They are all glycol-based fluids and will mix.

The lower specifications simply have lower wet boiling points (the temperature at which the brake fluid will boil after it has absorbed moisture). If you aren’t doing track days where the brakes get really hot, you will never notice the difference. The brakes on our GTs are sized for 200 MPH full stops, so in street driving you almost certainly will never approach the limits of the brakes.

And let me repeat my public service announcement from a few months ago: change your brake fluid regularly (including clutch). If you’re in a humid environment, like the east and south, every two years. If you live in a dry environment, you can double that. If it gets darker than your pee, change it.

 

[Biginch Blake]

Pete K, he asked about changing fluids. You are correct you should not mix fluids. If you have to add break fluid always try to use the same brand, if you have to add regularly you have other problems.

Several of us track junkies had slave cylinder failure and (unscientifically) traced it to the Castrol, changed to the Motocrft 5.1 and no more failures for 2 years. This is under extreme conditions.

Always take time to make sure you get all the air out of the cooling, break and clutch system.

 

[Indy GT]

1. We use Motorcraft Brake fluid for the clutch/brakes unless car is used on the track - then we use Motul 600. The brake fluid is pretty clear and so easy to tell when the old (darker) fluid has been flushed through.
2. Yes. ONLY use the Motorcraft XT-75w90-QGT for the transaxle. 4 quarts. Remove and clean BOTH drain plugs - a screen on the left side, magnetic plug on the right.
3. VC7B is the correct stuff. Mix 50/50 with distilled water
4. No need for pellets.

Would recommend installing a Fumoto valve on the oil reservoir so that you are not having to remove/install drain plug with each change. Also adds a bit of convenience as well. (We have a kit with the valve, and two magnetic drain plugs for the pan drains if you are interested.)

Check power steering level. Check rear toe-link boots. Check SC fill level.

I agree with the guidance Kendall recommends above. Stick with Motorcraft fluids as they work just fine and were used during the development and certification of the car to much higher usage/temperature levels than the average GT owner will ever achieve. The Fumoto oil drain valve (F107N 12MM-1.75) screwed into the bottom of the oil tank reservoir really makes the oil change much easier and cleaner. Good option to install.

 

[HighHP]

So here is a question I think of each time I read about changing the clutch fluid to a different type. If you flush with a different non-compatible fluid, the fluid from the rear bleed down into the clutch slave does not get replaced. Also, if you are having high temp problems with DOT 3 or better (or have moisture problems) and change the fluid, still leaves the old crap downstream from bleed???
Any thoughts or fixes for this?

 

[PeteK]

Blake, yes I understand that Jeff is planning to change his fluid. However, I’ve seen several people make the mistake that DoT 5 and DoT 5.1 were basically the same thing, then had to completely drain and blow out their brake systems to get the DoT 5 stuff out. Or vice versa. I guess they’ve been conditioned by computers and phones to thinking that 5.1 is a more recent version of software, so should work with version 5.0. Thus, my warning to anyone unaware.

 

[PeteK]

So here is a question I think of each time I read about changing the clutch fluid to a different type. If you flush with a different non-compatible fluid, the fluid from the rear bleed down into the clutch slave does not get replaced. Also, if you are having high temp problems with DOT 3 or better (or have moisture problems) and change the fluid, still leaves the old crap downstream from bleed???
Any thoughts or fixes for this?

Ed, there are only two types of brake fluid: Glycol-based and silicone-based. They are not compatible as discussed above. The silicone stuff will float on top of the glycol stuff, so eventually you can bleed it out if you want to replace DoT5 with DoT5.1. Although, trust me, it takes a lot of bleeding sessions to get it all out! BTDT.

The DoT3, 4, and 5.1 are all glycol-based and are compatible. As noted above, you want to stick with DoT5.1, and if you use the Motorcraft brand, you will be assured it meets Ford specs.

The shop manual gives a procedure for bleeding the clutch fluid that gets the old fluid out of the slave cylinder, downstream from the bleeding valve. Read it and you will see how it works. I’ve done it twice.

 

[Indy GT]

Good advice Pete. Do not mix the DOT5 (Silicon base) and DOT5.1 (Glycol base) fluids.

For those technically inclined and curious, all the North America brake fluid requirements are found in DOT Federal Motor Carrier Safety Administration, Standard No. 116; Motor vehicle brake fluids. A plethora of information to satisfy even the most curious individual.......