Build Thread Mustang5L5's Build Thread -

95BlueStallion said:

Looks like you're low on a couple fluids.

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Eh. Those are just suggestions.

Mounted up one of the 18x9 +25 wheels. I might need to stick a small spacer on here. It’s pretty darn close to the tailpipe…and I want to keep the tailpipes. I think I can do a 1/4” spacer just to buy a little more room.


I should think about what tire size I want to put back here, but I’d like to get the 18x9 +35 wheels first and just test fit

I ordered up some Mustang center cap decals for these caps.

No spacer in that pic. Gonna have to get a tire on and see before adding one.

Farting around I took the car for another ride up the street and back to test cooling system. I did add some water wetter. Seems to be rock solid at 180-185 degrees now with ac on, but we haven’t had a heat wave yet. But more importantly it’s consistent and stable, which the other 192 stat wasn’t. Again…it might be just that particular thermostat sucked, and not the fact it was a 192.


In using my IR thermometer, I discovered two cylinders are running hotter than the others.

I get 225 at idle on all cylinders except for #3 and #8 on my warmup before I drove. Those two cylinders are right around 300 degrees. I measured top of the headers about 1” off the head.

I still have the 19# injectors in. They are old. I really need to get off my butt and wire in the MS and swap to the new 30s.

To test my theory, I may swap the injectors around and see if the problem moves. Or just wait…

In addition….

Not sure the hydroboost is working correctly. I’ve noted a few times on my drive that more leg effort is needed to stop than when I had vac brakes.

In doing some research and diagnosing, I think the pressure relief valve is opening too soon. When I put my foot on the pedal and give average brake effort, I head the chatter from the system.

@2000xp8 how much leg effort do you need if you pressed on the pedal at a stop before you hear that buzzing sound from the system?



I’m using a 2000 escort pump. Not sure if the relief valve in the pump is lower than the stock mustang pump would be? Need to do a little more research here.

Half tempted to toss a 93 cobra booster/MC back in the car, but that will be a total PITA.

I think the buzzing is the pressure relief on the 302 pump going off. In other words it’s just not supplying enough pressure to the hydroboost so my pedal effort is high as a result.

I’ll need to dig into this a bit and do some research. It’s fine for driving around town, but at higher speeds it’s actually a little worrisome.

I did the hydroboost in prep of a possible 4.6/coyote swap down the road. 50/50 if I’ll actually do it….


I wonder if the pressure relieve spring in this pump is a little on the weak side…

For example


Edit: reading the description. This valve will fit CII style pumps, which is what’s on the 302. Perhaps I should try it…

Ok...so went down the rabbit hole on my hydroboost issues.

Basically the symptom is pedal effort seems high. Hydroboost should have MUCH better pedal effort than with my old vacuum setup, but for some reason I'm not getting the level of assist. When I press the pedal with moderate effort, i can hear the P/S pump strain and see the rpms dip. If i rally stand on the pedal i can almost stall out the engine, but this is not a realistic braking scenario. It's strange because I think i should habve more braking power before getting to that point.

I almost suspect i have a huge restriction preventing full flow/pressure getting to the hydroboost

Our stock Fox pumps are known as the Ford C2 pump. I know it can work with hydroboost because 1999-2003 Ford F350's with the 7.3L come with the same type of C2 pump and hydroboost.

The SN95 hydroboost cars use a C3 style pump.

Specs on the C3 from what I can find are:
Flow: 9.8 Liters/min (2.6 gpm)
Engine at 1500RPM: Pressure 150 psi
Engine at 1500RPM: Min capacity 4.7 liters/min (1.25 gpm)
Relief Pressure: 1200-1380psi

For the C2 pump (stock 302 pump)
Flow: 5.3 Liters/min (1.4 gpm)
Relief Pressure : 1400-1530psi


I'm trying to see if the stock 7.3L pump has the exact same specs because that does run hydroboost and steering. Right off the bat, the 302 pump flow seems low, but not sure that's the case as i wouldn't think i'd be hearing the pump strain.

I'm using a Ford Escort pump. Perhaps there are some technical differences here I am not aware of and might require a slight change of hardware.

Yes, i found a number of threads from truck guys wanting to know how to upgrade that pump after sapping 35s or larger on and how it messes with the steering and brakes. I would think that would mean it could easily handle a fox mustang

As you can see, it looks like a standard fox pump but has two returns. One from the rack and one from the hydroboost. So i can certainly swap pumps around, i just need to retain the correct plastic body for my application.


Gotta do a little digging here. I'm wondering if the 1990 Ford escort pump isn't up to the task, BUT, it almost seems like i'm hitting a restriction somewhere. I'm browsing the Factory Five cobra forums and plenty of folks running hydro with stock Mustang 302 pumps.


Thinking out loud here....I need to make sure I connected the high pressure outlet to the right fitting on the hydroboost and don't have them swapped....

Pulled my #7 and #8 plugs. #7 and 5 others ran about 220 degrees while #8 was near 300.

Does look like that plug was running a tad hotter. I bet that injector isn’t as healthy.

7 on left, 8 on right





This guy came to habg out for a bit while I worked on the car. Just sat in the grass half asleep for 30 min before heading out

2000xp8 said:

Mabye i missed this part, but is there a reason you didn't just run a fox pump?

Click to expand...

Used the escort pump because the housing would let me use a remote reservoir. I assumed the mechanical part of the pump was the same. It still may be. I might just need to only swap the pressure relief valve.


But, i did some more digging last night and think i have a lead. I think the issue is the way I plumbed my low-pressure returns. I found a lot of posts on the classic bronco boards about this as they all seem to swap to hydroboost on their cars. The hydroboost needs no more than 3psi of pressure on the return line. Basically it needs to be unobstructed.

example of whati found

I tee'ed the two low pressure lines together with a single return to my reservoir. I think this might be the issue. The return from the power steering rack is high-flow and constant, but the return from the hydroboost is small. The recommendation is that if you TEE the returns, the power steering line goes on the "straight" portion of the tee so it has a straight shot into the reservoir, and the hydro goes on the 90* leg.

Guess how i plumbed it? Not that way. Basically my rack and hydro return are pointed at each other and have to make the 90* bend into the return leg. The thinking here is the rack return is pushing into the hydro return loop causing backpressure issues. Makes sense to me.

My symptoms line up to some of the symptoms guys who have restriction have experienced, so i buy this theory. The problem is I plumbed my lines with just enough lenght, so i can't just flip the tee and try it. Would need to make new lines and do a little rerouting.

Going to get a 6AN cap and unhook the hydro return and cap the tee. I'll just put the hydro return into an empty 5quart oil bucket and give it a shot. I'll know right away if this is the issue.

If it is, i can try flipping the tee, but I might need to add a second return to my reservoir or pick up one of those 7.3L PS pump housings with two returns (pic above a few posts) and go that route. That would probably be the most ideal situation but i would have to abandon my remote reservoir idea.


How do the SN95 cars do it? Ford tee'd it, and has the hydro return coming into the tee on the 90* leg. So looks like more evidence that I need to swap my tee around and might be able to get away with that vs adding a 2nd return to the bottle

Blue would be hydro return and red is PS return from the cooler

2000xp8 said:

As for the injectors, if you plan on using 24's or 30's, why not just buy a meter for now and swap them in?

Click to expand...

I should just go ahead and do that. I was kinda hoping i would get the megasquirt in soon, but the way my summer is going with the family trips we have planned, this might be a project for the fall.

Car still needs a tune either way. I definitely notice it's a bit on the rich side. Warm start tends to stumble a bit and sometimes require foot to the floor to get it to start. Points to it being overly rich.

At the same time, i don't want to buy a MAF and then drive the car 30 miles and pull it off when i go MS. I intend to set it up for Speed Density.

Let me sort this hydro issue out first. The brakes work, but not as well as they should from what i'm noticing. Given what i know now, i'm not going to drive it much until I get it perfect.

Yeah, a lot of the diagrams were worthless. This one is OK but the fittings are incorrect or don't work. I ended up going with something else.

But the return routine is where I messed up. The return line from the rack (#8) needs to flow straight through to #10 to the reservoir. #9 is the return from the hydroboost. I have #9 and #10 swapped so the two returns flow into each other. I'm crossing fingers this is the problem.