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Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

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Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

This post was updated on .

Evening Gentlemen,

SO here is the latest. Still trying to track down this leak:

Engine is dry around the intake, block is dry on the sides and the front. But I cannot figure out what could be causing this leak. Any thoughts?

Here is a 16 second clip of the leak with the engine running:
https://youtu.be/f2GmA2lLhro

Jamie Helmick
'85 Bronco 351W HO, C6, 4X4, Full rebuild @ 51k original miles (fire), Edelbrock air gap intake & 600 cfm carb. w/elec. choke. 4" RC lift w/35's. Check the Projects Page if you're interested.

Rembrant

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Ferdinand wrote

Engine is dry around the intake, block is sry on the sides and the front. But I cannot figure out what could be causing this leak. Any thoughts?

Well, I don't think there's anywhere for coolant to leak from the back of the engine block, unless it is cracked. So...for a moment, leave that as a worse case scenario.

Likely cause imho would be a leak between the intake manifold and cylinder head(s). Most common SBF coolant leaking area imho.

If not from there, then I'd be checking the head gasket(s). Gary or one of the other guys on here can confirm...but I know on the 302, the later versions of these blocks (1984-ish and up) the head bolts thread directly into the coolant jacket of the block, and special thread sealant must be used during assembly. The earlier blocks had blind holes for the head bolts, so it was a non-issue previously. However, I'm not sure if this is an issue that is specific to the 302/5.0 or not. It may be the exact same thing with the 351 as well.

If not one of the head bolt threaded holes, then maybe a head gasket.

If not a head gasket, then maybe one of the press in plugs on the back of either cylinder head. (This seems the most unlikely to me, but worth checking anyway).

If it was me leaning over your engine bay, this is what I'd do. Make sure the area at the back of the block above the bell housing is spotlessly clean and dry. Spray brake cleaner around if need be and let dry. Get some dry powder of some kind (like talc maybe?) and sprinkle a little bit around back there. Get a coolant system pressure tester (rent, borrow, or purchase?) and test. Look for wet spots.

If everything above the bell housing checks out as dry and leak free, then I don't think you have much choice after that point but to pull the transmission or pull the engine.

I'm certainly no expert, so one of the other guys on here might have better ideas on next steps.

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

I agree with Rembrant. The idea of using a pump up tester is an excellent one as it will work quickly and will keep things cool and easier to work on.

But you might consider adding a dye to the coolant. Here's one at Amazon: https://www.amazon.com/Interdynamics-Certified-Engine-Cooling-Systems/dp/B002M4E0VC. They allow you to find a leak using UV light, which sometimes is the easiest and fastest way to find a leak.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Ferdinand

Excellent thoughts gentlemen. Thanks for brainstorming this with me. I'm no "mechanic" by any means, but when I rebuilt my '82 F150 I didn't have any of these problems! 🙃 I will keep you posted.

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Gary Lewis

Side note, I must not be holding my tongue right... I have tried about every version of Width = "100%" I can think of and I cannot get it to work. It it maybe a MAC thing?

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

Don't put the spaces in. It should be: width="100%"

Gary, AKA "Gary fellow": Profile

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

This post was updated on .

In reply to this post by Ferdinand

Well last night's investigation left me with what I feared the most...

Here is a 20 second clip of the motor running with the leak active at the lower bell housing as in previous posts, but no leaking at the freeze plugs in the rear of the heads or the rear of the intake.

-Sorry for the crazy angle

You will see a little bit of dried coolant in the valley of the intake. That was a small weep from a plug on the top front of the intake just behind the thermostat housing that I have since tightened.

I did most of the leg work last night. So, hopefully with 3 more bolts to remove, the transmission and transfer case will be down and out tonight.

Anyone have any advice on the things I should investigate/replace on the C6 auto while I have it out?

The NP Transfer Case is also leaking a tiny bit at the case halves and I thought about trying to fix that but I am not sure if that is opening up a can of worms or not.

Thoughts?

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Gary Lewis

Thanks Gary, I will keep picking away at it!

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Ferdinand

Here are a few progress pics of the night I finally set the motor.

Man was I glad not to be tripping over that thing anymore!! (My space is limited, but I am thankful for the garage! My '82 F150 rebuild was outside in the winter, laying in the snow!)

Gary, I finally figured out the "100%" edit. Thanks!!

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

Truck is looking good!

I watched the video and didn't see anything that was suspicious. Did I miss something?

On the C6, if it is working well I'd leave most things alone. However, if you haven't changed the fluid lately I'd drain it, which is likely to cause a BIG mess, pull the pan, and replace the filter. Then, while you have the pan off, add a drain plug to it so you can change the fluid next time w/o causing such a mess.

On the t-case, I've not rebuilt one of them. But the issue may well not be with the t-case. Instead, it may be with the seal between the t-case and the tranny. There's lots of fluid there, coming from the tranny, and unless that seal is good you'll have a leak. The factory used a gasket, and I've used a gasket/RTV combo and I've gone back with just RTV. Either work.

Gary, AKA "Gary fellow": Profile

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Ferdinand

So pulling the trans and t-case went fairly well this evening. Most of the work was done last night. Headed back out in a bit to keep looking for the leak.

And may I say a cheap craftsman motorcycle lift makes a pretty handy transmission jack!

The "good" news is that I don't see anything wet inside on the back of the block. I can't see any cracks, and now that I have a REALLY good look at the intake, I can without a doubt confirm no leaks there...

However, I am completely S T U M P E D on where this coolant is coming from but I will certainly keep you posted.

Gary, thanks for the suggestions. I had actually pulled the pan, installed a new filter stripped and painted the pan and gave it a fresh drink with all new fluids before I fired him up for the first time. SO, taking the pan back off and losing all that fluid was NO FUN at all.

I like the suggestion of putting a drain plug in. I didn't even think that was an option, but you can bet I am putting one in this time!

Here are a few pics of tonight's progress:

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

Yes, that motorcycle lift sure looks like it worked nicely.

I think now is the time to get the cooling system tester from the parts store and pump up the pressure. Most stores "rent" them, meaning you pay as if you are going to buy it and then get your money back when you return it. Anyway, hopefully the leak will manifest itself w/o heat.

But, if you still can't see the source the next step would be the UV dye. However, since that probably won't mix with the coolant w/o the engine running you'll have to reinstall the tranny for that step.

Gary, AKA "Gary fellow": Profile

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Well I pressure tested the coolant system tonight...

Tried 10psi - nothing, 12psi - nothing, 14, 16, 18, 20psi developed a few small leaks around a few hose fittings but I didn't want to go any higher and risk damaging my new radiator since the stock coolant operating pressure is rather low.

So, at this point, I am guessing the leak doesn't propagate until under pressure and heat.

But as you mentioned Gary, to test that theory I have to reinstall the transmission to be able to run the engine. I plan to clean the case up and give it a quick coat of paint and give it a try.

Sounds simple enough, but I am guessing that will take me more than a week to accomplish.

Gary, you've used the expression of these trucks being like onions... man is that an excellent metaphor!
😣

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

Bummer! I was afraid of that. But, I agree that you don't want to go any higher in pressure as you'll stand a chance of damaging either the radiator or heater core.

But, think how clean and pretty it is going to look with the tranny (and t-case?) cleaned and painted!

Yes, it is an apt metaphor. If it isn't one thing it is another. And the question becomes how far you want to peel things. At some point in time you'll say "It is good enough", but it is obviously not yet that time. So, keep on keeping on.

Gary, AKA "Gary fellow": Profile

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

amen brother!

Tallyho

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

I admire your ambition! You look to be doing a great job with a worthy bronco. Maybe I missed it but did you ever determine why the engine caught fire?

Tallyho
1984 f250 4x4 460 4 spd
Raymond maine

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Evening Tallyho,

My best guess based on the charred remains under the hood would be either the stock air cleaner rubbed a hole in the fuel line or that it back fired through the carb. The guy did just do a new carb and wires and I wonder if something got mixed up in the process. It ran really well though on the two test drives though. I drove about 2 hours to go get it. And I made it about 1/2 way home... What a fiasco. 🙃

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Ferdinand

I did get the transmission and t case apart and am working on getting them stripped down.

Sure wish I could get that tranny up in the blasting cabinet! 🤣

Gary Lewis

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

Administrator

I've been known to tape everything off and use my roll-around blast cabinet outside on a transmission. But getting one in my blast cabinet wouldn't be easy. Too heavy.

Without a roll-around I'd use brake cleaner and brushes. I put a slip yoke in the output to seal it and something else on the input. Plus sealed the vent and all other openings.

Gary, AKA "Gary fellow": Profile

Ferdinand

Re: Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

In reply to this post by Ferdinand

Also, after leaving the pressure tester on the coolant system for about an hour, a very small leak started at the rear passenger side intake location. It is very small.

See annotated pic:

So, the question I am trying to sort through is: while running (see videos posted previously) this location did not appear to be leaking from any angle. All the while having an active leak some where that showed itself at the rear main crank seal. (see coolant leak video).

This is THE ONLY leak that has shown up (minus the hose connections when pumped up to 20 psi) so I am still "evaluating evidence". 🤓

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