Repeat intake/head gasket failure

borjawil · Nov 15, 2017

94 4.0L 219k

Ive replaced my intake gasket and head gasket twice now and once again I'm burning coolant. my surfaces are clean, the second time around I used an OEM ford intake gasket. Im using new head bolts. Im torquing them in the correct sequences and torquing the intake to 15-18ftlbs. Im using black RTV around the coolant passages and at the corners front and back where the head and block meet.

Ideas? at about $200 a head gasket change I could of bought a whole truck with a good engine by now.

adsm08 · Nov 15, 2017

Well the question you have to ask now is, what's warped?

borjawil · Nov 15, 2017

Well I was thinking that as well. Unless my intake gasket is failing or air in the coolant system is causing the gasket to blow.

1st time it looked like #5 cyl blew. 2nd time glove test said #5. this time glove test says #6 cyl. 2nd time glove bounced around, this time just filled with air slowly.

If something is warped how do I go about checking? I know where to go for my head - but I believe my intake is blowing, causing my cylinder to overheat and blow the head gasket.

adsm08 · Nov 15, 2017

Checking an in take isn't too different from checking a head for warp. Just a smaller surface area.

borjawil · Nov 15, 2017

Ok, can I just use a straight edge or is that not good enough? Any write ups on doing this?

RonD · Nov 15, 2017

How long between problems coming back?

I had a torque wrench for years and never had an issue with it, then on my THIRD 4.0l head gasket, I tested it.
It was about 25ft/lb low at 60ft/lb
New head gaskets lasted about 9 months, then failed, heads were cleaned, tested and surfaced each time, new head bolts each time
New torque wrench and now well over a year this time.

4.0l uses aluminum intake bolted to cast iron head
This means the aluminum will be eaten away by electrolysis at coolant passages as coolant gets older, so check the intakes corners for signs of that.

adsm08 · Nov 15, 2017

borjawil said:
Ok, can I just use a straight edge or is that not good enough? Any write ups on doing this?

A machinist straight edge is needed. Basically what I do is set the edge on the head, do both diagonals and straight across on the centerline of the long dimension, and across the short at each cylinder wall.

I don't even use feelers anymore. I use a flashlight, if I can see any light under the edge there is warp.

borjawil · Nov 15, 2017

Not long between them. Maybe a few hundred miles. Some short trips around town, but after the repairs I had 40-125 mile highway trips.

Im aware of the pitting that can occur. There is some I've attached a pic. How would I go about repairing this or is it not an issue? I coppercoted both sides of my head gasket before installing the 2nd time. Seems the coppercote stuck to the head and block but not the gasket. As you can see theres a good amount of pitting, though not super deep. JB weld it? Ive heard others doing so successfully, use more layers coppercote? use high temp RTV on head in location pitting is?

Also what is the proper torque sequence for the lower intake? Ive been taught to torque from the inside out. In the tech articles is says outside in. Ive also read the manual says outside in and it is incorrect? Can any one verify this?

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adsm08 · Nov 15, 2017

That's rough. I think it may just be time to invest in some new heads.

As for intake torque sequence, I have always done it inside out.

borjawil · Nov 15, 2017

Im going to go ahead and try to use them, need my truck for work and barely have enough to pay for the gaskets, bolts, oil, etc. Jb weld and a razor blade to apply it. Hopefully fill in the pitting. Ive read several posts on it. Coppercote my head gasket as. Ill torque from the inside out on my lower intake as well. Still apply RTV around the 4 coolant passages and at the 4 corners. Any particular RTV I should use? black, red? (high temp of course)

RonD · Nov 15, 2017

4.0l head has a weak spot in the casting, between valve seats
Image here: http://farm5.static.flickr.com/4104/4832374149_7a6dddcfef_b.jpg

Thats a big crack, most are much less obvious, have a look

Image here: https://www.ranger-forums.com/attachments/4-0l-ohv-sohc-v6-tech-33/201630d1501467118-check-out-my-head-oics-no-56k-img_1211.jpg

Has crack but also notice different in color with cylinder next to it

You are wasting money on head gaskets if a head is cracked.

I mention this because most take heads to machine shop for surfacing and also pressure test, which you are not doing

Failed intake gaskets rarely cause "white smoke" exhaust, burning coolant, gasket would have to fail on #1, 3, 4, or 6 and tops of one of those pistons would look steam cleaned, and generally you would get a hydro lock at next start up, because coolant would continue to flow into intake after engine was shut off, and then down an open intake valve to sit on a piston.
Next time you turned engine over it would lock up.

For bad intake gasket Vacuum leaks are more likely and coolant dripping on the outside of the engine

borjawil · Nov 16, 2017

Ill check for the crack between the valves but didn't notice anything when cleaning. When I removed the head my #5 was very clean on top and now #6 is very clean.

Ill be replacing the head bolts, but is there really any issue with reusing them? I understand tty bolts stretch...but on a specific bike engine I'm familiar with rebuilding, the cylinder studs should be replaced but a lot of people have been successful in reusing them. Basically torque them down. Let it sit over night or so, then retorque to make sure. Just wondering.

Im also thinking i may need to use a different torque wrench so ill be doing that as well.

borjawil · Nov 16, 2017

Well there you have it. Got a small crack between the valves on 6. ****.

What vehicles had/have the same 4.0l as mine? (94 4.0L OHV) Junk yard says 70 if I pull it so not bad at all.

EDIT: Answered my own question 90-94 are the same, 95 will bump my compression. Im assuming exploders 90-94 had the same heads/engine

RonD · Nov 16, 2017

Too bad about the head

Good read here on the 4.0l OHV: http://www.therangerstation.com/tech_library/40rebuild.shtml

And head changes over the years

borjawil · Nov 16, 2017

Awesome, thanks for the link! Time to go digging in the graveyard.

Any things to look out for when pulling them? As in I should walk away if I see "this".

Repeat intake/head gasket failure

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