replaced heads on 93 4.0 aero, now have overpressure in cooling system.
no instructions in chilton or haynes. I followed torque sequence as instructed.

 

what are the symtoms? overheating? coolant blowout? hose swelling? coolant noise?

Ford 4L requires new head bolts, cannot reuse old...these are a one time torque to stretch condition bolt...no bolt sealant required

there is a left and right side head gasket, not interchangeable

is thermostat in correctly? longer pellet side in toward block

did thermostat get damaged while engine apart?

did stainless steel spiral spring get placed back in lower return hose to prevent collapse?

did you compare new head gaskets with old gaskets to make sure they were a coolant hole match?

did you pressure flush out block after replacing head gaskets, corrosion/mineral buildup around coolant holes breaks off during disassembly and can plug block chambers

blockage can also be in mating of intake manifold to heads since coolant flows from heads out thru intake manifold passages to thermostat and outflow hose to radiator

 

George! There is only one way to undestand, what is going on. First! Remove spark plugs. Remove radiator cap. Using compressed air check for leakages from cylinders to water.

There are many different problems, that may cause it! May be gasket is damaged, may be head is cracked. Difficult to understand!

This way is cheap but very effective!

About bolts sealant. I used RTV!

 

George:

Welcome to our FTE forum

 

Hi, if your coolant system is overpressured then you have a blown head gasket no question about it, as long as you dont have any cracks in the heads also these 4.0 engines are very prone to cracking heads especially if the engine has over heated in the past, you must have either put the gaskets on **** eyed or maybe the head is not torqued down correctly.

 

George:

Did you use new head bolts? If not, that's your problem right there. The head bolts for the 4.0L cannot be reused.

 

The head bolts should never be reused on any engine, but these guys are right, never on the 4.0L. Also, did you have the head checked for warpage or cracks?

 

I'm totally new at using this or any web site, so feel free to bawl me out if not doing it correctly.

My headbolt story, so others don't make same mistakes:
tossed heads and gaskets in a box, took to machine shop. bad move, should have kept the gaskets so I could compare them with new ones.
Shop hot tanked and magnifluxed heads, several seats were washed out, they rebuilt heads for about 260 bucks.
ordered gasket kit, 115 bucks, ouch, new bolts 30 bucks.
In gasket kit, no marking at all on one head gasket, other had the word topline on one side, thats it. No matter how I laid these gaskets on the heads, some passages were blocked by the gasket...maybe that should have been a clue
but the old gaskets had been tossed by the shop.
It appeared that the gaskets could only go on one way, so I proceeded without further checking things. another mistake.
There was some hard yellow color stuff on some of the old head bolts, some were clean, I paid no attention to this, should have. It must have been some kind of sealant. The manuals say just lightly oil the new head bolts except where special sealant is required, but they give no clue as to what and where to do so.
I only noticed that sentence after I finished the job., carefully following the chilton manual.
The symptoms are:
van runs very well, no overheat, but some bubbling in the coolant with the cap off, and the overflow tank fills, and a leak has developed in the radiator, where the plastic and aluminum meet along the bottom.
Something is amiss, as they say.
I am going to sulk for a few days while I decide whtat to do.
I appreciate the replies so far.

 

head gasket leak....intake manifold would not product bubbles in coolant, blown rad. tank seal and blowoff of coolant into overflow tank
don't run this engine....look for coolant in oil, creamy whitish appearance....Bearing and journal Death
no coolant in oil is a VERY GOOD thing

your head investment is worth saving....will require new head bolt set and new head gasket set...special sealant is optional or specified as Chilton says and not even listed in Ford service manual...use Permatex® High Temperature Thread Sealant if you can find it....

http://www.permatex.com/products/automotive/thread_compounds/a_thread_sealants/auto_Permatex_High_Temperature_Thread_Sealant.htm

only head bolts that need it are ones that are open at bottom into coolant passages....you can probe bolt holes with stiff wire or probe...be careful of threads
1. stuff cylinder holes with rags to prevent debris from lodging between pistons and walls.

2. completely scrap and clean block mating surface of any old gasket material or debris, do same on heads...use a sharp edge automotive type head gasket scraper....be careful to not deeply scratch cast iron surface
did shop check heads for flatness and/or did they resurface plane grind heads? will also need to check engine block deck head mounting surface for flatness, less than 0.003" in any 6" surface or less than 0.006 across length of deck...use high quality straight machine shop straight edge...I've never seen a Ford OHV V6 block warp in deck flatness except in severe overheating
do a final run over head and block deck with straight edge to check for any dirt or debris chunks just before setting on gasket and head

3. blow out head bolt holes with compressed air...i usually spray first with brake cleaner then compressed air especially when block has not been solvent tank dipped...wear eye protection

4. make a pattern drawing of holes that need sealant, ie, open into coolant chambers.

5. new head gaskets should have arrows which must point to front of engine for correct orientation.

6. torque sequence and steps are critical with torque to yield head bolts....Chilton's has correct procedure

i think the problem you will find is a chunk of debris; water passage mineral, carbon, grease, road dirt, old gasket particle prevented a strong seal on new gasket between one cylinder and water jacket hole
Cleanliness is next to godleyness when doing head gaskets especially in a rig such as an Aero which is so difficult to work in the engine compartment....almost impossible to prevent a particle getting between the head and gasket when putting head on engine still in engine compartment...even greasy finger prints on head/block deck or on head gasket can cause seal problems...

$150 gaskets and bolts, a little sweat equity and you will have a sweet running 4L Aero again and be cruisin down the highway shortly....

 

I'm not sure about 4.0 in aero, but it is possible to remove intake and heads if there is 3.0 in aero. It is difficult, but possible. May be to remove cyl.head you have to remove engine first.

I know, how to serve 4.0 on explorer only....

BTW, on old russian trucks with V8 engines, bubbles appeared in radiator, when water pump was going to go out. Do the pressure test before! The best way to make an adaptor to connect compressor is to use old spark plugs. Just broke ceramic part, remove everething out and using welding connect a metal pipe to it.

 

Pulled cylinder heads back off my 4.0
the first gasket kit I used was bought at the machine shop, a non ford product that was not marked as to top or front.
I bought some ford gaskets, properly marked top/front, just like in chilton manual, and sure enough just like 96_4wdr said, I had put the first set on incorrectly.
Even worse, bumbling amateur that I am, I rested the head on a scrap piece of wood that I laid across the block so I could change my grip on it before heaving it onto the block. When I took the old gasket off there was a sliver of wood about the size of a match head embedded in the gasket. Score another one for 96_4wdr.
Didnt find any coolant passages in any bolt holes but there was signs of sealant, so I used the recommended sealant on another set of new bolts. My thinking regarding exhaust leaks through the head bolts was way off.
I started this project because my engine with 140,000 miles had 85 psi in no. 1 cyl, zero psi in no.4 cyl., ran really ratty.
So now my 4 and a half cylinder engine is back to being a V6.
I love my aerostar except when I despise it.
So thanks for all your good responses.

 

Congrats on persevering ColdGeorge,

Most of us know that there is nothing more irritating then busting your butt, trying to get something right, only to be worse off than when you started after the first try.

I'm glad everything worked out in the end.

Dan