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Replacing Head gaskets on Ford 3.8l engine

11-02-2004, 01:56 PM
Hopefully this isn't too long...

This is not an all-inclusive guide to doing a head-gasket replacement job. I assume the reader has at least one if not more auto maintenance manuals for their vehicle and some mechanical ability. I now have three (for reasons noted below). This is just a summation of my own personal adventure in auto maintenance with lessons learned. I spent a lot of time researching related material on-line, and a lot of the stuff written here is an attempt to help others out who may have similar problems.

My 97 Ford Windstar's 3.8 liter V6 engine had been gradually losing coolant for some time, but everything ran fine, so I kept replenishing the overflow reservoir and let it be.

Then at around 128,000 miles the engine began to misbehave. It would misfire whenever the temperature outside went into the 90's and the engine got hot. When my wife took the van to the dealership, they told her that #2 spark plug was cracked and they would have to extract it. They wanted $401 to do this. When I called the mechanic later that day, the price dropped about $40 but I was not about to pay that much money to have the spark plugs changed. "Extract," indeed.

So, a trip to the Auto Zone and $28 later, I pulled the spark plugs and replaced them with slightly more expensive, but hopefully better working, double platinum plugs. The car started up and was more powerful the next morning, but the same thing happened later in the afternoon. I had closely examined the plugs, with special attention to #2. There was no fouling on any of the plugs, none were damaged nor cracked. They showed normal wear and were ready to be changed, anyway. I decided to change out the plug wires, $37, in case one of them was getting a little weird in the heat... no go.

I broke out the Chilton's manual and began troubleshooting. I checked the resistance values on the ignition control block: the primary fell within specs, but the secondaries were about 2K ohms too high. There are three coils in the 3.8, with two spark plugs in series with each other and the ground between them. When the Powertrain Control Module sends a ignition pulse to the coil, the plug on the positive side of the pulse in the secondary circuit would get the spark; on the next pulse, the polarity would be reversed, so the other plug would have the positive side.

So logic would dictate that if one cylinder were misfiring (I gathered this from my conversation with the Ford mechanic), the values of one of the coils would be different from the other two if it were causing the misfire. The values were the same. As a professional electronics mechanic, I knew that the publication wasn't always right, and I wasn't going to bet $70 that the coil was causing my problem. As it turned out, when I found and purchased a Hayne's manual for the van ($24 with a gasket scraper and cleaner), the values were within spec... Chilton's was low-balling the measurements.

I did a little research online and found that many owners of the 3.8 had problems with the EGR valve and all but one or two of the ports being clogged, the excess gas going into the open port(s) would cause misfires. I went and bought a $26 vacuum hand pump (with brake bleed capability) and began testing the vacuum devices. I also bought a generic OBD II reader for $45 at eBay so I could pull the codes off myself and clear the faults after fixing it. I found a faulty Vapor Management Valve (also known as a Canister Purge Control Solenoid), $53 online at

I had two codes: P0302, misfire in cylinder two, and P0171, fuel pressure low in bank #1. Well, I already knew about the misfire, but the bank 1 fuel pressure indication was new to me. That sounded like a problem with the injectors... perhaps one was sticking open and causing a misfire.

My online research also netted me another tidbit about the 3.8-- Ford had a recall out for various 3.8 liter engines for bad head gaskets. While my engine fell into the category, I had already gone outside the timeframe/milage limitation... and my head gasket hadn't obviously blown. But.

If I had a minor leak in one of the head gaskets, that would be why I was losing water. I had checked the hoses numerous times, and the leak was so minor that I could never find a drip to trace. I hoped that if I pulled the intake manifolds, that I would find the cause of my misfire (I could clean out the EGR ports and check the injectors at the same time) and maybe I would find the coolant leak as well.

A guy in the How What Why forum online suggested that I do a pressure check on the cooling system to look for a minor head gasket leak... just checking cylinder compression would yield results only for a major blow-out because of the margin of error. I rented a pressure rig from the Auto Zone at the same time I bought my intake gasket set.

First thing I found was the radiator cap letting go at a lower pressure than it was supposed to... $6 for a new one. Then I pressurized the cooling system to 18psi (the system is supposed to run at 16psi which is when the radiator cap is supposed to open and purge excess coolant into the overflow reservoir. It was releasing at around 12psi) and let it sit for a few minutes. After five minutes, I could see that the needle had moved. At ten minutes, the pressure had dropped to around four psi-- I had a slow leak.

The next test required me to turn on the engine and monitor the pressure. In less than a minute the pressure in the cooling system had shot up close to thirty psi, which is the limit of the equipment I was using. The needle wasn't shaking, so there didn't seem to be any blow-back into the coolant, but the manual said that if the pressure shot up like that, there was a blown head gasket. I shut off the engine, leaving the system pressurized at around 26psi and lifted the front of the van onto stands.

I examined the hoses and ports into the block. I checked the freeze plugs and looked closely at the water pump, but no moisture. Finally, I crawled all the way under the vehicle and eyeballed the freezeplugs on the backside of the block and looked up at the head. The block below the head was wet. The extra pressure allowed enough water through to wet nearly the entire back side of the block, but even then there wasn't enough to cause a drip. By the time I got back out, the pressure in the cooling system had dropped to 5psi.

Auto Zone was kind enough to refund the $45 I paid for the intake manifold kit, but they didn't have a head set... I would have to order it. The prices online varied, but I finally found a Felpro kit for $139. With new head bolts, shipping, handling and taxes, I ended up spending $189, again at

At the time, I couldn't find anything that told me what, exactly, is contained in a head gasket kit, so I didn't know what else I might have to buy to do the head job. I had to decide whether I should begin tearing the engine down then or wait until I had the kit in hand so I wouldn't end up waiting forever without a van because the order was incorrect or incomplete.

I started the teardown before the kit arrived. I pulled the lower intake the first night. Ford has a thing for 8mm bolt heads on this engine, you really need a 8mm box wrench to get at the IMRC vacuum motors. They need to come off or at least be loosened enough to get them out of the way of the two intake bolts on that side. Don't forget to drain the coolant before pulling that lower intake off. You will end up with a small amount of coolant falling into the block as it is. You will want to change the oil before starting the engine.

It would also be a good idea to clean the engine before you start, too much debris fell into the block that I had to clean out. Pull the accessories off, as well. They'll make getting to those IMRC vacuum motors and the coolant return line on the left side a whole lot easier.

You definitely want to use a chunk of cardboard or something to organize those intake manifold bolts, because they come in a couple different sizes. It was dark by the time I finished this phase. Up next, those pesky accessories like the alternator and such so I could get to the heads. The AC compressor is a pain in the butt because the bolts go through the front to attach it to the block. Both the Haynes and the Ford manuals say to pull the compressor and power-steering pump and push them aside without draining and disconnecting the fittings. There is a bracket attached to the rear head that holds the power steering hydraulic lines as they head aft. Be sure to unscrew that clamp or you will break it when you shift the pump. The power steering pump won't go anywhere until the ac compressor is loose, so the recommended pull sequence for accessories is as follows:

1. Alternator
2. AC Compressor
3. Power steering line clamp
4. Power steering pump

Also, you'll need a puller for the power steering pulley... one of the bolts holding it to the head is directly behind the pulley and you will never get it out of you don't yank that thing off.

You need to get the accessories off before trying to get the front head off. The power steering pump and AC lines are right in the way of the last two bolts of the exhaust manifold.

Speaking of exhaust manifolds, WD-40 works wonders on those coupler nuts-- spray and let it soak in for a good half-hour or so.

There is a ground wire that runs from the rear head to the chassis. Disconnect it from the frame from underneath in the right wheel well. Also, you will need a second hand and lots of patience pulling that rear head off-- There is a bolt on the tension pulley that would not come all the way out (where the other end of that ground strap is) and so I left the pulley assembly on the head when I removed it. That makes it way awkward trying to extricate without scratching those machined surfaces.

I cleaned and inspected the heads. Mine are in good shape, after getting all the deposits off, but the exhaust valves had pitting on the mating surface. This is a normal occurrence, but it is a good reason to send the head in for machining.

Don't forget to lap your valves before reassembling the head. I used a lapping compound I got at Autozone, thinned it slightly with water first, then gradually thinned it out, removing some of the grit from the valve and dripping a little water into the paste left on the seat. You are going to work your hands off spinning valves, so take breaks often, or convince someone else to help you out. I put a final polish on my valves by lapping them with WD-40 vice lapping compound... they're nearly as shiny as the factory job.

As I mentioned before, this engine is all metric. If you can throw out a few bucks, get a metric tap and die set to clean out the threads on everything before reassembly... this is especially helpful for those areas that were secured using threadlock. I started with a little tap set from Autozone, but the cheesy handle I was expected to use was a typical compression-type and it slipped too much as soon as I got some resistance. I ended up using a crescent wrench to finish the job and returned the set to Autozone. I bought a full metric tap and die set at Harbor Freight on sale for $13... with a real t-handle, the second head went very smoothly. Use compressed air or the little red tube with your can of WD-40 to flush all the cuttings out of those blind holes; there's not a lot of room in there when the bolt goes in, and the extra metal compressed in the bottom can cause false torque readings.

Valve spring compressors are a pain in the ass. Neither of the two I used were narrow enough to engage the top of the spring... I had to "adjust" them with a hammer a tad to ensure I would actually be able to compress the damn thing. The second one had different-length arms, ostensibly to give a more linear compression on the spring. Riiight. The arms were also too long, and it was a bear trying to compress the springs enough to remove or install the keepers (I kept running out of screw). That set went back to the store when I was done with the second head.

Note to self: the extra fifty cents is well worth the price for the stainless steel wire brushes for the Dremel tool... the cheap ones don't stand up to any use, and yet I have worked three valves over with a stainless brush and haven't made a dent to it, figuratively speaking.

There was a lot of sludge in the intake ports of the heads... gotta love that EGR. I used a toothbrush and WD-40 (I got a gallon can), which made short work of it... nice and shiny afterward. Of course, bright and shiny is never going to happen of the exhaust side, so don't put too much effort into it, the stuff is baked right into the metal. Use bottle brushes on all the holes-- spark plug port, fuel injector port, lifter holes, bolt holes.

After the heads were assembled (yay!) and awaiting installation, I started cleaning the pushrods. I noticed that two of them had wear patterns on them. Normally, the pushrods will turn a little as they work, so the entire tip of the rod will be polished. When they stick, then the wear becomes uneven, the tip is ovalled and you can tell how the rod was oriented in the assembly. So, two pushrods went on order. I also replaced all the rockers because of excessive wear in the fulcrum area... the fulcrums have a little groove running around the base to get oil into the interface with the rocker arm. If the rocker wears to the point that you have a ridge growing into that lubricating groove, you want to get new rockers.

Next was the lifters. The Ford 3.8 uses hydraulic lifters, so every time the cam lobe raises the lifter, it pumps oil up the push rod to feed the rocker arms and valve train. Only one of my lifters was working properly, the rest were gummed up. Cleaned them out with a mixture of WD-40 and engine oil, but in the process managed to lose two spring clips, so I had to order two lifters as well. At least I knew why my rocker arms were so worn...

And that's the reason, my friends, why you really need to change your oil on a periodic basis. So, $149 for 12 rocker arms, two pushrods, and two lifters.

Well. Got everything put back together, finally, and tried her out. Engine started... but ran very rough. Part of it was the PCM relearning the engine, but there was still something wrong. The engine was running way too rich and was backfiring when I drove it down the road. It would threaten to stall when I put any load on it, such as placing the engine into Drive. If I backed it out of the driveway, stopped, and immediately threw it into Drive, it did stall.

It looked like I had a vacuum leak. Before I had disassembled the machine, I was pulling 21, almost 22 inches of mercury for vacuum. Now it was barely 18. Since I had checked all the vacuum components and the tubing, my only conclusion was that there is a leak in the intake manifold, so I had to pull it off and redo it. The blue gunk I had used to seal the gasket didn't harden... it should have been a form of RTV, so it should have hardened to a rubbery consistency, but it was still goopy after a week, and the air was probably blowing in right past the stuff. What the friendly folks at Autozone had given me was flange sealant, not RTV; it wasn't supposed to harden. So, on advice from my pet mechanics at work, I got some gray high-temp RTV for the installation.

Still hadn't isolated the vacuum leak. I then found out that there are two different sizes of lower intake manifold gasket available for the 95-98 3.8 liter engine-- 3mm and 4mm.

Now a millimeter is a fairly small amount, and the difference would seem to be negligible. But. It may just be the difference in having a sealed block or not for vacuum. The Felpro kit I got had 4mm intake gaskets, but the one used for the original equipment 97 3.8 was 3mm, apparently. Dragging this information out of Ford and/or the internet was a real pain in the ass... if you put a new intake on your engine, I guess you will need to go with the 4mm gasket.

So, another $50 or something for a new lower intake gasket, plus I threw down $12 for IMRC bushings (or retainers, depending on who you talk to) at the dealership. I couldn't find an alternate source for these little things online. Shop around your area-- one Ford dealer charged me $6 a piece for these little bushings the size of a pencil eraser, the other wanted $8.15. The dealerships are literally a 25 mile drive away from each other.

I also managed to get one code out of the car, P0174 Bank 2 Lean. Remember that part of my original problem involved code 0171 bank 1 lean. I had moved the #2 fuel injector to cylinder 4, and this sounded like an injector that sticks occasionally. One fuel injector on order-- $27.

The rainy season started with a sudden shower. Of course I, not knowing that there was rain in the forecast, took no precautions and left an open block to the aforementioned elements.

I was not a happy camper. The third time I'd had the lower intake manifold off and still no indication of where the vacuum leak was or had been. I'd even gone as far this time as to polish the gasket surfaces on the block and intake with the dremel.

I had some damage control to do, since I had to pull the valve train out again to take care of my water intrusion problem. I needed to clean all those components up (I left them soaking in either motor oil or WD-40 for a day) and put them back in first, then the Intake would go back on.

Word of advice to the potential mechanic-- torque the rocker arms into place before installing the intake. While it can be done the other way, it is much better on the nerves to be able to see that you seated the push rods correctly and visually verify that the lifters are on the cam circles before performing that first torquing step.

I flushed the heads and block with fresh motor oil and drained the pan. In total I poured three quarts through the engine before putting everything back together.

I took this reassembly slow and methodical, trying hard as hell to ensure everything went where it belonged and I got a solid seal. If it didn't work after this, I was going to throw in the towel and take it to a mechanic.

I started the engine up, and it sounded better, but it was still running rough and rich.

After fighting with the damn machine for a week and a half, moving fuel injectors around and ringing out wiring harnesses, I finally found the crossed 5&6 plug wires... the engine ran 100% better.

I feel really stupid for crossing those wires... I must have checked that block five times looking for just that problem, but not actually reading the label. Good thing I caught it, I was about to throw $178 or so on a new computer (or roughly the same amount at a garage).

So, lessons learned:

1. Wash the engine before starting. I did too much cleanup from outside dirt and debris falling into the engine.

2. Pull the accessories off first. For the front head, the alternator, power steering pump, and A/C compressor must be pulled (the pump and compressor can be pushed to the side). The compressor being removed helps free the power steering lines to the pump... why drain the pump if you don't have to?

3. The Power Steering pump pulley must be removed before the pump can be pulled off the engine... one mounting bolt is right behind the pulley. I got a removal/installing tool at Autozone for $36.

4. The Ford 3.8 liter engine is all metric (except for the spark plugs). You'll need 7, 8, 10, 13, 15mm sockets and combination wrenches. The 8 and 10mm, in particular, are popular sizes. You'll also want a long extension (8") to get the exhaust manifold flange in the back. YOu have to jack the van up to do this... give yourself some room and raise the van until the wheels no longer touch the deck. Be safe and use jackstands.

5. Invest in a quality pair of mechanic's gloves... they'll save you from the ubiquitous skinned knuckles. They also allow you to do some work on a hot engine. I used some all-purpose gloves I bought at Lowes (originally to use while pulling wire... no blisters, yay!) for around $25.

6. Those head bolts are a bear... use a breaker bar and be ready when it goes, 'cause you're going to be putting some back into it.

7. WD-40 is just the thing for freeing those exhaust manifold couplers... spray and let it soak for a bit. If things start feeling tight, back it up a little and spray again.

8. If you can do it, get more than one manual. I have the Chilton's and Haynes manuals... each hits details the other does not. Of course, if you're reading this, then you are smart enough to go looking on the web for additional info, too. Go to and subscribe for a month to get access to the vacuum/wiring diagrams, maintenance manual and power control and emissions manual.

9. What's in a Head Gasket kit? Well, the Fel-pro set I bought (HS-9250 PT-3), lists the following:

Head gasket Left hand
Head gasket Right hand
Water Outlet Valve cover (x2)
Throttle body
EGR Intake and Exhaust valve stem seals (x12)
Fuel injector O-ring (x6)
Valve cover grommets (x10)
Intake Manifold front seal
Intake Manifold rear seal
Intake Manifold Upper (x6)
Air Bypass Valve
Exhaust Manifold (x2)
Intake Manifold Left hand
Intake Manifold Right hand

10. Which kit do you need? For original equipment 1997 3.8 liter, you need the Felpro HS-9250 PT-1 head gasket kit with 3mm intake manifold gaskets. The PT-3 is used if you have a new intake manifold in place and you need the 4mm gaskets. Use High temperature sensor safe RTV sealant for those corners.

11. RTFM. Twice. Then have someone do a sanity check on your work... if the beloved spouse had been there, chances are high that she would have spotted the 5/6 plug wire snafu (wives are good for that).

12. Rather than use a fuel pressure rig (if you don't own one) to depressurize the injector rail, open up the panel in the back of the van, pull out that collision cut-off switch and shake it until the button pops out, then run the engine until it dies.

13. Close the power windows before you disconnect the battery.

14. Tools you'll need:

Metric socket set (6,8,9,10,13,15mm)
Open-end/box combination wrenches, metric (same sizes as socket set)
Slipjoint pliers (for the coolant hoses)
Torque wrench up to 100 ft/lb
Torque wrench up to 140 in/lb
Socket wrench extensions-- wobble extensions are nice for some areas, but you need solid extensions to torque with.
Fuel fitting compression-lock tool for Ford engines
Power steering pulley removal/installation tool
Gasket scraper
Metric tap and die set with cutting oil
Valve spring compressor
Valve lapping tool with lapping compound
Magnetic retriever thingy-- you'll be dropping stuff left and right and it's useful for pulling those lifters and valve retainers out.

15. Consumables you'll need (other than already mentioned):

Motor oil-- I use the recommended 5W30, you'll need a couple quarts to flush that coolant out and enough to change the oil a couple times.
Coolant-- same as above, safe for aluminum heads.
Engine assembly lube-- lube those moving parts until the oil can get back to them.
WD-40-- don't be home without it.
Cleaning solvent (I used a gallon-can of WD-40, but that's me)
Assorted brushes
Lots of rags-- I went through a five-gallon can full of them.
Masking Tape-- mark all those connections so you don't mix things up.
Gasket solvent

So... final cost-- $551 in parts (including an extra gasket set and not including common consumables like the oil and coolant which I already had on hand) and I have myself $144 worth of new tools. And three months.

11-02-2004, 06:44 PM
Excellent! Excellent! Excellent! Informative and witty... a good laugh at #13.

11-02-2004, 07:30 PM
Just a note, if you still have a misfire, it would be worth it, to check the injector cups on the fuel rail for crud. That is what caused our continued misfire after fixing our blown head gasket...well it took a total of 2 weeks to complete, as my wife was constantly naggin!! :)

11-02-2004, 11:01 PM
Just a note, if you still have a misfire, it would be worth it, to check the injector cups on the fuel rail for crud. That is what caused our continued misfire after fixing our blown head gasket...well it took a total of 2 weeks to complete, as my wife was constantly naggin!! :)

:smile: Nope, it works like a charm, wife actually complained that she has to be careful stepping on the gas, because it has power now.

Next up, my Saturn... squealing pulley somewhere :sly:

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