A few years ago I replaced the head gaskets on my 94. The step by step details are recorded here in another thread. It ran great afterward. The van became a spare and was seldom used.

When my daughters care broke it became her daily use van. I noticed it had a rough idle and I thought it was a vacuum leak but didn't bother with it.

When I got it back, I noticed that the rough idle was worse and started looking into it. It was not a loose vacuum hose as I expected.

Eventually I tried to do a compression test. I pulled the plugs on the right side but could only get the gauge in the front two plug holes. I read 160 and 160 if I remember correctly (it was several months ago).

On the left side I could only pull the front two plugs without breaking something. I read 60 and 90.

This is was still a spare at the time so I let it set as it was still drivable if I needed it and we continued to drive the 96.

Well my 96 (that was totaled in the Mother's Day tornado last year) was still being driven blew it's head gasket. Between the body damage (pictures in a separate thread) and the bad head gasket, I decided to cash in my insurance.

So now I need to figure out my 94 problem. I am guessing valves or valve seals. I just want to get other opinions before I buy gaskets and open the engine (again). What do you think?

 

If I remember right you should have all of the plugs out when you do a compression test. Squirting oil in the cylinder and reading if the compression goes up will tell you if it could be rings rather than valves causing low compression. Bad valve seals don't cause compression problems but they will cause you to burn oil. A good read on the plugs themselves might also give you a clue to what is wrong.

 

at 200k, i'd pull the engine and rebuilt it or go long block from a reputable rebuilder.
at that mileage, everything is worn out. rings pistons, crank and rod bearings, valve stems, camshaft probably lobe flat, worn out rocker arms, cam chain and gears.

too much money, work and blood investment to piecemeal it in chassis.

 

Might be a good time to put in a 4.3L stroker. Theres a company in canada, and I assume others, that increase the bore and stroke to get you 4.3L. That should have some nice performance to it. Not sure what that costs though.

 

The 4.0 is a former 2.8L engine that is already bored to the max. That minimal separation distance between cylinders makes is tough on head gasket lifespan. Boring it out even more will only enhance the probability of head gasket failure.

Its rather odd the right bank tests okay while both left bank are very low. Bad valve seats will produce a noticeable "puffing" sound in the exhaust. If the rings are badly worn, you should see evidence of oil fouling on those plugs. Your findings do not sound typical of the 4.0 engine. I would continue to investigate. Most problems turn out to be something rather simple in nature.

 

start by pulling the codes and please post here
what work has been done on engine in last year?
age and condition of plugs and ig. wires?
what is the history of oil changes? per Ford recommendation or numerous missed OCs?

after the minor bugs are chased down:
pull the alternator, unbolt the a/c compressor and set it off to the side at the end of it's hoses to make room
pull all plugs. disconnect control cable to coil pack
charge battery overnight on charger.

run compression test on all cyls. dry.

" " " after a couple squirts of motor oil in each cyl.

run cyl leakdown test on each cyl.

record and post results.

may be able to get another 100k on motor if not a major oil burner.

if it's the heads or valves leaking and you go into the engine, replace the timing chain/gears. they have to be sloppy loose after 200k
i'd pull and do the work out of chassis. to easy for DIYer to have foul ups in the tight cramped Aero engine compartment.

 

160 PSI is about right, below 100 is bad. The fact that both cylinders measure that low is pointing to head or block surface warped or cracked on pass side. Squirt a TBSP of engine oil into those cylinders & see if the reading gets to normal if so it's rings but I'd be thinking at this stage, your head or block is damaged. Does it start easily? Also does it seem to want to overheat, what about bubbles in the coolant? With bad rings you'd get smoke & oil consumption & black oil quickly.
It is also possible to do a leakdown test & get more conclusive results that way.

 

I replaced the head gaskets and installed new plugs and wires in Nov 03 at 184,100 miles. It now has 214265. That is 30165 since the rebuild. I didn't realize that it had been that long. Then again it's going on 6 years.

Since then I have changed the oil 8 times. The average mileage between changes is 3,770.

It has the old OBD-I system and the check engine light is not on but I haven't check for any codes lately. I can do that as I still have an old scanner.

At 199000 I rebuilt the front end with 4 ball joints, shocks, tie rod ends and control arm bushings but that is beside the point.

It starts easily and doesn't use oil. I have not noticed any coolant loss either. It has pretty good pick-up when you really press down on it. My son who was driving the 96 prior to the head gasket going said that this has more pickup than the 96. If you don't mind the vibration, it is usable. Is just shakes when it idles and there is a huffing noise in the exhaust.

I first checked for loose vacuum hoses. I replaced the TPS. I swapped in a new MAF and put the old one back as there was no difference. That is when I decided to try the compression test.

Doing the head gaskets pushed my limits on engine work. I don't think I'm up to actually pulling one. Don't have a lift or engine stand or garage.

I was hoping for something simple like pull the head on one side and rebuild it. I've got lots of spare parts now, however the engine parts are from a OBD-II (with bad head gasket). I can't sell it with engine problems and 214K on it. I guess I can get the compression gauge and try again.

 

if the head gaskets need to be replaced, don't forget that it is manditory to put in new head bolts. they are torque to yield one time use only. old reused bolts may break or stretch causing new head gaskets to leak or blow out.

take the heads to an engine shop, have them magnafluxed for cracks and check/ground for flatness and new sealing surface.
Cologne series 4L heads are notorious for for cracking.

have valve seats checked for cracks and regression and when ok, have 3 angle grind done for best seal long valve life.

if the block decks are not reground for level and proper finish, i like to lightly grind the block deck with 80 grit corborundum paper to slightly roughen the surface for better head gasket grip. use rags to plug the cyl holes from grit.
Ford used much too smooth a surface on head and deck surfaces especially in the very narrow inter piston area.

these engines would be prime candidates for deck steel ring insert grooving for far better head gasket sealing but far too expensive in an old road warrior rig.

 

My 94 had a similar problem. I had an intake leak for years. I took it to the dealer for repair. They fixed the leak and it still ran like crap.. The heads were shot. The valves beat the seats to death and the heads were cracked..Put new heads on it and it ran fine..


Dick

 

I'd bet on a head. You'll have to pull the head to replace the gasket, so check it out whill it's off. This sounds like more than just a bad gasket.