1998 F-150 appears to have "vapor lock"...How to Fix Problem?

Asked by Jul 09, 2013 at 05:47 AM about the 1998 Ford F-150 XL 4WD LB

Question type: Maintenance & Repair

I have removed and checked the starter... It's O.K...
I have checked the battery... It's O.K...
I have put a wrench on lower pully... It will turn only 25% each direction...
The vehicle has NEVER been abused, or driven over 3500 RPM...
It has its oil changed at Ford Dealership, and just turned 100K...
The motor is a 6-cylinder (4.2)

5 Answers

"Vapor lock" is a term I haven't heard used for a long time. You are talking about the battery, the starter, and 'turning the lower pulley"? That sounds more like hydrolocked than vapor locked. Vapor lock is an old term used before electric fuel pumps and fuel injection when an air bubble got in the fuel line, and all you had to do was wait 10 or 15 minutes and the car would start. But it would crank over easily. Hydrolocked is a blown head gasket when coolant gets in to a combustion chamber, both valves are closed and the engine is seized. I don't know if that is what happened here, just trying to make the distinction. So what's the deal? It won't crank over when you try to start it? Lets go from there..and you try to turn the engine at the harmonic balancer aka crank pulley and it won't move but a little bit? One thing you can do is pull out all the spark plugs and try to crank it over by hand or with regular starter for just a few seconds...see what happens. If coolant shoots out a spark plug hole it was hydrolocked.

Does your engine look like this? The reason I ask is the V6 4.2 has aluminum heads notorious for warping.

3 of 3 people found this helpful.
1,150

A warped head wont prevent the engine from turning. when you try to rotate the crank,(lower pulley) does it stop like its making hard contact with something or does it stop like its trying to compress? was there a knock when it last ran? pulling the spark plugs will relieve compression and possibly allow it to turn and will allow you to see into the cylinder. you may have "dropped" a valve into the cyl. which will deffinatly stop rotation

It is a "compression" problem...or some other type of "seizure"... Nothing "knocked"... Nothing is "hitting" inside cylinders... Can an AC pump seizure cause this amount of pressure... I will release the belt and see if things are "free" before going deeper... There was NO abuse to the motor... It ran without a "hitch" for 3-hours... Was turned-off... And, will not crank... RPM never over 3500... HOT weather was the only possible cure... All gages were scanned while driving... No electrical or idiot lights... No elevated temps in motor...

if one of the valve break it will be in the cylinder and would allow it to rotate to only certain degree but not all the way. thats one possible cause , it happened to me.

Your Answer

F-150

Looking for a Used F-150 in your area?

CarGurus has 179,994 nationwide F-150 listings starting at $1,300.

ZIP:

Ford F-150 Experts

  • #1
    OJ
    Reputation
    8,910
  • #2
    dandyoun
    Reputation
    4,540
  • #3
    tennisshoes
    Reputation
    3,060
View All

Related Models For Sale

Used Chevrolet Silverado 1500
2,101 Great Deals out of 167,326 listings starting at $1,888
Used GMC Sierra 1500
872 Great Deals out of 65,537 listings starting at $1,500
Used Ford F-250 Super Duty
378 Great Deals out of 43,934 listings starting at $2,400
Used Dodge Ram 1500
355 Great Deals out of 10,813 listings starting at $1,199
Used Toyota Tacoma
594 Great Deals out of 42,094 listings starting at $1,995
Used Ford Mustang
709 Great Deals out of 38,398 listings starting at $895
Used Ford F-250
454 listings starting at $1,800
Used Ford F-350 Super Duty
334 Great Deals out of 23,769 listings starting at $2,488
Used Chevrolet Tahoe
660 Great Deals out of 39,224 listings starting at $1,000
Used Ford Explorer
810 Great Deals out of 62,574 listings starting at $1,000

Used Cars For Sale

2018 Ford F-150 For Sale
27,619 listings starting at $20,990
2017 Ford F-150 For Sale
116 Great Deals out of 82,876 listings starting at $17,990
2016 Ford F-150 For Sale
119 Great Deals out of 7,637 listings starting at $18,989
2015 Ford F-150 For Sale
283 Great Deals out of 10,496 listings starting at $14,999
2014 Ford F-150 For Sale
429 Great Deals out of 13,638 listings starting at $10,849

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.