1996 5vzfe misfire and overheat

[jcush87]

I have a 1996 4x4 sr5 v6 with about 190k on it. About a month ago I started to get an intermittent rough idle. Last week I was driving and the temp spiked up (no overheat alarm) I connected to the obd using torque and found terms rising as high as 240.

Then I got a p303 misfire in cylinder 3
Symptoms:
Losing coolant, causing overheat
Sometimes radiator is uniform temp, sometimes it is cool on the bottom and hot on top. It is most likely the original radiator.
Small amount of white steam out exhaust (not sure how much is normal) I don't get a big cloud when I hit the gas.
Engine oil doesn't seem milky (neither does transmission fluid)
Coolant doesn't seem oily.
With radiator cap off, if I fill to the top so it is just about pouring over, I get bubbles and steam
Misfire is sometimes very bad and sometimes unnoticeable

I have changed the thermostat, run a coolant flush, and replaced the injector in cylinder 3. The coolant was dirty but not black in color.


I'm guessing the water pump has 80k on it

At this point I'm thinking best case is blocked radiator and bad spark plug (I didn't think to pull it when I did the injector...)
Middle case is blown head gasket
Worst case is cracked head.

I'm not sure it is worthwhile dealing with a cracked head on this age truck though.

What should I do to narrow down my issue to find the source?

Thanks!

 

[thegipper]

Do a leak down test on all 6 cylinders, you'll know for sure whether you have a blown HG or not. Don't waste your time with a dye test kit or any of that nonsense, the leak down test is the gold standard.

My 97 had a small HG leak on #3 and nearly identical symptoms as you. Every other test was worthless until I did the leak down test. Once I pressurized cylinder #3, bubbles came out of the radiator.

I bought a wrecked 99 for parts and decided to swap in that engine instead of messing around with the heads. It's a ton of work but she's back on the road!

 

[phattyduck]

There is no alarm for engine temp - just the needle on the dash (which should start to rise around 215*F).

That sounds *exactly* like a head gasket leak to the cylinder. A bore scope down the #3 cylinder will probably show a clean spot on the piston due to the cleaning action of the water/coolant mix. The early 5vz's did have some head gasket issues...

A used motor is the easiest option.

-Charlie

 

[jcush87]

Well I got some time to do some more diagnostics. I did a compression check and when I got to cylinder 3, I cranked and coolant shot a few inches out of the top of the radiator. The ceramic on the plug was also discolored. I bought a gasket set with head bolts, and a water pump and timing belt kit. Should be fun!

 

[gamefreakgc]

Dang, that's rough. Be sure to have the head in question pressure tested by a machine shop before you slap it back on.

I might be pulling the heads off my motor next week as well!

 

[jcush87]

Got through taking the head off. Took a couple of evenings.
Timing belt cover and some other stuff off

Intake plenum off.

Lower intake off

Head off

Cylinder 3 nice and clean. The lower passages appeared to have old gasket material blocking them.

Old gasket. Cylinder 3 had missing material between cylinder and water passage. Cylinder 5 flaked apart in the same location on removal. A lot of gasket material seemed to have swelled into the coolant passages near where the gasket is damaged.

New gasket looks a bit different from the original. But everything lines up. Some water passages are circles instead of the larger elongated holes.

I bought this set from Amazon.
https://www.amazon.com/Evergreen-HS...ead+gasket&dpPl=1&dpID=519xsSoqlFL&ref=plSrch seemed to have good reviews.

From the deterioration of the head gasket, and since I have all the parts, I will probably do the drivers side head gasket as well.

I don't see any cracks in the head like I have seen in pictures of this motor type before. Should I still get it vacuum tested and milled @ $110 per head, or just clean them and reinstall?

 

[jcush87]

Any ideas, should I still send the heads out for a check if there is an obvious head gasket failure?

 

[thegipper]

I would still have them at least inspected at the machine shop. If they think the heads need work, so be it. If not, bonus.... The head could be warped but not cracked, you can't see that with the naked eye (unless you have a surface plate and a dial indicator).

It would seriously suck to put it all back together and find out a week later there was an issue with the head.

 

[Team_Jake]

Take the heads to a machine shop!! This shouldn’t even be a question, you gotta do it. Have them re-surface the heads and check for cracks. You gotta think of why your gasket failed in the first place - not too often is it an actual failure of the gasket itself, usually it is caused by the head warping since it’s aluminum and expands at different rates as it heats/cools since the block is steel and that can cause your gasket to fail or cause your head to crack.

I thought my head gasket was blown for the longest time, turned out to be a cracked head instead. Glad I had it checked...

 

[jcush87]

Well that was fun! I ended up getting the heads resurfaced for $100 for the pair, and one cylinder failed the vacuum check and I believe the shop replaced a valve seal for an additional $10. I put it all back together just to have a bad misfire that traced back to me missing the #6 injector electrical plug... Yeah the one that takes the most effort to reach! The #4 I jector electrical connector didn't snap on and needed a fix, and I think that is why I missed #6.

Other things I had to do during the work:
Use the srarter and a breaker bar on the crankshaft pulley nut against the frame to loosen the pulley bolt

Make a jig to hold the crank pulley out of a 2x6 and some 5 inch grade 8 bolts so I could tighten it.

I used some thick neon paint to mark hoses, head bolts and connectors along with the timing belt to get everything back in place.

I found this FSM document to be very useful as well. https://ether3al.com/runner96-02fsm/engine.html

It runs well now and I am glad I didn't scrap the truck or pay for the repair. I think I was in about $400 to $500 in parts and needed tools. I'm guessing it took me about 30 hours of work, but I am not highly experienced!

Thanks for the help and advice everyone!

 

[T4R2014]

Nice fix, I would've went straight to engine swap. Just curious, what coolant was/is in it? (Green or red)

 

[jcush87]

It had green I believe. Now it has water just flushing the system 1 last time. Then it will have green again.