Replacing a Previa head gasket.

[tfreed1]

Although I want to minimize the work on this job, I decided I better at least replace the valve seals since I have the head off and there are so many miles on the engine. I'm glad I decided to do this as the valves for the cylinder that took the most water were pretty well stuck in the valve guides. I got them freed up. I still have a few valve seals to change. Makes me miss 2 valve per cylinder engines. I did not lap the valves as I don't want to deal with changing shims.

20190904_205641.jpg

Finished replacing the valve seals.
seals done.jpg

[tfreed1]

Cleaned up the block deck and it is in good shape other then the pitted area.
deck.jpg

After reading about possible options, I decided to use a small bit of JB Weld epoxy in the pitted area.It takes at least 15 hours to cure. I will file it flat before putting the gasket and head on.
pit.jpg

jb.jpg

Here is a SAAB TSB using this solution:
210_1797.PDF

[tfreed1]

I put on the gasket....
gasket on.jpg

Torqued the head bolts....
head torqued.jpg

And installed cams.
cams on.jpg

Will work on connecting all the peripherals and getting the job finished as time permits.

[timsrv]

Here is a SAAB TSB using this solution:
210_1797.PDF

Well that certainly makes me feel better about it. If I ever run into that situation I'll likely give it a try. Looking good! Thank you for the awesome documentation and please keep us posted on how things hold up . Tim

[tfreed1]

Thanks. The TSB made me feel better about it too.

Some additional information that may be helpful:
I drained the oil the day after the gasket blew and there was quite a bit of water in the oil pan. I drained the coolant and refilled the oil and cranked the fresh oil around the engine using the starter. I did not want to leave water in the oil passages for an extended period of time. When (fingers crossed) the engine starts, I plan on running it for a while and then changing the oil again. I plan on adding straight water first, then draining it before adding antifreeze.

[tfreed1]

I finished getting everything together and the engine is running well after a few minutes of smoke from the antifreeze in the exhaust and the oil I used while assembling the head. I ran the engine for about an hour to check for leaks and to boil off the remaining water from the inside of the engine. When it cools, I am going to change the oil, drain the water, and add antifreeze.

done.jpg

manifold done.jpg


I would estimate I've spent 35 hours of actual work time on this job. I spent time getting 26 year old bolts loosened and figuring out what needed to be taken out. I changed the front O2 sensor and had to drill out the studs that were too rusted to get out. I spent a lot of additional time researching how to deal with the head pitting.

o2 sensor.jpg

Leaving the engine in the van made the job possible to do on my own. I would not want to pull the engine without help. I also did not need anything other than a floor jack and jack stands to raise the van or the engine.

While under the van, I found these supports rusted on both sides and will repair them.

rust.jpg

I plan on using the van to commute to work and will let you know how it is doing.

[timsrv]

Awesome! Thanks for taking the time to document!

[Previologist]

I hope no news is good news.

[tfreed1]

I have driven the Previa about 1200 miles since replacing the head gasket and it is running fine. It seems to have a bit more power than before and the gas mileage has increased a bit as well. It has not lost any coolant or oil since the gasket repair. I am going to take it on a trip for the holidays (about 1800 miles round trip) and will give an update after that.

I replaced the third member with one from a 96 SC last spring and the rear end ratio is 3.73 rather than 4.30 which makes highway driving a bit quieter. I want to see if my highway gas mileage is any better when we go on the road trip. The acceleration is acceptable.

[tfreed1]

Drove the van on a trip about 1800 miles of highway driving and it is still running well. Have about 4000 miles with the new head gasket. Van has lost no oil or water.

[peaquod]

Hi Tim and everyone on this thread. Which is excellent. I’m getting geared up to run this gauntlet and I’ve noticed that since the first time i looked, the photos from the original repost have disappeared. Are they still available anywhere?

Thanks

Ethan

[originalkwyjibo]

Welcome to the forum Ethan.
The most current explanation starts on page 2 of this thread.

[tfreed1]

Hi Tim and everyone on this thread. Which is excellent. I’m getting geared up to run this gauntlet and I’ve noticed that since the first time i looked, the photos from the original repost have disappeared. Are they still available anywhere?

Thanks

Ethan

Hi Ethan,

The latest news on getting the photos back is here:
https://www.toyotavantech.com/forum/...ome-TVT-images

It looks like they will eventually be view-able again.


if you have any questions about the head gasket replacement, ask them here and someone should be able to help. Good luck.

Tony

[tfreed1]

Just an update

The Previa is still going strong 23,000 miles after the head gasket replacement. I have a new job that requires travel mostly around the east coast and been using the previa for work trips. I'm at 266 thousand miles now.

[tfreed1]

Another update:

Previa still running strong at 50K miles after head gasket replacement. Finally retired it as daily driver but use it when hauling is needed.

[Previologist]

Good news. That's a job I never want to do myself.

[tfreed1]

Head gasket blew after a bit over 50,000 miles. My wife was driving the Previa and pulled over after white smoke began spewing out of the exhaust. I drive over to assess the situation and got the van started. Since we were only a couple miles from home, I drove it home on 2 and a half cylinders and spewing steam like a mosquito abatement truck.
I planned on junking the Previa but got curious as to what caused the failure. Decided to take the head off and found the engine was good other than the head gasket. I did not take the advice of using a genuine Toyota head gasket last time. I used the cheap one from Amazon. After some forensic investigation, it looks like the gasket failed by rusting internally and allowing water to get into the number 4, 3, and 2 cylinders. The gasket seemed to get waterlogged where it was exposed to coolant.

20240414_172816.jpg20240414_172829.jpg20240414_172831.jpg20240414_172836.jpg


In both cases where the head gasket failed it was on the bottom or exhaust side of the cylinders. Pictures of other Previa head gasket failures I have seen are also in this location. I wonder if the head being mounted sideways is a factor in these failures. The weight of the head combined with vibration possibly pushes on the lower edge of the cylinders. The JB Weld fix for pitting near cylinder number 1 held up with no issues.

20240417_134107.jpg


Since I had done the job before, it only took about 20 hours to complete this time. I figure 20 hours work after 4.5 years is not bad. I used a Felpro head gasket this time. The old Previa is up and running again.

20240417_134123.jpg20240416_141413.jpg

[Previologist]

Thanks for the detailed writeup...That's a major bummer, and still something I hope I never have to do myself....but holy cow...you chose not to use a Toyota gasket again!? Well you'll be really good at this after the third time.

[tfreed1]

a. I'm a cheapskate
b. I like to experiment
c. I have a friend that was an engineer at Felpro

[rallycar_jepsen]

I'll be curious to see how long mine lasts. I also did not go with the Toyota OEM. I've got a bit under 15k on it so far. Working from home now so I'm not racking it up as quickly as I was when I was driving 300+ miles every week.

Whenever next time comes around I might try to see if I can do it with the engine still in the van like you've done. I'm glad I did the removal the first time around because it made it easier to do several other things I figured I'd do while I had it out, but I'm not exactly looking forward to repeating that whole affair in the driveway again.

Maybe I should go buy an OEM Toyota gasket to have ready on the shelf in case, while I know they're still available ...