Cracked head

[pete]

After doing the head gasket last year on my 94 AWD non supercharged engine, I went 550 miles and my head cracked in three places. Or maybe they just got bigger. There are now three obvious hair line fractures: Two of them at the #3 spark plug hole on combustion chamber side;These start at the plug hole and go into each of the two exhaust valve seats at that cylinder. The other one goes from the intake valve seat to the exhaust valve seat on the rear end of engines #3 combustion chamber. See the three red marks on this picture below to the rt.

car pictures 031.jpg previa cylinder head.jpg

when i took the exhaust apart just under the manifold, coolant came spilling out. You can see from this picture how much coolant was getting into the combustion chamber by the steam cleaned piston #3.

car pictures 033.jpg

I don't see any evidence of coolant getting through the used gasket here:

car pictures 035.jpgcar pictures 034.jpgcar pictures 033.jpg

I did notice when i loosened the head bolts they were only torqued down to 680"lb.

This seemed too low to me and could be why it cracked???

Anyone got a good cylinder head for my Previa?

[pete]

You might be able to see the three tiny cracks if you click on either one of these pics:

previa cylinder head 003.jpgprevia cylinder head 001.jpgprevia cylinder head 002.jpg




It too late to know if the cracks were starting before. Like i already mentioned, it did make it 500 plus miles into my road trip before showing a temp problem. Then things went bad really quick.

Should have done a "QA inspection cleaner" test for any evidence of the start of these tiny fractures. I think they were there before but just invisible. Any Ideas?

[timsrv]

That's a lot of wasted work. I hate doing jobs twice, sorry you're having this problem. I've heard of Previa heads developing these cracks before. Thankfully I haven't had the misfortune yet (and hope I never do).

I did the head gasket on one of my Previas and frankly I was a little distressed with the head torquing procedure. The FSM said to torque them, then crank each bolt another 90 deg! This seemed like an outrageous amount of torque to me and I feared breaking a head bolt, but they all held and so far the van has been holding up fine. If I were in your position I would consider purchasing one of those "low mileage jap engines". Most major cities have an importer of these things and they are supposed to have less than 50k miles on them. If you're paying somebody else to do the job, your total cost would most likely be less too. Next time I need major engine work I'll most likely go that route. Good luck. Tim

[pete]

That confused me too about the 90 degree torque on the head bolts in the FSM.
Called the dealer and they want a grand for a new head and will take a month.

It was way easier to just drop engine down and pull the head.about 90 percent less to take apart(seems like 90.did not actually make a list) and won't have to deal with movin engine around too.

sounds like i'll look for a low miledge engine or just pull a head from the junk yard.

any ideas on what year heads are compatible?

[timsrv]

I'm not 100% sure on this but I believe all naturally aspirated heads are the same. Tim

PS: I'm getting one of those "low mileage" jap transmissions for my All-Trac and was considering getting an engine at the same time. Nothing wrong with my existing engine, just has a bunch of miles on it. I was thinking I could swap the set in one weekend then not revisit these things for a long time to come. Tim

[pete]

I just found a previa that this guy uses for work. The interior is shot and body is not that great but only 170,000 on engine and he wants $900.

I'm wondering if his engine and trans will work with my 94 all trac. his is a 93 2wd NA engine.

[timsrv]

I know there were a lot of changes between 93 & 94, but I don't think any of them affected the engines or trannys of naturally aspirated Previas. Like I said, I'm not 100% sure, but I'm at about 90% pushing 95%.

[pete]

even the same trans for 2wd and all trac? I could see the engines being the same. I just would not automatically think for transmission too.

[timsrv]

I would assume trannys stayed the same too.......of course you know what they say about the word ass u me . All-trac trannys are different from 2wd trannys, so you couldn't do a simple swap over there. I suspect the internal parts are mostly the same, but the back half of the cases and tail shafts are different. Tim

PS: Naturally aspirated trannys are different from supercharged trannys......SC trannys are built tougher and also use a different gear ratio.

[pete]

So being that the SC transmissions are tougher, maybe if i go the complete engine route instead of the quick fix of just a used head, then i should look for a SC hook up. Anyone ever done this? I know the computer would have to be swapped out. just curious what else. maybe its not worth it. I would like to have a tougher trans though.

[timsrv]

SC Previas utilize different gear ratios on the differential(s) to compensate for the gear ratio change in the transmission. You could use the SC tranny on a chassis that was originally NA if you also swapped out the differential(s) (or at least the gears inside). Personally I would prefer the engine to remain NA for economy/reliability reasons. SC engines seem to hold up okay, but there are more things that can go wrong. IMO the superchargers on these don't increase power a tremendous amount anyhow. Tim

[terbennett]

Here to chime in. You can buy a used JDM mileage engine for pretty cheap. I'm talking $600 or less. They are supposed to have low miles and they usually will come with a 6 month warranty too. They are pressure tested before they are sold. Most of these engines have low mies but noone really knows exactly how many miles are on them. You could have 30,000 miles or 80,000 miles. Most people will say 60,000 miles. Anyway, I've seen places here in So. California selling engine and auto tranny together for around $650. Previa trannies can be had for $200 or less. Most around here for the N/A van are going for around $150. BTW, check E-Bay. Many of the distributors are selling on there too.Good luck.

[timsrv]

The way it was described to me is Japan places a huge tax on vehicles that exceed 60k miles. Due to this tax it's often cheaper to salvage the vehicle and get a new one rather than keep it and pay the tax. This is what I was told by the JDM outfit in Lynwood, WA. Tim

[terbennett]

I couldn't remember if it was 60,000 miles or 60,000 kilometers. Thanks Tim.

[timsrv]

I couldn't remember if it was 60,000 miles or 60,000 kilometers. Thanks Tim.

That's a good point. The lady I talked to said miles..........perhaps she already converted from kilometers??? Perhaps she didn't know what she was talking about??? I've never really looked into this before, but I have friends that have used these and had really good luck. Maybe somebody else here has more info on these things? If so I'd like to find out more. For prices like that, I think I'm going to swap both the engine and tranny together. Tim

[pete]

Those are great prices. The ones i have been given so far from other internet parts places have been around $800 for my engine and another $800 for the trans. free shipping and warranty. there is no way i'm going to spend that much on an engine with 130,000 miles. A friend told me about http://www.car-part.com and there are some really cheap places to get used parts. That's probably where I will get the head. I don't see the point of pulling the motor and not put in newer, low miles, trans and engine.

[pete]

Just got a quote from internet jdm place. i waited 20 minutes on the phone and at first the sales guy told me they don't have motors that old. i pressed him and he said o yeah they have 3 motors but they don't have transmissions. 1 year warranty and less then 50,000 miles and provides vin #. They want $1950.00

[timsrv]

I can get the engine for $749 & the Transmission for $495 Both delivered to my door. The company I'm dealing with said they only have one or two transmissions at this time so I'm waiting on posting that company's info until after I get mine . They said the engine and tranny will come on 2 different pallets (not married together).

I talked to the woman there a little more about the mileage claims. She said that Japan taxes vehicles based on how many kilometers they have. As the kilometers go up, so does the tax. At some point (usually between 70,000 & 95,000 kilometers) the tax becomes too expensive and the vehicle gets recycled. They purchase engines and transmissions and have them shipped over here for resale. When you convert kilometers to miles, this works out to about 45k - 60k miles, but there's no way to really know for sure what the history was. I'm still a bit skeptical, but it does make sense considering the roads (or lack of them) in Japan. I think it would take a really long time to rack up the miles because they don't have a huge highway system like we do (it's an island). Tim

[pete]

To buy a refurbished head with valves and warranty is $350.00. I don't want to go this route. It will save time but not deal with the weak link of an overheated motor with a good head. If i'm going with the quick fix then a good used head with the same miles is all I need. But I want to put my hands on it before i buy it.

I found a van in a junk yard only a couple miles from me:

carpicspreviaandjunkyard 006.jpg

They say the lady drove it to the yard. I could see from the damage to the top rear that it was too costly a repair for her, but internally everything is fine from the wreck. Hardly anything has been parted off of this van. 200,000 on the odometer 2wd federal emissions NA engine built in December 1990. If we do this, then the compatibility question will be answered with a 03/94 NA motor.

They will sell me the whole engine for $250.00. The passenger side is sunk in the mud so to save on hours of labor time i'll just yank the head for $250.00. I have a power outlet and they will let me cut out the top above the engine with my diamond bit angle grinder to lift the intake then bend the paneling back and the head hopefully will come out the top. They won't sell the whole van and its future is the crusher, so I'm not so worried about cutting it up. If this quicker fix does not work then I'll consider to finish pulling the entire engine out or going with low miles JDM. $250.00 and the van going soon at 200,000 or $1300.00 way more labor and down time but with trans and motor at 60,000?

[pete]

I want to hear how this engine at the junk yard sounds before i pull it apart but not sure of the gas supply situation. The tank is sunk in the mud. I have a extra fuel pump from one of my plow trucks. It's a W series 87 dodge ram pickup. I have all the fuel connectors to go inline to the previa. Is this a stupid idea? I have never done a fuel pump and i can't find any electrical diagrams for how my dodge pump is supposed to be wired. Do These fuel pumps take 12v directly? I have all the plumbing and electrical components to do this. Obviously extreme caution must be taken when running voltage to a fuel container then fuel into a motor. It will be fun and exciting but maybe there is an easier way to check a junk yard motor without fuel supply.