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2.9l Burning Coolant - next steps


BlueBeardo

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I have a 1989 2.9l 4wd Manual Ranger that overheated last week. I let it cool down and drove it home to diagnose. I tried filling the radiator back up with coolant and instead watched coolant flow out of the water pump weep hole (or whatever it's called). I replaced the water pump and filled it back up with coolant. It seemed to be running much better, but I noticed I was burning coolant and going through it rather quickly. I checked the oil and it seemed to have coolant in it so I'm pretty sure either the head is cracked or the gasket is blown.

I've read through forums on here and the tech articles (all which are awesome) until my eyes bled and it seems the general consensus is that the head is cracked and it is almost never the gasket. Bummer.

I was planning on rebuilding the engine, but looking at the cost of a rebuild kit of about $500 for a full kit or $250 for just the re-ring kit plus the $400 dollar heads, things were really starting to add up. So I noticed almost every post about the 2.9 says just go ahead and swap out a 4.0L engine.

So I'm left with at a crossroads. This truck is my daily driver and I would like to keep it moving for the most days possible. I am okay with a couple weeks downtime if I need to though. Just not ideal. I've got two options:
1. Rebuild the 2.9l spending roughly $800 if the heads are cracked
2. Find a 4.0L and swap the motor with a mostly unknown cost. I'm guessing about the same, but I see a lot of "oh I guess I need that too".

I have some concerns about the 2.9l rebuild:
- Are the aftermarket/ebay heads worth it? Am I going to see this problem again shortly.
- I just replaced the water pump, alternator, starter, plugs, wires, and valve cover gaskets. I'd rather not just throw that time and money away.
- After reading about the 4.0l it sounds like I might be missing an opportunity.

And concerns about the 4.0l swap:
- I did some craigslist searching, and while I found some junkyard vehicles, I'm concerned about the life of the engine. Am I just swapping one set of problems for another? I don't really know how those engines ran.
- My best bet is to also rebuild that engine first since it is out. Just adds to the cost.
- Do I need to replace the manual transmission also? I've seen some yes's and some no's in this area.
- This seems much more complicated and work intensive than just fixing the decent motor I have (minus the coolant guzzling feature)

I guess I'm looking for a little help talking through this and to find my ideal path. Maybe also some input on the head leaking and some things to look for.
 


RonD

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reason for 4.0l swap is strictly for more power and torque, you also need to swap computer and engine wiring harness, also switch to MAF sensor instead of MAP sensor.
4.0l computer needs to be 1990-1994 and from manual trans Ranger.

1989 2.9l 4x4 should have FM146 5-speed trans, the M5OD-R1 is a better trans, but FM146 did run along time if maintained.
M5OD needs to be from a 4.0l 4x4

The 2.9l and 4.0l share the same block, so trans from one will fit the other.
If you switch to 4.0l then for sure get M5OD, if not then stay with FM146 until/if it starts having a problem, IMO.

A rebuilt 2.9l would be better than a used 4.0l, but really up to you.
Both engines had weak spots in the heads, so both tend to crack if overheated.

I would have the heads pressure checked before making the decision, of a rebuild or swap, get the actual costs for rebuild and swap.

Good read here on the 2.9l: http://www.therangerstation.com/tech_library/2_9_Page.shtml
 
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BlueBeardo

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I felt like the smartest choice was to rebuild the 2.9L. A new twist today was I went to check the coolant in the radiator to make sure it was not leaking out of the engine and only burning it and I found a good amount of oil in the coolant. It was enough that I could see it in the coolant. I'm pretty sure there is a crack the size of a canyon in my cylinder head. Not unless there is something else that can cause that.

After seeing that there is no way I'm driving the truck anywhere. I'm just going to start tearing into it like you suggest and get a look at the head before I make a decision.

Two other questions:
Is it really necessary to do a full master rebuild kit from here or is the Re-Ring kit adequate? What should I be looking at to make that decision.

Has anyone had any experience with these replacement heads? Is there anything I should be looking for?
 

RonD

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Is there coolant in the oil?
that's the deciding factor because it will ruin the bearings over time.
The coolant steams in the bearings and cleans off the oil, lol, not a good thing for lubrication :)

If oil is OK then really up to you, to re-ring you have to pull the connecting rods and new rod bearings are not that much, so............
 

BlueBeardo

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There is coolant in the oil in the oil. I started tearing apart the motor last night. I haven't gotten into the engine yet, but two of my spark plugs have leaks around them that look like coolant and oil.

When you said coolant in the oil is the deciding factor, do you mean between what kit I should choose? The re-ring kit includes the main bearings and the rod bearings. It doesn't include the cam bearings. If I don't do the full kit, would those be a good idea to add?
 

RonD

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Yes, all the bearings, they would all get "washed" by the coolant.

Also put in a new oil pump, always a good idea when you have access to it.
 

BlueBeardo

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I've got the heads off and out to get magnafluxed. I was going to pull the engine because either way it either needs to come out and get replaced or out to get worked on. Since the cylinder heads are out, what is the best place to attach the engine hoist to? Should I put a couple of the heads bolts back in the engine and attach to those.
 

2trux

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Since you have to replace the head bolts anyway that is what I would do.
 

RonD

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Probably be OK but they won't go in all the way and could bend and snap off.

Try using larger nuts or ??, on the longer bolts to hold chain or strap tight against block, that would prevent possible bending.
 

BlueBeardo

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Got the heads back from magnafluxing. They are both cracked in the same spot. Engine got pretty hot. You can see the crack by the greenish dust. The crack goes almost all the way around the head.

Should I be concerned about my block being cracked if both heads cracked?
 

RonD

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I wouldn't be to concerned about the block.
Heads get much hotter, especially if coolant gets low.

Cracks come from metal expanding when heated, head and block both expand when coolant is running at 190-230degF, and the shrink when they cool down to outside temp.
So this is normal.

But if coolant should get low or water pump stops circulating coolant, the head temp can jump to 280-300degF and that expands the metal too much on some heads and it cracks.
The block can crack it just isn't very common because even if coolant is low block will still have coolant, so doesn't get anywhere near as hot as a head will
 

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