Truck won't start, massive water leak from the back of the block, I'm stumped.

I've tried searching, and tried figuring it this out on my own, and with my roommate, an ASE-certified mechanic, and we are stumped.

So about 2 months ago, my truck didn't want to start until I let it sit for a while. On that same trip, it blew up the radiator (big crack on the top end tank).

I replaced the radiator, coils, and plug wires. It worked pretty well until about 2 weeks later when it started over heating. I didn't think much of it and added coolant, thinking I just forgot to burp the system when I replaced the radiator. since then, it's had a huge leak coming from the back of the block that I cannot find. I've moved the plastic wiring harness bracket (accidentally pulling the wires out of the coolant sensor that is underneath of it) to try and look for the leak, but I can't find it. The freeze plugs look dry, as does everything above the block/head mating line.

Unfortunately, that's not my only problem; it won't start now. It gets spark from both coils, the wires are in the right firing order, and we checked that the injectors are getting firing signals with injector lights. It would also start up and run with starting fluid if it was sprayed into the intake.

Using that knowledge, I changed the fuel pump, thinking that was the issue. It took a LONG time to crank, but it eventually caught hold and ran pretty well. I was able to make one round trip, then the next day it wouldn't start at all, no matter how much I cranked.



Cliffs: My truck won't run, and I can't find a coolant leak. It has good spark, good fuel pump, and good injector pulse. The coolant leak is the sneakiest damn thing I've ever tried to find.

It's a 99 2.7L 4x4 standard cab short-bed with an automatic.

 

Are you building pressure in the rad hose as the engine warms up ? Have you tried pressure testing the cooling system ?
There are frost plugs behind the flywheel . Is coolant hitting the ground or going out the exhaust pipe ?
I suspect a head gasket issue but this would need to be verified
I will throw you the FSM http://web.archive.org/web/20101127014333/http://ncttora.com/fsm/1996/96_repair_searchable.pdf

 

I tried finding the leak with a pressure tester, and it pissed out the back. I filled the system up completely with water for testing, and within half an hour of looking and pumping the system back up, it started spraying air out.

I can see puddles on the top of the transmission bell housing and I believe on the block itself. The water comes out from the exhaust side of the back of the block and hits the ground. There's a big enough leak that it drips from multiple spots.

Thanks for the FSM as well. My roommate has been looking through Mitchell on Demand as well.

 

That stuff is bad news for an engine. Your ASE mechanic friend should slap you around for using that.

 

Is there water in the Oil? Have you pulled the valve covers to check for water ?

 

He's the one that did it. It was a test to see if it was a fueling issue. in what way is it bad news? I wasn't driving around on it, it was just a temporary fuel for a start-up test.

There isn't any water in the oil, and no, I didn't pull the valve cover (singular).

 

After it stopped running the 2nd time, did you try starting it again with the starting fluid?

 

check compression, i hope im wrong but I bet your head is cracked unfortunately

 

no

i'll check that and try again tomorrow. I'm really more worried about the starting issue at the moment. if it can start, I can keep pumping water into it while still making money.

 

Like you mentioned earlier, if it starts again with starter fluid it certainly sounds like it's not getting fuel. Have you tried changing the fuel filter?

Also, double check that your mass air flow is connected. That will keep the truck from running if it's not plugged in.

 

I just checked the compression on cylinders 1 and 4 (before the battery died too much to check the other two) and they both show between 90 and 100 psi. The plugs smelled like fuel and the MAF is plugged in.

 

those numbers are encouraging but you really cant do a reliable test unless all 4 plugs are out and you have a good battery. it needs to turn over good and strong for compression testing.

still doesn't mean the head isn't cracked but its a good sign whatever it is isn't inside the cylinder area and "might" be fixable, might be as simple as a head gasket leaking from the water jacket

umm, I assumed you checked all your hoses but, are you sure you don't have a busted heater hose on the back of the block? its not easy to see that sucker in there

 

yeah, that was the first thing I checked. compared to where it looks like the leak is coming from, the hoses are easy to check!

 

The compression readings (all four plugs out this time ) are:
cyl 1: 120psi
cyl 2: 130psi
cyl 3: 110psi
cyl 4: 120psi

The battery is dead as hell, though, even with an overnight charge. I guess I'll be getting a new one and checking then.

 

Did you ever find the coolant leak? I've got one doing the same thing. It only leaks when it's running but it leaks pretty bad. However I cannot see or find where it's coming from. It looks to be below the head so not sure what to check