Overheated engine


tanbuddy

tanbuddy

15+ Year Member

Joined
Aug 16, 2007
Messages
446
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3,101
Age
45
City
Poconos, Pa
Vehicle Year
1989
Transmission
Manual
My truck has been going through antifreeze for a while, the other night when it was 5 below out it started getting hot, and puked it all out. I pulled over and dumped some mix in there but it still runs like shit, has a bad miss and shakes bad under 2000 rpm. Im pretty sure the head gasket is gone, maybe the haed too. Im gonna do a compression and leakdown test and go from there then.
WHere do these heads usually crack or warp first? Im trying to fix this thing for under a few hundred bucks so if i can get away with the gasket that would be cool.
 
ya the compression test should tell you which cylinder it close too. sounds like maybe a bad plug or wire too though. let us know
 
dgndngrngr said:
ya the compression test should tell you which cylinder it close too. sounds like maybe a bad plug or wire too though. let us know
Click to expand...

Im not incredibly mechanically inclined but why would a bad plug or wire make it leak coolant?

From what iv'e read on this site, heads are not too uncommon to crack but could also just be a gasket. Do a compresion test, figure out where your losing compression, you probably only need to do one side.(like 30 bucks if you do the work youself) its fairly easy, harder if you have A/C, but still possible.
 
If it is eating coolant, stop driving ASAP. There is no sense having to do a complete rebuild because the oil has coolant in it.

Plug wires/plug would not cause a coolant leak, and it sounds just like a cracked head/ blown gasket. I am going to said it is most likely a head, as the early stock 2.9L heads sucked. From what I hear though, the European heads are much better and tougher.
Nick
 
I drained the oil today to get that water and coolant out of there. Gonna do a compresiion test tomorrow. I think the truck has the better heads, i know they were replaced by the origional owner at 100 000.
Is there a way to tell if there craked without magnafluxign them? I could imagine that costing as much as a used head but ive never really checked into it before. Ill change the head gasket if its blown, but if the heads are bad ill probablly get a used engine for it. The bottom end is origional with over 200 000 on it. Or maybe a 4.0 swap if i find a cheap explorer. right now im hoping for just a bad gasket.
 
Other then compression testing them to help pin point where it is, no. You need to magnafluxing them.
Nick
 
the compression test will tell you whats goin on. if any cylinder is down 20%(or more) of the others, theres your crack.

i just thought it could have been a misfiring plug AND a coolant leak. yes, two unrelated things but i had an 89 taurus with the 3.8 and 2 blown head gaskets and she ran fine besides taking on alot of coolant.

like the fox said, if you can, dont drive it. the coolant will eat the camshaft bearings for breakfast
 
FWIW, head gasket failures are pretty rare........heads usually go first. Especially if its been run hot or overheated........
 
OK i did the compression test tonight, all the cylinders were about 175, except number 5, that was 160. That should still be good enough to run decent i would think.
I did a leakdown test too, cylinders 1,2,3 were around 75% ok. Cyl 6 was good too at 80%, but number 4 and 5 were low, only 55- 65%.

It should run with the good compression right? I dont know about the leakdown what that means or where the figures should be.

Plug 6 was a little oily too, so ill change that and see if it helps.

Any ideas? The new oil didt look like it had any antifreeze in it since i changed it the other day so im stumped at the moment....:icon_confused:
 
compression sounds good. is the radiator in good shape? hows the coolant flow in the top hose of the radiator(when you pinch it do you feel a rush of coolant once you release it?). if not something might be clogging up the thermostat or its not opening. the oil on plug 6 means you have warn valve guides or piston rings and might be causing a misfire.
 
I checked the vacume on it today, warm it ran 17 pounds steady, if i held the rpm up higher it went a little higher and stayed steady. When i goosed it, it dropped pretty low, then when i let off it shot up to 20 something, which i think is pretty normal.
I re -did the compression test today with the engine warm and throttle at wot, still got good readings,between 170-185lbs :beer:even a little better than yesterday.
I re -did the leakdown too, the cylinder that was real bad yesterday was good today, i think i didnt have it at tdc when i did that one yesterady:icon_twisted:. THe 2nd worst cyl is the same, at 65%, or 35% leak, and the compression is coming out through the oil fill cap.

Ill check that rad hose tomorrow, the rad itself should be good, i put a new one in a few years ago. I'll start pulling the plug wires while its ideling to see which cyl is not firing tomorrow.
thanks for all the advice!:beer:
 
Last edited:
Cyl 6 isnt firing. Pulled the plug while it idled and rpm didnt change at all. That cyl had the best compression and leakdown on that side too.
 
Im gonna change the plugs this weekend, i dont think theres anything wrong wiht the dizzy, it doenst have many miles on it and it looks in good shape. Ill add some of that stop leak suff om the rad and see what happens. I found a used 2.9 about a mile from here so thats my backup plan.
 
Does the plug from the cyinder that has the most leak down look very clean like its been washed???
or is that the #6 plug that isn't firing?

If this thing was going through coolant like crazy....was it boiling out the overflow or out the engine area or out the tailpipe?

could have a bad frost plug or a raditator hose colapsing, maybe you adress these and i just missed it.



recheck the grounds and leads from the coil.
the pick-up coil (under the rotor inside the distributor), could also be weak not creating proper spark to be delivered
 
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