i parked my truck 2 years ago because of a massive coolant leak, about a gallon every other day.i was going to swap in a 6.0.when gas went to 3.50 a gallon i started getting second thoughts, so i started tearing it (99 4.8, close to 180k miles) down.a little backstory,this coolant leak never showed itself. not a drop anywhere to be seen. it wasnt in the oil, either.no steam out of the exhaust.it wasnt running hot. the only hint i had was a misfire on cylinder #5.best i could figure was that it might have been the head gasket, pissing into cylinder #5. so i got the heads off, and there was no sign of a leak, i figure a leak that big would be obvious to spot, were it the head gaskets.there was some water contaminated oil under the drivers side valve cover,at its rearmost. just a small bit. a guy here on the site mentioned something about cracked cylinder heads being an issue.has anyone had this problem? can you get aluminum heads checked for cracks? could it be the block? if it were the block, wouldnt that show up in the oil? i was looking forward to having this thing up and running again. guess i should start thinking about a swap again. my luck, whatever engine i end up with would be as big a piece of ****.

 

Yes a machine shop can pressure test the heads.. If the block was cracked inside, it would more then likely show in the oil, if it was outside you would see it on the ground.. My guess would be a cracked head.. Have them pressure tested..

 

ill look into that, thanks

 

look into the water pump... have seem them PUKE out of the weep hole..... then seal up just fine

 

i got word back from the machinist today, he pressure tested the heads... said they werent cracked. he did say that both heads were warped,and that the valves were leaking. he`s going to deck the heads and do a valve job.200 bucks all told. i asked if he thought the warped heads were the cause of my leak, said he thought so. what do you all think, warped heads=major coolant leak, a gallon every couple of days?i freakin hope so. this has been the most perplexing leak to diagnose. again, there was no sign of leakage outside of the engine. not a drop anywhere. there was no oil contamination visible on the dipstick. under the drivers side valve cover back where the pcv is, there was the slightest bit of contaminated oil. everything else looked fine.the water pump gaskets were a bit ugly, MAYBE some superficial seepage there,id think such a loss in coolant would be obvious there. nothing out of the weephole. that waterpump might have 30k miles on it, probably less. freeze plugs, cursory glance showed that they werent leaking.i might go insane if this thing still leaks after i put it back together. any opinions or input would be greatly appreciated. thanks again

 

Yes a warped head will leak fast. Now that you know the heads were warped you need to use a block straightedge and make sure the block itself is still true. With warped heads you can **** coolant into the cylinders, oil, or just out of the engine altogether. A cylinder leak will suck in a HUGE amount of coolant over time. If you see a piston that is especially caked in crud or has irregular burn marks, that's where the coolant went. The engine can also chug water in one or two cylinders without a serious performance decrease- or one you don't notice anyway as long as it doesn't cause an outright misfire.

 

thanks. i dont have a block straight edge, sounds pricey. can i use a level, or some other sort of straight edge?
i was having a misfire on cylinder 5, but it doesnt really look any worse than the others.the pistons are fairly clean, i was going to wipe off what crud there is... good or bad idea?

 

I'm guessing you had a water pump problem originally.

 

no,i replaced the water pump thinking it would fix a problem, which ended up being the radiator.

 

I am interested in seeing a picture of the pistions got one you can upload?