Last night i was driving my 4.7L 2002 1500 and it blew the lower radiator hose. I first notice the engine running hot at about halfway between 12 oclock (normal) and the red line. I was on a long straight stretch of road and when i came to a stop sign and let off it died. There were no prior symptoms at that time unfortunately. No smell, no steam or smoking to alert me to stop. I had added water the day before because it was about half a gallon low and running hot at about the same level when i was towing. Anyway, i got a tow replaced the hose and its misfiring with p0307. I ran compression tests and below are the bad results. Im looking for opinions on the wet/dry differences and the overall low compression. I have 2 testers and they read the same.


1 - dry:60, wet:80
3 - dry:40, wet:65
5 - dry:240 (water), dry:30, dry: 50, wet: 80
7 - wet/dry:0
2 - wet/dry:90
4 - dry:60, wet:90
6 - dry:60, wet:90
8 - dry:50, wet:80

#4 confirmed blown hg, water in cylinder, leakdown bubbles radiator.
#7 unknown with leakdown. Not blowing in radiator or crankcase most likely valve issue IMO, seems to just blow right through. 0 compression confirmed by no compression sound during test.

So, all of the compression numbers are extremely low. They increase around 30psi with oil (i actually used gear oil as i only have atf+4 and 80wt gear oil on hand).
Im wondering if this is a ring issue or maybe just my heads got screwed up, so far i know i have the blown head gasket on passenger side #4, failed water pump gasket (and pump?), clean uncomtaminated oil, and no compression at all on #7.
Before running the tests i used for these numbers i tested a few cylinders with plugs on and didnt write the numbers down but when i tested cylinder 5 i got a 240psi reading and water. It may have been because i tested #4 right before but im not sure. I initially thought 5 was blown but putting air doesnt affect the radiator, obviously it has an issue though.

Btw, I dont have a proper leakdown guage just the compression tester. Tests were done all plugs off, wot, 5 cranks.

 

The engine is shot. Minimum spec for compression is 100 PSI, you don't even get that wet..... (aside from full of coolant.....) Wonder is you dropped some valve seats.... Need to tear it down, and see whats up.

 

Yep, i know, but im wondering how i can differentiate between a ring problem and head/gasket issues without a proper leakdown test.

Do you think valve seats or other head issues would cause a common low compression like that without it being a ring issue? I read a 10% difference dry/wet is the maximum allowance.... 60 and 90 is like a 33% difference but i even get that on cylinder 4 which i know is blowing into the radiator.

The teardown is in progress. 2 more hours till i remove the heads.

 

If you have multiple problems..... leakdown results might be meaningless. You may just wanna bite the bullet, and re-ring it as well. (along with bearings, gaskets, timing chains and gears, oil pump, etc.) Or, get a long block, and simply replace the whole thing.

 

Stuck valve at #7, probably seat came out and is holding it open.

 

Got some new heads installed since they were warped beyond machining spec. Seems to be running great now. Valve seat did come out and was holding that valve open.
Replaced water pump too. Im too broke to afford a new timing chain so i unfortunately didnt replace it but i did replace the broken tensioner on the main chain.

 

Just wanted to check in on my thread.

I never did any compression testing after installing the new heads, but when i got it together enough to safely start it fired right up. There was a bunch of radiator fluid in the tailpipe / muffler and it caused a lot of steam initially which made me think i was still screwed but it burned off and now i have driven about 800 miles on the new heads with no issues, although it does seem to be lacking some power. I think the heads i got just suck, they were from a junkyard and werent rebuilt.

 

Nice to hear your going down the road again. Thanks for updating

 

Yep. Thinking about doing a HO cam swap. My local junkyard has a jeep with the HO motor and they are $27 each.