new engine noise

**TimMc** · 05-30-2008, 08:02 AM

All right folk this is my first post and I am looking for help. I have a 2004 GMC with the 5.3 in it. The engine got over heated with a coolant leak and now has a death rattle on start up. I does not do it once it has warmed up and it goes away withing 10 to 15 seconds. Power seems the same as before the over heat. The overheating was caused by low coolant level and that is another mystery. It was a gallon down and does not show any signs of leakage. Oils clean and nothing coming out the exhaust but normal water flow. Any ideas?

**Mr. Luos** · 05-30-2008, 08:03 AM

Politely ask it to shut up...like I do with the wife.

It sounds like the notorius piston slap. How long does it last on cold start-up?

**TimMc** · 05-30-2008, 08:04 AM

15-20seconds. Like it builds oil pressure and goes away.

**Mr. Luos** · 05-30-2008, 08:16 AM

Yeah...sounds like piston slap.

This is something GM calls 'normal,' although with the overheating incident, it could be a slightly burned piston.
Seem like it is the whole motor?

**TimMc** · 06-01-2008, 06:07 AM

might be - What is the life span before replacement? is there history or do I need to get fixed yesterday. I will probable look at buying a short block or long block if that's the case.

**SeVeReDiStOrTiOn** · 06-01-2008, 10:53 AM

Sounds like you have two seperate "problems"...the rattle sounds like piston slap like Luos said and is normal unfortunately.

Have you looked for dried coolant anywhere...if it was me i'd start around the water pump. The coolant might not be coming out the weep hole because the gaskets are known to go bad...if it is coming out the hole the pump is bad. That's the problem with dex cool...when its not properly maintained it gets very acidic. Once you find the leak and fix it, i'd flush the system before adding new dex.

**bigrondownhiller** · 06-02-2008, 01:39 PM

If you fill it again or flush it they put a dye for it. Then you will be able to use a black light to help find the source.

**Insert** · 06-02-2008, 04:35 PM

well... 1 gallon of coolant missing without finding any leaks... and the motor is running odd. i'd drain oil and look for coolant in oil.

**TimMc** · 06-03-2008, 07:42 AM

Thanks for the help. I will dig deeper and have an oil analysis run. have local shop that does it.

**TimMc** · 06-19-2008, 04:45 AM

The die has been in the coolant for over a week now and no signs of leaking and coolant level continues to drop on a regular basis. oil level has not changed and am waiting for the oil sample results to come back. So the mystery continues.