Clatter noise on start-up.
 

On my new (used) 1999 Blazer LS, I get a somewhat loud "clattering" sound for about 15 to 30 seconds on, what seems to be, the first morning start-up. I am dealing with sub-zero temperatures here, so it may happen again in a few hours if the vehicle isn't driven. The noise seems to quickly go away, then seems to idle smoothly afterward.

I am about to replace the Spider fuel injectors. Is there something I should replace or repair at that time? I am familiar with the old EGR (I think) valve that would rattle/clatter at times. Could it be a dreaded lifter problem, or something serious like that?

Thanks for your ideas & feedback.

Sounds like it doesn't idle well when it's first started as well. If that is the case I would suspect that your lifters are leaking down, and the noise you here is there untill they pump up.

When the lower intake manifold gaskets leak coolant internally, (very common on this engine) the coolant will dilute the oil. The thinned out oil makes its way to the lifters, and they clatter cold. If that's the problem, and you take care of it right away and change the oil & oil filter, it might be OK. Check the underside of the oil fill cap, if it has a white, or brown foamy, milkshake looking slime, or condensation, the intake gaskets are probably the issue.

^^hes got a point. but id try changing oil first. go with some 5w30 synthetic blend and see if it shuts up. cold climates can do hell on engines.

Clatter noise (cont.)
 

Thanks for the ideas to date.

My oil cap looks clean. No foam or sign of condensation. The oil looks, smells and feels good. Generally, there seems to be no coolent smell or manifold leak signs that I can see.

Keep the ideas coming. What about the EGR or water pump, etc. ???

Mine was doing the same clatter sound. Noticed antifreeze leak and off color yellow residue in oil cap. Fixed manifold gaskets, upgraded spider injector, changed water pump, changed valve cover gaskets (noticed driver side had alot of slim junk inside), replaced EGR valve, basic tune up with all ACDelco and changed oil 5w-30 Mobile 1 high mileage. No more clatter.

Tuna, keep an eye on your coolant level, if you have to keep adding coolant, and can't see any leaks, it's probably the intake gaskets.

Thanks guys. All sounds like great advice. I did top off the coolant level and marked a line. Will watch for signs. I am awaiting a new MPFI Spider now. I'm wondering if I should just pull the intack manifold off, plenum and all, and do all the work on a bench. Then just replace the manifold gasket anyway. There is about 145 K on the vehicle. i don't know if the gasket was ever replaced yet. Would it be that much more of a job?

It's not that much more of a job. Just be sure you mark the distributor before you remove it from the engine. If you have Dex-Cool coolant (orange) I would get that out and put the green anti-freeze back in. That's what destroyed my intake gasket and water pump and radiator hoses and thermostat...alot of "and" I know.

I had the same issue with mine. My intake gaskets were leaking.

Here is a video I found on youtube that helped me through the process of getting the intake out.