Coolant leak outside of bellhousing - NOT LIM gaskets
 

Hello,

I am trying to troubleshoot my girlfriends 2000 4WD 4.3 Blazer Auto.

Here is what has been done to the vehicle in the last 6 weeks in the order of oldest to most recent:

- Lower intake manifold gaskets, valve cover gaskets and t-stat done by a shop that I trust very well. They changed every gasket that came with the Felpro upgraded intake gasket kit.

- Fuel pump and filter changed out by myself due to low psi

- A/C compressor, accumulator, orifice tube and hoses changed out by myself due to compressor eating itself along with a flush of the hard lines, condenser and evaporator.

- Radiator was changed at same time as A/C rebuild due a leak on the drivers side tank where it was crimped to the core.

I checked the fluids in it the other day just for maintenance and the coolant was low. I was hoping that just some air from draining it during the radiator swap worked its way out of the system.

Topped it and the overflow tank up to proper levels. Then 2 days later, the girlfriend told me she saw some "smoke or steam" come from the hood's drivers side seam when she shut the car down when she got home from work. Looked it over and couldn't find anything obvious.

Today, when she came out from the grocery, there was a small puddle of coolant under the car. I went to her house, drove it around for a while and shut it off. After about 30 seconds after, coolant starts running down the bellhousing and drips of the exhaust Y-pipe. It is coming from the rear of the motor where the GM engineers managed to put everything so you can't see the rear of the head or block even with a mirror. The EGR tube jacketing apprears to be wet with either oil from the previously leaking valve covers or this new mystery coolant leak where it runs down behind the head.

There is no coolant in the usual spots from a lower intake leak or puddled up near the distributor base or oil sending unit. Seeing as how it has the new felpro gaskets in, I am currently assuming they are okay.

Does a 2000 4.3 have freeze plugs in the rear of the heads? That is the one view of a 2000 4.3 that does not seem to be anywhere on the internet.

Rockauto shows "cylinder head plugs", both threaded and press in, as available parts for the 2000 4.3

No the cylinder heads do not have freeze plugs in the front or rear, only other place it could be is the head gasket itself but not real common for external leaks.
Also, i think a couple of the intake bolts go into the water jacket, check around those rear bolts, i always put silicone on them, on the threaded end and a dab under the head to keep it sealed. The egr tube may be blocking your view of it but look at the very back intake bolt, hopefully its at least tight....

See pic.

^ I agree. GM shop manual instructs to chase the threads in the heads and on the bolts, (or replace them) then apply thread sealer to the bolts. The threads must be clean so the torque, which is critical on this engine, is accurate. Thread sealer is necessary for two reasons: one, to seal oil and coolant, and two, to keep the bolts from walking out due to the low torque on them. If the leak isn't coming from the heater core connections, it's something to do with the lower intake gasket replacement, or an excessively corroded lower intake manifold around the rear coolant port. Corrosion is very common if Dexcool is neglected, or ethylene glycol is used. If it's leaking at the bolt, you can try removing all eight bolts, chase the threads and apply thread sealer to the bolts. Then follow these instructions:

Attachment 31311

Dropped the blazer off at the mechanics last night who did the LIM gaskets.

He pulled his system pressure tester on it while it was cold so he could look around and not get burnt. He found the leak. The upper radiator hose was chaffed where it rests on the valve cover and had a small pinhole on it aimed exactly at the valley between the head and lower intake.

It managed to look exactly like a LIM gasket failure. Since I was trying to troubleshoot it while hot, I didn't think to move the hose. Oh well.

$50 for troubleshooting, parts and labor and no more leak. Going to pick up the car this afternoon.