Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
While taking care of many engine-related issues regarding this vehicle:
http://www.forums.IHPartsAmerica.com/readers-rides/4072-dd-known-chunk.html
I discovered the root cause of the randomly occurring situation where the engine temp would drop significantly while driving (as monitored on the oem temp gauge).
Given the fact that this high-dollar engine had been assembled 22 years ago in a most sloppy fashion (including installing the thermostat housing/water neck using the original oem gaskets slathered with rtv, blue on top and clear on the bottom), I was surprised to find the correct rs370 thermostat installed (180f setpoint). But when I lifted the thermostat out of it's counterbore, a chunk of "something" fell down inside the thermostat housing.
Once the tstat housing was unstuck and removed, I could see the object which appeared to be a piece of 3/4minus crushed rock that makes up our parking lot. But once I used the forceps to remove it and clean, I could tell it was a chunk of cast iron.
The 180f setpoint thermostat will be set aside for future use (after cleaning all the rtv off!), a fresh rs370 in a 190f setpoint will be installed. The 190 is an oddball in my collection of new rs370-spec items and over the years I've only had this one.
I remembered that when the two bolts that retain the thermostat housing/waterneck were removed, the bolt that also retains the a/c compressor brace was significantly longer than the other. I'd not seen that before on other vehicles. Since I never reuse those bolts, I picked out two new replacements and then cleaned up the water neck and housing and painted.
It was obvious that there was nothing missing inside the thermostat housing or water neck in the way of casting flash, etc. But when I looked down inside the water hole on the intake manifold the damage could be seen.
The passenger side bolt threads into a blind hole on the intake manifold casting. Because the bolt used was too long (by 1/2"), when the engine builder had installed it, the bolt had broken out the bottom of the casting , allowing the piece to fall down into the open area under the tstat housing. The flow of engine cooling then would allow the piece to simply bounce and float around in the coolant stream where on occasion it would land with the thermostat open and wedge the "can" segment in the open position, rendering the tstat inoperable in a random fashion.
The piece is barely able to fit through the passage inside the tstat housing casting where it could pass back and forth randomly.
The damaged section of the intake manifold is not a problem. But I'll use a sealant on the replacement bolt threads to prevent coolant migration past the threads.
The pic shows the broken piece of casting and down inside the manifold, you can see the section of the threaded boss that was broken away.
http://www.forums.IHPartsAmerica.com/readers-rides/4072-dd-known-chunk.html
I discovered the root cause of the randomly occurring situation where the engine temp would drop significantly while driving (as monitored on the oem temp gauge).
Given the fact that this high-dollar engine had been assembled 22 years ago in a most sloppy fashion (including installing the thermostat housing/water neck using the original oem gaskets slathered with rtv, blue on top and clear on the bottom), I was surprised to find the correct rs370 thermostat installed (180f setpoint). But when I lifted the thermostat out of it's counterbore, a chunk of "something" fell down inside the thermostat housing.
Once the tstat housing was unstuck and removed, I could see the object which appeared to be a piece of 3/4minus crushed rock that makes up our parking lot. But once I used the forceps to remove it and clean, I could tell it was a chunk of cast iron.
The 180f setpoint thermostat will be set aside for future use (after cleaning all the rtv off!), a fresh rs370 in a 190f setpoint will be installed. The 190 is an oddball in my collection of new rs370-spec items and over the years I've only had this one.
I remembered that when the two bolts that retain the thermostat housing/waterneck were removed, the bolt that also retains the a/c compressor brace was significantly longer than the other. I'd not seen that before on other vehicles. Since I never reuse those bolts, I picked out two new replacements and then cleaned up the water neck and housing and painted.
It was obvious that there was nothing missing inside the thermostat housing or water neck in the way of casting flash, etc. But when I looked down inside the water hole on the intake manifold the damage could be seen.
The passenger side bolt threads into a blind hole on the intake manifold casting. Because the bolt used was too long (by 1/2"), when the engine builder had installed it, the bolt had broken out the bottom of the casting , allowing the piece to fall down into the open area under the tstat housing. The flow of engine cooling then would allow the piece to simply bounce and float around in the coolant stream where on occasion it would land with the thermostat open and wedge the "can" segment in the open position, rendering the tstat inoperable in a random fashion.
The piece is barely able to fit through the passage inside the tstat housing casting where it could pass back and forth randomly.
The damaged section of the intake manifold is not a problem. But I'll use a sealant on the replacement bolt threads to prevent coolant migration past the threads.
The pic shows the broken piece of casting and down inside the manifold, you can see the section of the threaded boss that was broken away.
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