I have a 1995 Dodge Caravan with approximately 126,000 miles on it. I have owned this van since 2016, and it has never really run right. I have done a lot of work on this vehicle, most recently replacing the cylinder head, and doing a new head gasket and head bolts at the time (2017). I would have preferred to replace the entire engine, but I was living in an apartment complex, and simply did not have the ability to do a job of such magnitude there.
At the time, I noticed a lot of rust and pitting on the engine block mating surface in the rear left corner (between cylinder #1 and the corner water jacket). I did have the replacement head checked and resurfaced by a professional machine shop, but due to no ability to pull the rest of the motor, I had no choice but to hand sand the engine block mating surface. I used a piece of very flat tile to back the sandpaper, and was able to achieve a very smooth surface, but almost certainly exceeded the curvature limit which is measured in thousandths of an inch.
After about 8,000 miles, I am already starting to have some exhaust gases leaking into the coolant, and the temperature going up if I drive on the freeway. It should be noted that even before this problem occurred, this engine has had a noticeable miss at idle, and way more blow-by than any other engine that I have owned or worked on.
So I am not looking to rebuild this motor. Hence why I am considering the idea of using a sealant. I would like to keep the van running as best as possible while I complete the engine swap on my Sundance, and also while I source a replacement motor for the van. (This is the only vehicle I own which could be used to transport a motor home from a junkyard.)
I have seen various sealant products advertised online, ranging in price from less than $50 to as much as $130. Most appear to use sodium silicate or “water glass” but some claim to be polymer-based and not contain any silicates. One such silicate-free product is made by Titan and claims to bond well to aluminum, and flex with the aluminum.
Any advice on what (if anything) to use? Currently, the engine does not heat up past the 40% mark in “around town” driving, but it does heat up to 80% if I drive it on the freeway. If I lift up the lever on the radiator cap only a small amount of gas bubbles are released, not a steady stream. But it is definitely exhaust gases, and not un-purged air.