I have slow weeping leak in plastic Thermostat Housing and Outlet directly under EGR. It looks like oil, but could be coolant. There seems to be a hairline crack right at radius that very slowly weeps fluid, with engine hot/running. It is reddish in color, but doesn't steam/evaporate like coolant, which makes me think it's oil, but I could be wrong. I haven't taken it apart yet, but i assume it's one piece, not a seam at flange. It looks like maybe it cracked at radius when bolted/stressed. Anyone with ideas or similar experience, I'd appreciate hearing what you did. Could it be glued/epoxied/solvent welded in place? Thank you in advance.



2004 s-type 4.2 99k mi




Pic from part supplier. Have not removed mine yet. Looks like it's not quick job.

 

The plastic assembly develops hairline cracks and leaks orange coolant very slowly...it may not steam. The coolant can feel a bit oily.

Replace the entire assembly, which includes a new thermostat and temp sensor. This will only get worse and is a well know issue as they age. This will buy you another 10 years. I think it is a bit over $100. A patch is not the answer, and is playing Russian Roulette with the engine which is very intolerant of overheating should the problem worsen suddenly.

 

Thanks WhiteXKR! Now that's the kind of succinct, sensible advice I love this forum for. I've GOT to replace housing now! So I don't feel like an idiot.... crawling back here later with with an overheated/blown engine! Everyone will rightly say "We told you ......."