DC2 Thermostat Housing Won't Stop Leaking! Help!

Hey guys.

I'm having trouble with my thermostat gasket/housing leaking. it's a slow leak from what I can tell but I'm sick of it and want to fix it properly.

When I first changed my thermostat well over 6 months months ago i re-used the old gasket and it had a slight leak from then on, not sure if it was leaking beforehand. as we came into winter and I replaced my radiator cap with a spoon one cause my old one broke, the leak got worse.

so I replaced the thermostat gasket with a generic one. and it leaked still. so I drained all the coolant and put silicone sealant on the housing and a bit on the gasket. it stopped leaking for about three days, then started again.

when I realized that the gasket I was using was completely different from the OEM type, I went and picked up the proper one and drained my coolant again and put the new gasket on with sealant on both sides, also scraped and cleaned both mating surfaces beforehand. did up the bolts tight but not he-man tight. and it leaked the next day. WTF.

I've tried loosening and also tightening the bolts but it didn't make a difference.

The wierd thing is it only seems to seep out when the car stays idle for a long time after driving (overnight) but not while the engines running.

the sealant I use is the same stuff honda use in their workshop.

any ideas guys? I've gone through 15-20 litres of coolant trying to fix this, and I'm out of money now, it's getting really expensive and time consuming.....

all input will be much appreciated, and rep for any good ideas.

thanks in advance.

sure it isnt leaking from further up....such as the actual outlet hose and clamp right next to it ?

yeah i checked around the hose, no leakage. it collects at the bottom of the housing in the middle of the gap only.

thermofan switch is tight , above in the same housing too ?
All i can suggest is to start again - get a new honda thermostat and gasket - and remove your starter to make sure you are applying direct torque to the two little 10mm bolts. Next get a torch and scour the inner edge of the housing for grit or dirt or a small pebble or calcification - anything to cause a weeping hole in the gasket. Do this on both sides of teh housing and make sure its 100% flat ! You can also place a smear of liquid gasket around the edge to make sure. The 2 bolts are 10nm each - which is finger tight + a tiny bit with a ratchet or spanner.

good luck

thanks for the torque specs ben, I'll have a go at that but I don't have a torch unfortunately :(

haven't checked the switch but the coolant is only at the very bottom of the housing. I'll look anyway though.

should probably add that this morning I came out to my car to find a puddle of coolant on the fan housing just under the radiator cap. I'm starting to think I got ripped off for this spoon cap, being second hand, it could be the wrong one or not be sealing properly.. so I ordered a stock one from work and I'll see how that goes.

ok so 5 times now and still no success. this is fkn ridiculous.

this time I put a stock radiator cap on, removed the thermostat housing completely, inspected for any damage, scraped every last piece of debris off the mating surfaces and where the hose joins to it, wiped it down, put new gasket on thermostat, applied thin layer of sealant to both sides of the gasket, and a bit on the mating surfaces too (as instructed on the sealants packaging) put it all together, torqued it down to 10NM, pieced the car back together, filled her up and bled the air out of the system.

and the next day, the damn thing is leaking worse then before! WTF I was even using stronger sealant then last time because the OEM stuff wasn't doing the trick.

*VENT OVER*

so over these 5 attempts I've tried going tight on the bolts, gentle, to manufacturer spec, used OEM sealant, stronger sealant (permatex form a gasket No. 2 black) been through generic and OEM type gaskets and it just keeps leaking!

any ideas?

are you SURE it isnt leaking from above (coolant hose/s on the head , circulating to the ICAV etc) ?

POSITIVE. I also replaced the small hoses in that area recently and I'm 100% sure they aren't leaking.

help! anyone had this issue before?

I'm gonna try some stop leak in hope that it will fix this tiny leak. I don't like using additives but it's come to the point where I've got nothing else that I can think of.

(and benjamin I tried to rep you for being very helpful with torque specs etc. but it said I can't do it until I rep some others first. thanks man IOU +1 rep lol)