I have a 85 Montero with 2.6l four banger and five speed tranny .... has AC but not hooked up and no belt installed.

The heater makes good interior heat .... very good as a matter of fact. So good thermostat ???

I am losing antifreeze somewhere ...... at the recovery bottle mostly .... I can find no other leaks. Don't seem to be any antifreeze in the oil ... or oil in the antifreeze.

Every so often .... more and more with the onset of cold weather .... the coolant recovery bottle lid just seems to blow off the bottle .... there goes my antifreeze in a cloud of steam ... once this happens the temp gauge will go up (but not into the red) and the heater temp gets less ... less but not cold .... still warm.

I have watched coolant flow thru the radiator with the cap off and the flow don't look real good .... the water pump is only 'bout a year or so old. With the cap off and radiator full the flow continuously pushes coolant out of the radiator .... it never seems to quit till the radiator is about a half a gallon or so low ????

So what's up ??? Sticky thermostat ? Bad radiator cap ? Hoses seem to be fine ??? water pump don't seem to leak or make noise. Heater works good . I dunno ????

I'm gonna replace the thermostat and rad cap just for good measure but ... well this is kindof weird .... and I work with a weird coolant system on Pontiac Fieros all the time ... who knows <img src="/forums/images/graemlins/zombie.gif" alt="" />

Something is causing an excessive buildup of pressure in the system and it's blowing off the cap on the recovery bottle ??????? <img src="/forums/images/graemlins/scared.gif" alt="" />

Blocked rad passages.

You can get it "rodded" to clear it up, but the top of the rad needs to be removed and replaced by the rad repair shop that does the rodding.

Head gasket, perhaps..... pressurizing the cooling system with combustion gases. If that's what it is, it'll soon take the radiator along with it as the pressure splits open the radiator core or hoses.

It's also possible the thermostat is stuck partially closed (reason your heater works so well?).... if you're lucky, that's all it is. I'd first try replacing the radiator cap and thermostat and see what happens. It's cheaper to test, but for no more than they cost, you'll want them anyway if you have the radiator rodded or the head gasket replaced.

Frank

The 2.6L cooling system is far from rocket science. Even I can understand it. <img src="/forums/images/graemlins/smile.gif" alt="" /> When that system starts acting squirrley, itÆs easy to repair. YouÆll need to take several steps at one time to restore max efficiency to the system.

First, pull your radiator and have it rodded out. A good shop will do it for $65 - $75. Well worth the money. Secondly, get an OE thermostat. Many on this board will put aftermarkets on, but IÆm a bit more conservative. I want whatÆs supposed to be there on my ride. Replace your upper and lower hoses. Cheap û no brainer. Replace the tube that runs from the rad over to your overflow bottle. Check your bottle and make sure that cap fits like itÆs supposed to. Plastic that old can become brittle and crack. Replace the radiator cap. Cheap û no brainer II.

ItÆs possible the temperature sending unitÆs going south as well. TheyÆre pretty cheap, but IÆd do the rest of the above first and IÆD DO IT ALL.

Good luck and let us know how it turns out. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Do what dadrab says, thats what I did and worked very well.

Does it purge the bottle when cold?

rocket science .... LMAO <img src="/forums/images/graemlins/lol.gif" alt="" />

Yes it does purge the overflow bottle when cold <img src="/forums/images/graemlins/barf.gif" alt="" />

Just got back from the auto parts with my new thermostat, gasket and rad cap .... after dinner I'll install and test.

I'm thinking the blocked radiator thing is the correct answer ...... I'll let Y'all know !

Thanks for the replies <img src="/forums/images/graemlins/cheers.gif" alt="" />

Where is your temp needle during regular driving conditions?
If it goes anywhere above the half mark you have issues.

Check the fan clutch after driving a while. Turn the engine off and try to spin the fan. If it goes more that a 1/4 turn or so it's going bad. OEM is the way to go on this part, I have seen many post about aftermarket ones not working after a year.

Your Radiator is 20 years old so it's time to take it to the shop.

<img src="/forums/images/graemlins/patriot.gif" alt="" />

Could well be. I know mine was nasty when I had it done last year and my truck's newer than yours.

Well since the thermostat is closed when the motor is cold you should get no flow to the radiator so even if it was clogged it would not cause the cap to let out pressure.

So if the T stat is closed cold you either have a bad radiator cap or combustion pressure in the cooling jacket. If your cooling hoses get hard very quickly on a cold start its probably a cracked head. The head crack seals when the motor gets hot as the chamber expands.

Typically if you have a head crack one plug will read differently and you will have a miss at cold idle.

Kevin