300 Tdi engine gurus..... a search of the forums didn't come up with any similar issue....
'87 D110 300 Tdi with manual 5 speed. I am fairly new to my D110 with it's 300 Tdi, but have owned my '95 D1 since new, have wrenched on my 911s for -gasp!- 40 years now, and have had my '52 Willys M38A1 Army jeep/matching '51 M100 1/4ton trailer for 38 years now- fully restored- do the parade thing, etc.
I bought my 110 from the PO in Connecticut last year in April 2013, and drove it back to Arizona last May. A family visit put me into Charlotte for a few days in route. Maybe a 100 miles north of there I started to get an overheat indication. A quick inspection revealed the coolant reservoir to be slightly low, but nothing appeared to be overly hot. Temp gage got worse, but nothing spectacular heat wise. Looking for any excuse to impose on the in-laws to the max extent, I honored the indication, and ended up replacing the thermostat and viscous fan clutch. Still indicated hot. Thinking I had one of the rubber impeller water pumps, I put in a new metal vane pump, taking out the metal vaned pump that was already in there- oh well.
The radiator was new, and I flushed out the block, heater core, and radiator too- all clean- no crapola flushed out. Put in all fresh 50/50 coolant. Also installed a $17 mechanical temp gage from Pep Boys- attached the gage to my snorkel, taped up the openings as I was going to be running in the rain for a while, and pressed on to Arizona. Culprit was the $9 temp sender. Again, oh well- cooling system is all new. All was well, ran about 190-192F all the way home.
Last week while running my son to school over in the next town, the thermostat started to open, then closed/got stuck? and the temp stayed in the red zone ( the cheap $17 mechanical gage had lived and died by this time, a short but useful life...). Outside airtemp was just below freezing, the indication didn't get worse, and was almost to school anyway. The thermostat tried to open several more times. I stopped at the local autoparts store, bought a gallon of 50/50 coolant. The engine was definitely getting hot. Carefully took off the res. cap- avoided getting blasted with the initial wave of steam, added coolant, and let the engine cool at idle out of the red and into the normal op zone, which for me in the mountains of eastern Az here, is about one needle width past half way on the LR temp gage. I borrowed the stores "Percussion Presuader" ball peen hammer- and rapped on the t-stat housing a few times, using standard Ford Motor Company procedures... I then pressed on for home, hoping the t-stat would free up some more- it didn't.
About half way back, I stopped, called, and had my wife come tow me home. I didn't want the engine to seize if they have the tendency to do that- I don't know what the 300 Tdi does. The engine was definitely hot, even with shutting it off and coasting down hill.
I let it cool until the next day, and adding coolant to the radiator, block plug by the t-stat housing, and the res to the fill line, all while bleeding the air off the radiator and block. The
300Tdi started right up with a minor "new sound" while cranking, that went away and haven't heard it since. Drove it up hill for a mile, and shazamm! right back into the redzone- shut it off, coasted back down hill right back to my garage.
Now, I'm thinking t-stat and water pump, with the possibility that something is blocking a hose, etc. Take everything apart again, flush everything, put in a new t-stat, waterpump is good- steel vane didn't fall off, no blockage in the hoses, no apparent blockages in the head- no oil in the coolant, no coolant in the oil- so the head gasket should be a-ok as well.
Flushed out the block with full throttle water from the house, then blew out everything with high pressure air, including all coolant from the heater core.
Put everything back together, all fresh coolant, purged the air from the radiator and block port by the t-stat housing. Turned the water pump by hand, trying to maybe move the coolant and purge anymore air for anywhere. Installed the serp.belt. No leaks anywhere.
Putting the coolant into the radiator and block resulted in over filling the reservoir by maybe and inch over the fill mark- no big deal I think, that extra fluid will fill any air pockets remaining, etc.
Cranked the engine, and within several minutes air pressure in the res has increased, the res. sounds like it has boiling liquid in it- I released the air pressure, coolant starts to boil over and out. Shut the engine off. Grab my digital pyrometer (if you don't have one- get one....- very cheap now)- coolant temp is 73F, I siphoned off coolant, the "boiling" continues in the res up until it's 94F, at which time I shut it down under the threat of my dinner getting fed to the dogs.
Air is getting injected into the coolant res- but from where? I siphoned out more coolant to get it down to just below the fill line, and after I shut the engine off, the remaining coolant in the res gets sucked out and down the hoses, leaving an empty reservoir.
What am I missing here? there may be an air pocket in the heater core still, but the t-stat hasn't had the temp to open yet to fill it.
Any words/thoughts would be greatly appreciated!