My turbo 1000 is running a bit hotter than it used to even in the same ambient tempuratures. It all started one day when it was raining and I figured the loose fan belt tensioner was the prob. Fixed that and it's better but not what it used to be. Idle or low load temps are fine but any real street driving and it goes up to about 100ish on the guage. Before it stayed right at 80 maybe climb a little on a steep grade. I did a full flush. Changed the thermostat and spent over an hour straightening fins on the rad. It also seems to have to cycle a bit before it gets hot. It's fine for the first few minutes of running at temp. I have a couple theories but they may not make sense. First one is radiator cap releasing pressure too early and not allowing air back in creating a slight vacuum that might make the lower hose collapse. Second one is fuel quality. This condition started within minutes of getting fuel and I'm still on that tank. Is that even possible? My third theory is obviously the radiator (what's left!) After I return from the run most of the radiator is warm but not the lower half for about 6 rows in the middle. Clog? Just seems strange that a radiator would clog all of a sudden. I read about the vanes rotting off the water pump. How common is that? Is there a way to check water pump flow without pulling the pump? What is the pressure rating of the stock radiator cap? I'm going to change that and the lower hose along with have the radiator flow tested tomorrow.
It never dawned on me when I was talking to you on the phone about this a couple weeks ago, but it might not actually be running hot... I have seen the temp gauge get a bad connection and show hotter than the truck is on a few diesel mogs. It is usually something that just happens one day, then continues on a regular basis. Try getting the temp up to 100 and tapping on the gauge face with a screwdriver handle... A couple Mogs I had with gauge problems would drop back to normal if you tapped on the gauge. It might be worth getting an actual read with an infired temp gauge or moving the connections around on the temp gauge once the temp is up and see if the reading drops.
Once the flow rate is confirmed, that should rule or confirm the water pump and/or radiator. There should not be a cold spot in the radiator, but that should not just cause the heat to go up all of a sudden, more of a gradual type thing.
I think the radiator cap is a 16 psi unit, but i will check my manuals and let you know.
Cheers,
Ben
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People freak out when I drive into the shop with a perfectly good Mercedes, only to start cutting it up for parts. I just tell them that something has to die inorder to keep all of the other Benz's running.
That is one thing I was thinking too but forgot to mention. I did notice on the guage that the reading is dependent on electrical load. When I switch on the headlights or other consumer the reading goes up a bit. Basically less voltage on that circuit. I have a spare autometer coolant guage from my VW and was thinking of a temporary hookup to see if the temp actually is going up. Any insight on the idea of fuel quality. Unless it's just a coincidence the truck has only done this on this one tank of fuel.
just did a bit more tinkering today. I had the pressure washer out for the boat and the mog was right there so I gave the rad a blast. Put some actual coolant in instead of the water I've been running the past couple days for testing. Went for a drive and filled up the tank with fresh fuel from a different station. (6 cents more than my normal station!) No change. While driving I gave the guage thing a thought but I really don't think thats an issue. While driving around town in traffic the temp reads normal. Straight horizontal gauge. Once I get it onto open road and start cruizing is when the temp goes up. Slow back down at lights and if I'm there long enough the temp comes back down. While cruising at high temp I pulled over and pulled off the grille to feel around. I underestimated the cold spot on the rad. About 20 percent of the middle bottom of the rad is cold. Upper tank is HOT lower tank is warm. The truck isn't really running that hot but it's just different behavior than it used to do. The temp never goes abouve the line that is the 3/4 mark which I think is 100. But right now the temps are mild and the mog is unloaded. I plan to tow on hot days and would like some head room. I think a re-core is in my future. Or at least a rodding out but the core shows some signs of seepage so I think I should just do it for the peace of mind.
My 406 ran hot after a radiator recore. I replaced the t-stat (drilled a 1/16" hole in it for air to escape), flushed the heat circuit, drained the radiator, filtered the removed coolant (was new when I replaced radiator) and added water wetter to coolant and refilled. Temps went from 95-100c to 80-85c (where it used to be). Also check the surge tank lines (even inside the tank) for obstructions. Also, make sure the entire system is purged of air.
My 406 ran hot after a radiator recore. I replaced the t-stat (drilled a 1/16" hole in it for air to escape), flushed the heat circuit, drained the radiator, filtered the removed coolant (was new when I replaced radiator) and added water wetter to coolant and refilled. Temps went from 95-100c to 80-85c (where it used to be). Also check the surge tank lines (even inside the tank) for obstructions. Also, make sure the entire system is purged of air.
All excellent advice. I had a big v8 in an old Landcruiser years ago, and found that redline water wetter was good for 10 degrees less on the gauge, as the stock rad wasn't realy big enough. Use some quality coolant flush and you'll probably be amazed at the amount of crusties that get washed out.
Due to the big cold spot I just pulled the radiator today. There was over a liter of water that would not drain out the bottom. I had to tip it over to fully drain it and the stuff that came out was pretty murky considering I've flushed the truck with the heater hose T and a garden hose about 3 total times. I'm pretty sure there was no air in the system. I will toss in some water wetter as it helped me in other cars. Right now I'm trying to decide between a re-core of this one or a custom aluminum. Preliminary investigation seems that an aluminum might be cheaper due to the price of just the raw metal required to make the core for the original. On another note after looking closely at the fan shroud it appears that it was slightly altered for a larger radiator at some point. It looks about 3" taller than original. If anyone wants pictures of an SBU without a radiator or fan assembly now is the time. I'll snap some if theres interest.
A bit of an update. I got the new radiator in yesterday. Man is this thing beautiful! It really is a piece of art. I'm very impressed with the craftsmanship. The guys at Tapp inc. built it for me. It is a 2 row. The rows are I think each 1.25" the total core is about an inch thicker than the old one and has more fins also. It's a tad taller but clears the hood by about half an inch. I'm quite confident in it's cooling capacity. The total was 610 with shipping which I thought was very reasonable.
While the radiator was out I ran a garden hose through all available ports but didn't get much crud out. I had already flushed a lot before. But it still runs hot. Not as hot but still more than when I got the truck. I'm not sore about replacing the radiator because it needed to be done anyway. I was just hoping it would cure the issue.
I have still not put a real gauge on it (I had the wrong sender) I did check the connections to the stock gauge and they seem good. I cleaned the contacts for the fuse which powers it. I guess the only things left (if indeed it is running hot and it's not just the gauge) are that I'm making too much heat or not moving enough water with the pump.
The EGT gauge is mostly installed. I just have to drill in the probe and its done. That will tell me if I'm overfueled. I just don't see how all of a sudden it would be overfueling?
It's not that I'm lazy (well maybe) but is there a way to see if I the pump is good without pulling it? I get good heat in the cab and both the upper and lower hoses of the rad are hot.
Thanks to whoever has the attention span to read all that and also for any further insight. I know I should have done the gauge first but I'm a slacker.
Not as hot but still more than when I got the truck. I'm not sore about replacing the radiator because it needed to be done anyway. I was just hoping it would cure the issue. 
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