Tough overheating issue

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joe707

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Just bought a 95 Mark VIII that supposedly had a bad head gasket causing it to blow antifreeze out and overheat. I started with the basics and removed the thermostat and ran it without one. It ran in the middle of the normal range and being concerned about too much water going through the bypass hose I put a plug in that hose. It now ran in the low normal range and if sitting still it would go up to the mid range and the radiator fan would kick on and keep it there. I could drive the car anywhere now where before after about 3 miles it would overheat. So I bought a new thermostat to return the car to a normal condition. Realizing it was not the head gasket.
But it is doing the same thing. I removed the plug on top of the engine and filled it and the reservoir. It gets up the top of the hot range and the resevoir cap in not opening to let out water yet which make me think it is a cooling issue not a head gasket problem. I am guessing a head gasket problem would overpressurize the system and blow out the water, then overheat. But this is getting hot first. The radiator fan is working and will kick on. Hot water is getting to the heater core inside. None of the hoses are kinked. The system does hold pressure. When I start it cold no fluid come out the resevoir with the cap off. Again, makes me think it is not a head gasket. I am almost guessing the radiator needs flushed. It can cool it with enough water going thru but once u put a thermostat in it, even with it fully open, less water is being pumped thru.
Any guesses??? Thanks, Joe
 
My god man.... never run these engine without a t-stat or you WILL blow a head gasket! These are aluminum block and do NOT respond to heat or heat changes very well.

Ok, rant off. :)

To me it sounds like air trapped in the crossover tube. You must not fill the system at the reservoir. Open just the cross-over tube and see if you have air, if so fill it, runt eh engine - do not rev it - and repeat as necessary. Check it in a week again.

If there is no air in there, then we have another problem, likely water pump.
 
You won't blow a head gasket with running no thermostat... I did it for months in my 95 LSC and my friend has done it for years in his LS1 which is an aluminum block as well. With that said I still think having a colder thermostat is a better idea than no thermostat.
 
Had a similar problem with my 1996. Flushed the radiator several times. Installed new thermostat. Try as I might, I could not find a cooler thermostat than the factory unit. Nobody makes one. It really irritated me. None of that worked. The temp gauge stayed at the top all the time. Not quite in the "overheating" zone, but close. I finally ended up having to replace my battery as it was getting weak, and i had to replace my electric cooling fan because the motor locked up and kept blowing fuses. After replacing the battery and cooling fan, the temp gauge has been staying in the mid range. Before, it would stay at the very top of the gauge, but not quite in the red zone. Now it's fine. I don't get it, but it works for me.
 
There are plenty of cooler thermostats. Napa Thermostat #3 is a 170 degree one which fits, Hypertech makes a 160 and 180 degree thermostat etc...
 
I just learned that the issue could be the Oil Filter Gasket. Common issue on Mark VIIIs.

My 95 just went hot. I was losing Antifreeze also. I changed my thermostat and still over heated or at least got hot. Stopped before she got too hot.

Found out that 94m5 had the same problem on his 95. Told me tonight that his was his Oil Filter Gasket. He told me that presser can be lost by the failure of the gasket, also that it doesn't need to be leaking oil. This will cause air and loss of pressure with will either prevent flow and allow the antifreeze to boil.
 
98LSC32V said:
There are plenty of cooler thermostats. Napa Thermostat #3 is a 170 degree one which fits, Hypertech makes a 160 and 180 degree thermostat etc...
Click to expand...


I went to Napa and looked at a #3 thermostat. It is close, but it won't fit. The bottom plate is too small and it is too short. I still have had no luck finding a cooler thermostat. I've checked Ford, Napa, Carquest, Advance, Auto Zone, everywhere I can think of with no luck. Anybody who knows of a place to find a 170-180 degree t-stat for these cars (Gen 1 Mark VIII) let me know. I am still having a slight overheating issue. Not as bad as before, but it still gets up to the "R" quite often. Thanks.
 
well where is your fan turning on guage wise?
maybe your guage just reads higher than most
 
I have had the same problem for 2 years with my 93 mk8. I bought it that way, removed the T stat. That was at 164000 miles, i now have 217000 miles and still no t stat. just fill the overflow tank once a week. She still runs a 9.8 1/8 mile and gets 25 MPG
 
Call Eddie at 5 Star Ford on Monday... I got mine from him worked great. I got a lower temp one also....

By the way make sure you are putting the T-stat in the right way.... Just an Idea...

The one you took out might have been in up side down... Also the one in the shop manual is pictured up side down.
 
mespock said:
Call Eddie at 5 Star Ford on Monday... I got mine from him worked great. I got a lower temp one also....

By the way make sure you are putting the T-stat in the right way.... Just an Idea...

The one you took out might have been in up side down... Also the one in the shop manual is pictured up side down.
Click to expand...


Oops I mean Max sorry...
 
Funny thing...last summer I was overheating, so I had a new Tstat put in. This one ran to the "o" on the gauge but never higher. Mech told me it was a 280 degree Tstat or some such thing. Okay by me. But this summer, which is much hotter, the needle has barely reached the "M" and usually stays by the "A". Weird, huh.
 
Guess what! Gutted my third cat and the problem went away! Cat was apparently getting clogged causing the engine to run warmer and also making the engine sluggish. I've got more power and better gas mileage too! Cool! Now, even in 100 degree heat, the temp gauge stays around the middle of the normal range.
 
does it matter what year mark viii and about filling from the reservoir causing air in the system trouble? seems some fill from the overflow no problem others say don't do it. i had overheating trouble (1995 mark viii - 182K miles) with what i thought was a stuck thermostat - but before the thermostat was replaced ($288) i had the oil changed and antifreeze came back through the system and into the overflow. but on the way home overheated again like stuck thermostat.
 
ris4mis said:
does it matter what year mark viii and about filling from the reservoir causing air in the system trouble? seems some fill from the overflow no problem others say don't do it. i had overheating trouble (1995 mark viii - 182K miles) with what i thought was a stuck thermostat - but before the thermostat was replaced ($288) i had the oil changed and antifreeze came back through the system and into the overflow. but on the way home overheated again like stuck thermostat.
Click to expand...

Year does not matter....

I've heard that a bad oil filter adapter gasket can cause some issues also. Colleen runs through the adapter.

Was the T-sat put in correctly? A local shop put my friends T-stat in upside dow.

I also did this once shop manual shows the T-stat housing in a different direction than what you will be looking at under the car.
 
pull the plugs. smell holes,plugs,exhaust for antifreeze use a blue light to detect for leaks around the motor. these cars breath from bottom to do you still have the airdam .pressure testers work great to
 
Hi All! Its been awhile!
I had the same problem. When I installed my trans cooler I found that my radiator was full of fuzz and dust. Alot of cottonwood trees where I lived. Took a hose to it and no more problem. I could only see the fuzz and such after I removed the top radiator brace and leaned it back.
Good Luck
Raoul
 
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