Community Forums

Clay L · 05-06-2009, 04:12 PM

Re the 8.1L engine:

I have done a search and read some good info on this but I have a question.
Driver said in one post that the engine drain plug is on the the drivers side of the engine. I see two brass plugs there. One is a 17 mm recessed hex head and one is much smaller - a 8 mm hex head. Which one is the drain?

Also how do you drain the coolant from the MotorAid system?
The pipes and hoses going back to the water heater and the rear heater run along the frame and it would seem that they may not drain.

edgray · 05-06-2009, 04:26 PM

CLAY: Rather than trying to "drain" your system, I suggest you FLUSH the entire system. Visit OEMY's website for a very easy method that will (should) clean out all the old coolant. ED

scoutmstr · 05-06-2009, 06:38 PM

I still like to remove both drain plugs in the engine. 17MM on each side as well as the radiator drain plug. It's messier than OEMY's way but then I'm not concerned with the thermostat diverting the flow of water which may happen with power flushing. BTW I've being doing it for 30 yrs on the same '78 IHC and never had to replace a drain seal. MEant to say drain plug

Clay L · 05-07-2009, 07:34 AM

Quote:

Originally Posted by scoutmstr

I still like to remove both drain plugs in the engine. 17MM on each side as well as the radiator drain plug. It's messier than OEMY's way but then I'm not concerned with the thermostat diverting the flow of water which may happen with power flushing. BTW I've being doing it for 30 yrs on the same '78 IHC and never had to replace a drain seal. MEant to say drain plug

I don't see the one on the passenger side. Can you describe where it is?

DriVer · 05-07-2009, 10:01 AM

Quote:

Originally Posted by Clay L

I don't see the one on the passenger side. Can you describe where it is?

Clay, I believe we have a sensor on one side and a plug on the other.

scoutmstr · 05-07-2009, 02:34 PM

I went under the MH since I didn't remember exactly. Found one drain plug on each side about 3/4 way back both look the same. Measured them at 18MM not 17. I believe they are the coolant drain and not oil plugs. Checked the manual Supplementw8101007 which deals with the 8.1 engine. Section6-176 #20 says "Install the engine block coolant drain hole plugs" It is pural and I think I remember two. Clay, if you do this and find out that I remembered wrong let me know these arent the coolant plugs so I dont take them out next time

Clay L · 05-09-2009, 08:13 AM

Quote:

Originally Posted by scoutmstr

I went under the MH since I didn't remember exactly. Found one drain plug on each side about 3/4 way back both look the same. Measured them at 18MM not 17. I believe they are the coolant drain and not oil plugs. Checked the manual Supplementw8101007 which deals with the 8.1 engine. Section6-176 #20 says "Install the engine block coolant drain hole plugs" It is pural and I think I remember two. Clay, if you do this and find out that I remembered wrong let me know these arent the coolant plugs so I dont take them out next time

I found an 8mm plug on the passenger side of the engine. It's an 8mm recessed hex and is about the same distance back as the 8mm on the drivers side.

I drained the radiator yesterday and will drain the engine today.
I am going to remove the two 8mm plugs and the 17mm one also just to see what is behind it. I did insert the 17 mm hex and it fits tightly so my engine (2003) must be different than yours in that regard.

DriVer · 05-09-2009, 08:23 AM

Quote:

Originally Posted by Clay L

I am going to remove the two 8mm plugs and the 17mm one also just to see what is behind it.

Clay, Unless you remove the 3 coolant jacket plugs simultaneously, (if that's what they are) I'm not sure that you'll get more out of the block.

I would say that once the T-Stat is pulled and one block plug removed, whatever coolant is in the block will most likely drain down from that open plug.

Having 3 plugs ... would 6 be any better? I'm just wondering?

Just note that when we have seen very slow leaks the source was the driver's side plug being loose.

Waiting to hear how all of that worked out today .... good luck with your project.

Clay L · 05-09-2009, 02:23 PM

Okay it's all done.
Removed the two 8mm plugs and got a total of 5 1/2 gallons out of them and the radiator. I got a little over a gallon from one, replaced the plug and got the same from the other side.
It looked great - clear pink and no rust - but I am sure the additives were at the end of life.

I did not remove the 17mm plug since I got out what I understand to be the right amount of coolant.

I did have to remove the bolt holding the air intake horn so I could get a grip on the radiator cap. As mentioned by Max in an earlier post that sucker is a bear to get off.

Many thanks to Max Hubrich for the tip on how to open the radiator drain plug with a 1/4 inch extension and ratchet.

Ron & Dee · 05-10-2009, 09:54 AM

Quote:

Originally Posted by Clay L

Okay it's all done.

I did have to remove the bolt holding the air intake horn so I could get a grip on the radiator cap. As mentioned by Max in an earlier post that sucker is a bear to get off.

Many thanks to Max Hubrich for the tip on how to open the radiator drain plug with a 1/4 inch extension and ratchet.

That radiator cap is a boogger to remove. I had to do the same thing but even at that, being short like me, it was hard to get any downward force to open the cap

Let me know how your operating conditions, tempertature, are after your complete job.

Thanks,

Ron

DriVer · 05-10-2009, 01:57 PM

Quote:

Originally Posted by Ron & Dee

Let me know how your operating conditions, temperature, are after your complete job.

Ron, Unless Clay has a Scan Gauge or direct reading temp gauge this might be difficult. Normal runs from 190° to 240° F. Temperatures of 247° and up should be suspect of an overheat condition.

Ron & Dee · 05-10-2009, 02:25 PM

Quote:

Originally Posted by DriVer

Ron, Unless Clay has a Scan Gauge or direct reading temp gauge this might be difficult. Normal runs from 190° to 240° F. Temperatures of 247° and up should be suspect of an overheat condition.

Mike,

Even though there is quit a spread of normal temperature, I would like mine to run closer to the 190 than upwards toward the 140, especially in the desert and mountains.

Ron

scoutmstr · 05-10-2009, 04:48 PM

Quote:

Originally Posted by Clay L

Okay it's all done.
Removed the two 8mm plugs and got a total of 5 1/2 gallons out of them and the radiator. I got a little over a gallon from one, replaced the plug and got the same from the other side.
It looked great - clear pink and no rust - but I am sure the additives were at the end of life.

I did not remove the 17mm plug since I got out what I understand to be the right amount of coolant.

I did have to remove the bolt holding the air intake horn so I could get a grip on the radiator cap. As mentioned by Max in an earlier post that sucker is a bear to get off.

Many thanks to Max Hubrich for the tip on how to open the radiator drain plug with a 1/4 inch extension and ratchet.

Clay,

Where front to back is the 8mm hex head on the right side? Obviously I remembered wrong?

DriVer · 05-10-2009, 05:02 PM

Quote:

Originally Posted by Ron & Dee

I would like mine to run closer to the 190 than upward toward the 240, especially in the desert and mountains.

Ron, The 8.1L engine is an internal combustion engine and as such it relies on heat to do its job. That's what it does best is make heat. Getting the cool pack to shed excess heat within or above the threshold of normal is what the cooling system does and it will do that if all is mechanically sound.

I ran a few mountains in the past 77,000 miles that I have clocked over and knowing exactly what the "actual" temperature was nice to know however it was never critical to the point where I obsessed about keeping the operational temperatures under 200. If driving route 95 out of Needles, CA to Vegas in July counts as desert driving then I didn't have any problem there either. The biggest problem there was keeping the occupants cool however the engine was happy as a pig in mud! :}

Expecting that temperatures will not exceed 218-220 degrees while under a severe load is impractical. When the fan clutch kicks in and you can see the MPH increase while the temperature goes in the opposite direction -- all is well in Mudville!

I am going to recommend that unless there is something that compels your concern about your cooling system and that if there is any doubt have the situation evaluated by a service center.

Be aware of the cooling systems requirements however excessive concern I believe is unwarranted. Go on your trip and have a good time.