Overheating Mk48... looks like a radiator cap is needed too... help please.

[Augdog1964]

Hey all,

Well had the Mk48 out and while we were putting the Mk15a1 trailer through its paces, the radiator began leaking copious amounts of juice from around the cap.

Took the cap off today, and basically the seal is shot... anybody know where to find:
NSN: 5342-01-466-9758 45152 1461820 CAP, RADIATOR

Also to you other Mk48 owners... do your units run hot? Mine seems to constantly run 220+ which is almost pegged at the 240 degree max on the gauge...

Any ideas? She's full of juice and once I get the cap fixed that may help too... certainly will stop the geyser at the cap.

Thanks in advance!

 

[sandcobra164]

The radiator cap should be an easy fix. You've already found it. As to the high temps. We've got to get used to that. The EPA long ago told the Military that those trucks will burn cleaner if everything is hotter. I dislike that statement. My deuce was smoking out the stack at idle earlier today but that's probably because he was running for "free". He's on a new diet that makes his IP last alot longer. Take the Sulfur out of Diesel, we'll find a way to put it back in. The EPA target's the Military and they're trucks, we end up with them and get them ready to run up and down the road with them. For what it's worth, make sure you have good turbo seals on that truck. Diesels love oil and Detroits love it even more. If they get a good supply, they will "run away".

 

[Hoefler]

My Mk runs gauge hot with recorded temps just like yours. My cap and radiator has not leaked or steamed. Have read about operating temps in these engines and have learned they don't like temps over 200 degrees. Apparently they have o-rings as head gaskets that get brittle with temp.
I decided to take the doghouse cover off (inside of cab), and measure temp right at the electrical sensor on front of engine. When my gauge reads 210 or so, the infrared measured temp was actually 185. When pulling up hill with decent throttle applied, she would rise to about 193 or so- with gauge over 220. I measured all over the engine and found no areas over these temps.
What I learned- seems water temp sensor or guage is not accurate. I also learned that no matter how cow bell is applied, when running with doghouse cover off-its loud enough to drown out the sound of hundreds of cowbells. Lastly- running without doghouse cover is pretty neat when driving- it's sort of a madman deal with lots of parts rotating right next to your right arm! Really cool.
In summary, I have bought a mechanical guage from jegs. Am putting a pipe tee in and connecting both the sensor and mechanical sensor in the tee. I need some assurance of my engine temp.
hope this long winded write helps.
pete

 

[bbf]

there are 2 temp sensor and i had to replace both my gauge was reading over 220 as well

 

[Augdog1964]

bbf,

Where did you find those temp sensors, and where did they go?

Hoefler,

Thanks for that info! I appreciate it!

 

[Augdog1964]

The radiator cap should be an easy fix. You've already found it. As to the high temps. We've got to get used to that. The EPA long ago told the Military that those trucks will burn cleaner if everything is hotter. I dislike that statement. My deuce was smoking out the stack at idle earlier today but that's probably because he was running for "free". He's on a new diet that makes his IP last alot longer. Take the Sulfur out of Diesel, we'll find a way to put it back in. The EPA target's the Military and they're trucks, we end up with them and get them ready to run up and down the road with them. For what it's worth, make sure you have good turbo seals on that truck. Diesels love oil and Detroits love it even more. If they get a good supply, they will "run away".

sandcobra...

Is there any way we could get some photos of an in service Mk48/15a1?
We owners are trying to find out what goes in the external stowage locations, as well as the internal ones.

Thanks!

 

[RDUKW]

sandcobra...

Is there any way we could get some photos of an in service Mk48/15a1?
We owners are trying to find out what goes in the external stowage locations, as well as the internal ones.

Thanks!

The TM's have a list of every part and which compartment it goes in. Mine and all the others I have driven run about the same temp with the high end being up around 220. I will keep my eyes open for a cap.

 

[123mack]

In regards to the sulfur, how did you "put it back in"?

 

[bbf]

from a oshkosh dealer in ill
had to replace the rad cap pickup at a truck supply i think it was a 7p to 11 p

 

[Augdog1964]

The TM's have a list of every part and which compartment it goes in. Mine and all the others I have driven run about the same temp with the high end being up around 220. I will keep my eyes open for a cap.

I have the two TMs that I know of... and can't find anything on it...
is there another TM about the 15a1?

 

[Augdog1964]

Found it... always check the Appendix!

Pg. 878-881

 

[Augdog1964]

Guys,

Any contacts for Oshkosh parts? I still can't find anyone I can get the Radiator Cap, chain, and attaching hardware...
My Mk48/15a1 is down for the count w/o the cap!

Thanks!

 

[Hoefler]

Try here-http://radiatorgroup.com/tractorradiatorcaps.aspx
Looks like they have a larger cap.
Pete

 

[sandcobra164]

Dave,
Please PM me an address, I'll get one shipped your way on Friday. It won't have the chain or attaching hardware as they re used those pieces when they replace the cap.

Joseph

 

[BrushMaster Builder]

The radiator cap should be an easy fix. You've already found it. As to the high temps. We've got to get used to that. The EPA long ago told the Military that those trucks will burn cleaner if everything is hotter. I dislike that statement. My deuce was smoking out the stack at idle earlier today but that's probably because he was running for "free". He's on a new diet that makes his IP last alot longer. Take the Sulfur out of Diesel, we'll find a way to put it back in. The EPA target's the Military and they're trucks, we end up with them and get them ready to run up and down the road with them. For what it's worth, make sure you have good turbo seals on that truck. Diesels love oil and Detroits love it even more. If they get a good supply, they will "run away".

Gentlemen, want to clear up a couple of the statements made. One, the military and DOD never sacraficed higher operating temperatures to appease the EPA. As a matter of fact, the DOD is still running EPA Tier II/III Engines in new production versus the current EPA Tier IV standard which all commericial fleets and OEMs nationwide must ahhere to. Also, an ex-Oshkosh guy, Detroit mechanic, and Warrant officer, I can tell you the 8V92TA in your MK and HEMMT trucks is designed to run between 182 and 190 degrees all the time. DO NOT run your engine over 210 degrees. You will cause damage........These trucks and engines were put thru testing at the National Automotive Test Center under what is called a 3/10th Tractive Effort Full Load Cooling Test. Which, in laymans terms means the cooling system was tested by placing a sled of 10k or greater behinh the truck, loading it with it's prescribed cargo weight, the placing the transmission in 1st and the transfer in low. The test technician then proceeds to "floor" the truck and run it around the track pulling the cargo weight and sled under these parameters. They do this for 4-6 hours or until they get the best consistent measurements of the cooling system and the transmission sump temperatures.
What you may be thinking concerning high temperature requirements are newer TIER IV EPA engines with EGR and Selective Catalys Reduction (SCR) which require higher combustion and operating temperatures to "clean up the exhaust emissions".

 

[Hoefler]

I have found the gauge in my truck does not read accurately. My truck shows operating temps of 220F. After much reading on these engines, I had determined that running my MK at this temp would surely destroy the O-rings at head-block.
I removed the dog house cover in cab and shot an infrared temp device at the temp sensors on the front of the engine. I did find my engine runs at 180 to 190 degrees F. A more accurate mechanical gauge will be added to my truck over the winter time.
Pete