1986 345 AS MH Engine Temperature

Jim Tyrney · 03-29-2004, 10:07 PM

In the 1986 345 owners manual, it says that the normal operating temperature is 190 deg. to 240 deg. I hope to be making a trip to Oregon in June and will have to go thru some pretty good climbs between here and there. I am running per the original temperature guage approx. 205 deg. under normal mountain roads here in Louisiana and I know SOME of the mountain roads going to Oregon are a little higher. Is this about the normal temperature that 345's run? Any suggestions if this is not normal? Thanks for any replies. Jim

swebster · 03-29-2004, 11:48 PM

Jim,
They do tend to run "hot". Mine runs at 180 and hits 200 on a long climb, but I did a complete radiator out cooling system flush last summer she was hitting 220 + and the temp light came on during a climb in the Smokies. My P30 manual say it runs a 195 to get the most efficiency from the engine.

I think 240 is too high. You should try a radiator flush before your trip to remove scale and deposits in the system. Then if your travelling in the summer you might want to add something called "water wetter" (CRC brand is "Tow Kool" from Pep Boys) which can lower your temp about 20 degrees.

Make sure you check your hoses and don't forget the heater hoses up front and the ones running to your aux heater under the couch (especially where the pass through the floor) and back to your water heater.

87MH · 03-30-2004, 06:19 AM

My '87 345 runs 210 at idle, but I have never seen it above 220 in Louisianna mountains, East Texas Mountains, or even the Rocky Mountains.

I do intend to change out the thermostat the next time I haver access to the front of the engine.

ALANSD · 03-30-2004, 07:26 AM

I used that same CRC stuff Steven imentioned...with a correct mix of distilled water and anti-freeze I got 180-190 max temps in 98 degree weather pulling my Saturn behind us. I did a flush before using one of those prestone flush kits on the heater hose. And my heater core is bypassed which should probably have increased the temps, but didn't seem to change them much. Its been out for almost a year now.

Jim Tyrney · 03-30-2004, 08:41 PM

I also thought that the normal operating temperature in the owners manual on the top end of 240 deg. was a little on the high side. Steven, did you take your radiator out completely? Do y'all know what thermostat was originally installed? I'm not sure if it has ever been changed by a PO. Did y'all do the flush or did a radiator shop do it? I will surely look into getting "Tow Cool" added to the cooling system to get that kind of temp. drop. I will be checking the hoses for sure in the very near future and did I remember in a post that someone had the hose bust under the couch? I tell you, some of these MOUNTAINS here in Louisiana are a real challenge. Hope to hear more and thanks. Jim

swebster · 03-30-2004, 08:51 PM

Jim,
I did the prestone kit just like Alan. I did pull the radiator but that was becuase I was replacing the water pump and all of the belts so this made it easier.

I was the guy with the hose busting under the couch - not fun!

Cooling system maintenance is one of those "never thought about until it's too late" system but a little preventative care can make the difference between a great trip and a breakdown on the side of the interstate.

Jim Tyrney · 03-30-2004, 09:00 PM

Thanks Steven for the clarification. I will definitely do the flush and "Tow Cool". I'm really impressed by the amount of temp. drop with this additive.

ALANSD · 03-31-2004, 06:32 AM

mountains in Louisiana?

Jim Tyrney · 03-31-2004, 08:12 PM

When you get above New Orleans (below sea level as long as the levies hold), it's like being in the mountains. Jim

IPM · 04-02-2004, 06:38 PM

I managed to reduce the operating temp on my 28 ft unit a great deal.
First I replace the water pump, hoses, installed 180 thermostat, removed radiator and had it cleaned out.
Next I replaced and moved the engine oil cooler away from the radiator to the passenger side of the grill.
I added an oil cooler for the transmission.
I added an electric fan to cool the engine oil cooler and trans cooler.
I replaced the stock cast manifolds (huge heat sinks) with headman headers from summit racing (best price). Man did that get the heat away from and off the engine and put the exhaust heat under the chasis.
Temperature stays much cooler. Well under 180 when lightly loaded and I forget to turn the elecric fan off. I have to push it really hard to get temp above 200.

RichardT · 04-02-2004, 09:13 PM

"Temperature stays much cooler. Well under 180 when lightly loaded and I forget to turn the elecric fan off. I have to push it really hard to get temp above 200"

You want to have Engine oil temp of 180 or higher to get rid of condensation in oil so if you are running well under 180, that is actually not a good thing.

cooperhawk · 04-03-2004, 05:23 AM

IPM, what manufacturer electric fan did you install and did you make brackets for fastening or did you use the plastic fasteners that extend through the radiators for securing the fan?

moisheh · 04-03-2004, 08:34 AM

IPM; Why did you choose Hedman's over the others? I know they are priced better but when I put them on a Dodge chassis I found the flanges to be thin and the tubing of poor quality. They are made in Mexico. Does Hedman list a set specifically for the P 30? I agree with you about the exhaust manifolds. When I installed headers and a free flow exhaust all my overheating problems disappeared. BTW: Rather than buying the overpriced noisy aftermarket mufflers I used a long 3 inch in n out school bus muffler. I read about this muffler in trailer life about 15 years ago. They had a tech editor who had a dyno shop in Calif. (forgot his name). He tested this muffler and found it to have minimal back pressure. Was also fairly quiet. If any one is interested I will try and find the part #.

dinoburb · 04-03-2004, 10:18 PM

Hi Folks,

As some of you know I'm partial to Thorley headers, however, Hedman does make a heavy duty header with 3/8" flange and 14ga tubes which is the same spec as Thorley's TriY Header. The Hedman header even has a heat resistant coating and they are about $100 less expensive. The primary difference, other than price, is the Thorley's are designed for increased torque in the low and mid range. That area is where we operate. Hedman and others of that genre tend to aim for increased HP in the higher RPM ranges. Both designs, however are a significant improvement over the stock cast iron anchor headers!

Hope the info is of some value.

Take care,