Question about Hino 338

TruckAllOver

Seasoned Expediter
Hi, I have been reading this thread about Hino trucks in search for a solution to a engine problem I'm experiencing with a 2008 Hino 338.
I'm directing the inquiry to greasytshirt.
The low coolant alarm will sound when two things occur, drive for at least 50 miles at normal highway speeds, make a turn to the right, like going on an interstate off ramp that makes a 180 degree turn on to secondary road. The alarm will come On during the turn and then go Off when the truck is no longer in the turn. Engine temperature has remained normal and there has not been any over heating issues.
I have replaced the alarm sensor and radiator cap, cleaned the radiator and tranny cooler fins of any debris and the problem still occurs.
In an effort to continue looking for a solution to the alarm problem, I tried doing the following.

I topped off the radiator by pulling coolant from the coolant reservoir till the radiator was completely full.
I placed a mark on the coolant reservoir tank at the level of the coolant after topping off the radiator. This is what I have observed about the alarm and coolant level. If I drive short distances, 5,10,15,25,40 miles the coolant level comes back to the mark I placed on the reservoir tank after the engine cools completely.
If I drive a greater distance like 50 miles and up the alarm will sound on the right turn as described above, and the coolant reservoir is about an inch or slightly more after the engine is completely cool.
Ultimately I believe this alarm problem is a hint to a bigger problem developing , do you know what that might be? Thanks for any help you can provide.
 

greasytshirt

Moderator
Staff member
Mechanic
How much coolant do you add per day? Week?

If that sensor gets uncovered, the alarm will sound. If gases enter the cooling system, this can happen.

I would look for leaks. Common places include the oil cooler and head gasket. Left rear corner, or behind turbo, especially.

Also have a combustion gas test performed on the cooling system . If the head gasket or an injector cup begins to leak, it will push a high amount of CO2 into the cooling system. This test detects CO2.



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TruckAllOver

Seasoned Expediter
Not having to add coolant to reservoir. Standing in front of truck looking at engine there seems to be a coolant stain on right rear side of engine fire wall, but do not see anything else. Will get inspection mirror out and see if I can spot some sort of leakage around turbo.
Will look at having combustion test done. Anyone you recommend.
Thanks for the quick response.
 

floridawheels

Active Expediter
I don't get to help Mr. Greasy T often but... This is a do it yourself combustion gas test kit.

It's the one I got and Mr. Greasy said it was perfect for the test. Some of them require an air compressor or other outside tools/stuff, this one does not and is completely self contained.

Combustion Gas Leak Tester Detector Auto Tools Head Gasket Cylinder Engine Block | eBay

I'll not post what he called it... LOL.. (inside joke for Mr. Greasy)
 
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Tobster317

Expert Expediter
Owner/Operator
TruckAllOver:

It doesn't leak around the Turbo. It's behind it and towards the rear of the block. The rag is where the turbo exhaust is. The green circle is the back of the block where it leaks.
 

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greasytshirt

Moderator
Staff member
Mechanic
If I drive a greater distance like 50 miles and up the alarm will sound on the right turn as described above, and the coolant reservoir is about an inch or slightly more after the engine is completely cool.

I re-read your post. The level in the reservoir rises to a point greater than before and stays there, is that correct?

If yes, you have a leak. The leak is small enough not to actively drip, but large enough to allow air to enter the cooling system when the engine is cooling off. The reservoir fills but can't get sucked back into the engine. Think of a straw with a hole in it.

If you see coolant in the right rear corner, you probably need a head gasket. Re-seal the oil cooler at the same time because it's a frequent leaker too.

There are a list of parts that are not reused if they are removed. It's important that these are replaced if the head comes off.


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TruckAllOver

Seasoned Expediter
("I re-read your post. The level in the reservoir rises to a point greater than before and stays there, is that correct?

If yes, you have a leak. The leak is small enough not to actively drip, but large enough to allow air to enter the cooling system when the engine is cooling off. The reservoir fills but can't get sucked back into the engine. Think of a straw with a hole in it.

If you see coolant in the right rear corner, you probably need a head gasket. Re-seal the oil cooler at the same time because it's a frequent leaker too.")


About the reservoir level. I had a trip that was a couple hundred miles and sure enough as soon as I started a right turn the low coolant alarm started up and as soon as I was driving straight again it stopped. So, before I turned the engine off for the day I removed the radiator cap (engine running) and the coolant was down maybe an inch or so, certainly not what I would call low. The next morning I opened up the hood and the coolant was pulled back down to the normal line I have marked on the reservoir. Wierd because normally the coolant would be at a higher level than before. Only thing I did different was checking the radiator when the engine was running and hot.

I will get a picture posted at what I'm looking at on the right rear firewall so you might decide if it is a coolant leak.
Big thanks for your help!
 

greasytshirt

Moderator
Staff member
Mechanic
If the level in the radiator is down an inch, it is low and it will set off the alarm.

Make sure the pickup tube on the reservoir cap exists. This sometimes falls off and into the tank. Also make sure the hoses aren't reversed on the cap.

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TruckAllOver

Seasoned Expediter
Thanks so much for your help as I work through this coolant problem.
Have been doing short runs lately and have had no alarm problems, but today I did a long run (75 miles) today and as usual the alarm started to singing out on the right hand turns. At my drop while they unloaded I let the engine idle and I pulled the radiator cap and put the coolant back into the radiator from the reservoir till the radiator was topped off. Then I shut the engine down while I took care of paper work. While inside I mentioned the problem that I have been having with the coolant alarm and the guy said maybe it is my clutch fan for the radiator. Anyway only about ten minutes passed before I was back out and in the truck with the engine running and I thought I would do a quick internet search about the fan clutch. The thing I found said that with engine at normal operating temperature and shut off the fan should be stiff to turn. So I turned off the engine and popped the hood and gave the fan a spin. It freely spun with no resistance.
Should that have happened? Is the clutch fan bad?
Oh yeah, I'm still working on posting the picture on the engine fire wall, I'm not as tech savvy as I thought. I'll post it soon. Thanks for listening.
 

greasytshirt

Moderator
Staff member
Mechanic
Do you hear the fan clutch engage at all? It will roar. When it's not engaged, it will spin freely.

This is probably unrelated to your coolant level issue.

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TruckAllOver

Seasoned Expediter
Just finished a load that was 15 miles local driving at 25 to 50 mph speeds. Heard the fan roar a little as you said. At my drop I turned off engine and tried to spin fan and it had resistance, a hard pull on fan blade and it might have turn a quarter turn before stopping, not the free spinning like yesterday where the same pull had the fan spin ten turns before stopping. Coolant was normal and no alarm.
 

TruckAllOver

Seasoned Expediter
The photo is of the area on fire wall right side on engine. It may be nothing. I noticed the stain about two months ago and there has been no change as to how the stain looks today.
 

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greasytshirt

Moderator
Staff member
Mechanic
That is in an area that does not have common leak sources. I'm assuming that's road salt.

The passenger side of the engine is where the action is. External head gasket leaks and oil cooler leaks are both common.

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TruckAllOver

Seasoned Expediter
Going to get that Co2 check done next based on your last post. Drove today 4 hours from Atlanta Ga to Knoxville TN and decided to keep the speed low at 53 on the cruise. Way to slow for I-75 but the coolant alarm did not go off when I reached the drop. Coolant was a little high in reservoir but obviously not so much that the alarm would go off. Staying overnight here at drop and will check all the hose connections again before heading back tomorrow.
Thanks again for your help!
 

cliffkujala

Rookie Expediter
I've experienced the same symptoms. greasytshirt is on the right path. You need to replace headgasket (or oil cooler). For me it was head gasket. My system would always fail tests for combustion in the coolant so I chased all types of possibilities before deciding to do head gasket but that is what finally fixed it.


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Tobster317

Expert Expediter
Owner/Operator
Truckallover. Have you done an oil analysis? You should do one, they are cheap, you can get it at Napa. It will give you the news you need and then some. I do one every 50K.
 

greasytshirt

Moderator
Staff member
Mechanic
I've experienced the same symptoms. greasytshirt is on the right path. You need to replace headgasket (or oil cooler). For me it was head gasket. My system would always fail tests for combustion in the coolant so I chased all types of possibilities before deciding to do head gasket but that is what finally fixed it.


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I'd just like to add that the oil cooler is accessible with the head off, and it's a perfect time to reseal the oil cooler.

If one is going through the time and expense of replacing the head gasket, I'd have all of the injector cups replaced too.

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TruckAllOver

Seasoned Expediter
I did the combustion gas test and no color change on the test fluid. The oil is fine with no discoloration. I did replace two hose clamps. One that is a spring clamp on a short hose that is running to some sort of heat exchanger on front of engine, top portion, turbo side. And another clamp that was corroded on the bottom of clamp like leaking has been occurring. That clamp was on the big hose that runs to bottom of radiator, the clamp I replaced was the top one coming from engine. I spotted the heavy corrosion with the inspection mirror.
Hey CliffKaJala you say you didn't have a positive test on the coolant for combustion gases so you just replaced the head gasket. So where was the leak on the gasket and how much did you spend to get it done....and how many miles on engine since you replaced the head gasket? Thanks. Oh and one more thing CliffKaJala, how long did you have the coolant alarm problem before you had the head gasket replace. Thanks again, y'all are a big help. And if anyone else has had a hino engine head gasket replaced I would like hear about your costs and dealer/mechanic experience. TY.
 
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