I have a 1994 K3500 with over 200,000 miles on it. All stock, plan on updating many items after I figure out issue. It spits up coolant only when I drive at 65mph for over 15 minutes not under load. Does not overheat, runs fine. Took to shop to see if it was head gasket. One shop said yes (I think because I baited them but telling them my thoughts.) other shop said no. Did emission test on reservoir came back negative. Tested cap, needed new one. Replaced. Problem now back. The engine does have significant blow by. I watch oil so not a problem. I just don't have the space for full rebuild. Are there other things I should check before I commit to rebuilding engine. I am not using it to pull heavy loads, it is by daily driver and if I watch fluids it works fine. The body and interior is mint and I really want a reliable truck. I bought the truck pretty cheap, but want a piece of mind for road trips and putting some money into performance. It is hard to turn into a powerful truck if the heart is defective. Any tips would be greatly appreciated.
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Loosing coolant from radiator reservoir during not constantly.
- Thread starter Blue
- Start date
ak diesel driver
6.5 driver
I'd put a scanner on it and verify the dash temp gage is accurate.
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JayTheCPA
Well-Known Member
Blue, AK's comment was to verify that the dash gauge displayed what the ECM saw (inference is that the gauge might not indicate properly and the engine is actually running hot).
And by the way . . . :welcome2: to TTS! :hihi:
And by the way . . . :welcome2: to TTS! :hihi:
Sorry, I was confused with erg. What scanner would I need to accomplish this? They said they scanned it at shop and nothing came up. But they could be pulling my leg. If you want something done right you should do it yourself, thus my membership on this forum. Or a different way to check temp.
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NVW
Well-Known Member
http://www.leroydiesel.com/Page_2.html
GMTDScan at the bottom of the page. It will set timing and read sensors and more.
GMTDScan at the bottom of the page. It will set timing and read sensors and more.
jmiller
Recruit
If your loosing coolant, down to a specific level on a regular basis, start checking for a blown head gasket.
You can search many good posts here, but the quick check:
When cold, check the upper radiator hose. If any firmness is noted, open the reservoir cap to release the pressure.
With the cap installed, start the engine and check the upper radiator hose.
If the hose is rock hard within the first minute, you have a compression leak.
There are further checks to isolate which side if your interested in not pulling both sides.
I would see the low coolant light when I first started the truck. As it warmed up, the light went out.
What I found in my truck was a bubble building up behind the thermostat. This backs up coolant in the reservoir causing it to push out. After looking around the overflow hose, I could see remnants of coolant stains on the inner fender. Once it pushes out. the coolant level seemed to stay at a stable level. (So I ran it just below low)
You can search many good posts here, but the quick check:
When cold, check the upper radiator hose. If any firmness is noted, open the reservoir cap to release the pressure.
With the cap installed, start the engine and check the upper radiator hose.
If the hose is rock hard within the first minute, you have a compression leak.
There are further checks to isolate which side if your interested in not pulling both sides.
I would see the low coolant light when I first started the truck. As it warmed up, the light went out.
What I found in my truck was a bubble building up behind the thermostat. This backs up coolant in the reservoir causing it to push out. After looking around the overflow hose, I could see remnants of coolant stains on the inner fender. Once it pushes out. the coolant level seemed to stay at a stable level. (So I ran it just below low)
jmiller
Recruit
What i had was not a system fill belching issue. Its a continuous building of air from a compression leak.
You can cheap it by drilling a small, 1/16", hole in a t-stat.
This will bleed the air until it gets worse.
But you should understand IF a head gasket is leaking or not. The other thing would be a crack in the head. It is important to know which side leaks.
A visable crack may not leak. A leaking crack may pass a pressure test. ( been there, spent that money multiple times)
I've had a crack, I've blown gaskets, I've busted blocks.
In the morning, pop the hood. Make sure the upper hose is as squezy like a woman. Start the truck, stays squeazy while cold is good. Stiff as a dude when cold would be bad.
Hope its OK.
jmiller
Recruit
Examples
Blown head gasket, Caused by the sealing ring being damaged. Either from installation or shipping.
cracked head that "passed" a machine shop hot water bench pressure test.
These were part of a single repair event that took 4 head gaskets, 4 sets of TTY head bolts and a re manufactured head to replace the cracked #1 cylinder.
That finally stopped the coolant from puking from the reservoir. Then the carnage link in my sig happened later on.
Blown head gasket, Caused by the sealing ring being damaged. Either from installation or shipping.
cracked head that "passed" a machine shop hot water bench pressure test.
These were part of a single repair event that took 4 head gaskets, 4 sets of TTY head bolts and a re manufactured head to replace the cracked #1 cylinder.
That finally stopped the coolant from puking from the reservoir. Then the carnage link in my sig happened later on.
JMJNet
Recruit
There should be a bleeder valve before the t-stat.
Open it up till you see all the bubbles out and tighten it.
It is still squishy while cold. I am running at 180-190F. I have never seen it get over this temp even on recent hot days and running 70 on freeway. This is also not under load . Just city driving here in the twin cities.
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Will L.
Well-Known Member
You have two temperature sending units. One send signal to the ECM the other sends a signal to your Dash gauge. What he was talking about above is a possibility of one unit good and one unit that is bad.
To bleed it, i crack open the bleeder and start the cold engine. I let it warm up until the t stats open and it will spit out any air. Once the tstat is open and there is a steady stream of coolant coming out, tighten the bleeder and top off the reservoir.
I would bleed out the air, top off reservoir, then shut it off. Now break out the coolant system pressure tester and pump it up to 16-17 psi. Wait 1-1/2 beers or for us non drinkers one pb&j samich and a pepsi. If you have a loss in coolant that you can not find on the ground (my guess from a sneaky hose clamp or a cracked reservoir), pull ALL the glow plugs and crank engine by HAND to see if you have loss into a cylinder.
To bleed it, i crack open the bleeder and start the cold engine. I let it warm up until the t stats open and it will spit out any air. Once the tstat is open and there is a steady stream of coolant coming out, tighten the bleeder and top off the reservoir.
I would bleed out the air, top off reservoir, then shut it off. Now break out the coolant system pressure tester and pump it up to 16-17 psi. Wait 1-1/2 beers or for us non drinkers one pb&j samich and a pepsi. If you have a loss in coolant that you can not find on the ground (my guess from a sneaky hose clamp or a cracked reservoir), pull ALL the glow plugs and crank engine by HAND to see if you have loss into a cylinder.
jmiller
Recruit
This is a really good sign. The alternative can get expensive enough.
As Will L. mentions, start looking for leaks or the signs of leakage.
A small leak may not drip when cold, other than being moist. But may leak more when hot and evaporate. These tend to leave a bit of a trail or stain around the leaking area.
Depending on how good your eyes are, mine are not so good. In a darker area and a good strong flash light, check around the block, water pump, hoses and radiator for signs of coolant stains. ( I prefer my LED mag light - super bright)
It might be worth the time to pull the accessory mounting brackets to get a good look at the water pump and front cover. It can be tough to get a good look around the water pump
Check the thermostat mounting to the heads. Also around the blocking plates on the backside.
External leak areas I've seen or heard about.
around the hoses, loose clamps.
around the pump connection into the front cover and to the block
either the thermostat housing to head, and or rear blocking plates.
the side tanks seals leak, or the tank is old enough to start cracking. (possibly pull the radiator to inspect closely)
External block to head seeping
Freeze plug seeping
other leaky things
You'd probably smell a heater core leak, or seen foggy windows.
You don't have a Burb with rear heat.
On temps, once your confident the gauge is accurate.
I've seen two things.
Under load, temps spike to above 210. Carrying a snow plow at highway speeds can block air flow, causing temps to rise.
You can research Heavy Duty fan clutches, DMAX Fan blades, Electric fans, etc. I solved my issues by lowering the engagement temp for Fan lock up.
To save fuel, GM set the lock up temp pretty high. It seemed like between 215 and 220.
There are several good threads on changing this by modifying your stock clutch.
My experience was very good. With the plow blade on, fully raised, 40F to 50F day, running 60mph or better on the highway. This moved enough air to create a low pressure area between the grill and blade. Causing the temperature to rise. Only dropping the blade to just off the pavement would drop the temps.
Stock clutch would allow temps to get just above 215 before you heard the fan lock in. Once locked in, it would drop the temps, momentarily, below 200.
215 is just too hot for the heads.
I modified the sense spring and dropped the engagement 10 to 15 degrees. A quick spike from a hard run, can still get you above 210. But slow easy driving should allow the modified clutch to sense the temps and lock in early enough to keep temps in line. IIRCC, I lengthened the spring tab about 1/8". This kept my temps under 210. (except on a hard quick run) I would have done 3/16 or 5/32, on the tab, if I hadn't gone the wrong way and trimmed the tab. (OOPS) Take care to not get the lock in temp too low, it will impact MPG.
FYI, my fan clutch had well over 200k on it when it was modified.
DO NOT take my word.
Research, study, experiment on the cheap and easy (when you can), then observe your results. There is plenty of great experience here is this forum. You can confirm these experiences on other forums too.
Good Luck, these types of problems can be challenging.
Will L.
Well-Known Member
One other thing I forgot for coolant leak- a/c dye. Dump in a bottle- it won't hurt a thing. Then after running the engine for the air bleed it will be through out the system. Pull it in the garage and kill the lights and pull out the uv flashlight.or if its dark at night where your at check it out at night time.
JMJNet
Recruit
Actually do at any temp.
The bleeder is before the t-stat, so it does not matter whether the t-stat is open or not.
It only bleeds the air pre t-stat.
I know where I am loosing coolant. It is coming out of the radiator overflow. I bled the pre t stat, no issues for a few days. Just drove on freeway it spit up again. Bled again lots of air Any tips would be helpful. One thing I heard is because I may have a piston ring issue due to lots of blow by it is creating back pressure in the cooling system. Is there any truth to this? Any other tips? Will changing the cdr valve help?
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NVW
Well-Known Member
You either have a bad head gasket, cracked head or block. Blowby isn't the cause of coolant loss.