98 K3500 Cooling/Head Question

[CedarGrove]

So I bought a 98 K3500 Crew Cab the other month and I am paranoid that I've got a cracked head. Here's why:

1) I think the exhaust smells a little sweet, but this is the first diesel I've owned with a cat convertor so maybe that's why it doesn't smell the way I would expect it to smell.

2) I seem to lose about a half a gallon of coolant a week. I top it off on Sunday and the low coolant light comes on intermittently on Thursday or so. I've never let it get to the point where it stays on constantly. Maybe it's just the sensor.

3) ECT seems a bit erratic to me. My 84 6.2 stays steady at about 180 all of the time. This truck likes to fluctuate from 180 to 210. Maybe this is normal. Maybe the thermostats are wacky. Mechanic replaced them when I first bought the truck.

4) Blew a water pump 2 weeks ago.

5) My heat in the cab can be erratic. Starts hot, then cools down, then warms up. Maybe the heater core needs to be cleaned out.

These are all small things but I think they point to a head problem. I have a good (I think) diesel mechanic and he doesn't seem too worried about it. He has tested the coolant for combustion gasses and the test was negative. He replaced a warped exhaust manifold on the turbo side when I first bought it. There is no indication of water in the oil.

I put a radiator flush in when I changed the water pump. I flushed that out last week and I am running straight water at the moment. I'll drain that in the next week or so and add coolant. Previous owner was running the green stuff. The mechanic has agreed to retest this week for combustion gasses in the coolant. In the meantime, I am going to replace the low coolant sensor and back flush the heater core.

Anything I'm missing/need to take a closer look at?

Cheers!

98 K3500 CC DRW 6.5 TD
84 C10 J code intake
83 C10 w/veggie conversion

[a5150nut]

Did you bleed the air out of the cooling system?

[CedarGrove]

Through the bleeder on top? Yes.

[TAG]

I have seen several posts in here that the combustion gas testers do not work on diesels, only gas engines.

[Scooby]

Combustion gas testers should work on both gas and diesel. The one I have definately works on diesels. I have not used it on gas, but I think they detect CO2, but I am not sure

[CedarGrove]

The temperture spiked a couple of times yesterday while driving around. Once while towing a small trailer, once without. Dropped it at the mechanics place and he doesn't really know which direction to go. Previous owner replaced the radiator and it seems good. I did notice one thing when it started to heat up...I turned on the heater and as the temp guage was rising to just below the red mark, there was little heat coming from the blower. After about a minute, the guage started going back to normal and the blower started kicking out good hot air again.

Quick poll...Who here thinks it's probably a cracked head? I need a direction to go. I know my mechanic doesn't want to get in to the heads, but I feel like that's where it's at.

Should I take the coolant crossover pipe off and disconnect the serp belt and look for bubbles? Mechanic says those bubbles would show in the combustion gas test which has already shown negative twice.

Throw me some ideas.

[93GMCSierra]

could be cracked head, or just gasket, though with no bubbles in the coolant I would think maybe it is something else, maybe in the heater core?

[JohnC]

The behavior with the temp gauge and heater implies there is air in the system. Did you bleed it again? If the head or head gasket is bad, it'll keep getting air in it. Also, the water pump and radiator issues could be due to excess pressure. Have you tested and/or replaced the pressure cap? Does the radiator hose get rock hard shortly after starting cold?

[CedarGrove]

I agree about the air in the system. I replaced the cap when I did the water pump. The upper hose does not get rock hard when I first start it.

Is there a sniffer that will detect coolant in the exhaust?

[befland]

Cedar Grove,
I only live about 4 miles from your town (Efland). Who is your diesel mechanic?

Bill

[CedarGrove]

Nice to hear from you Bill. I've been working with Fred Cooper on Walnut Grove Church Road. He is a Ryder fleet mechanic. Very competent and reasonable mechanic and all around good dude as far as I can tell.

I ordered heads/gaskets and the like last week. Fred has agreed to supervise me on the tear down and replacement so I'll take the truck to his place and work on it there. I'm going to try to do as much as I can myself and he'll be nearby to give advice and whatnot. I'm looking forward to it.

So I ordered heads, gaskets, new tty bolts, marine injectors (since I'm right there), 4" exhaust. I also had on hand some guages that I'll be installing during this process.

Looking forward to being on the other side of this project.

Come on over one evening and take a peekaloo.

Cheers,

Lewis

[befland]

Lewis,
I did the gasket install on mine shortly after I bought it. It had 90K on it when I bought it and I did the head gaskets at about 120K-130K. Since I had the earlier 6.2 (1983) I whent ahead and sleeved the coolant passages like on the original dieselpage project truck. I'm in the process of replacing the engine and hope to re-install this weekend (broke the crank at 367K miles). I have a lot of parts if you need them...all kinds of gaskets etc. I'll try and catch up with you over the next couple of days. Send me a PM (my email id is in my signature) and I'll give you my cell #.

[CedarGrove]

Got the passenger side head off tonight. Cracked between valves on the cylinder closest to firewall with signs of coolant leaking.