Coolant bubbling on 6.2 diesel

[meowmeow]

Hey all,

When I start my truck I noticed the coolant begins to bubble within ~60-90 seconds of the truck turning on.

Video: https://imgur.com/a/CPEyEPm

The coolant isn't hot at all at this point. I have a Chilton manual and looked through it but didn't find any info on bleeding air from the coolant. Most of my mechanical experience is with newer foreign cars so I wasn't sure of what the procedure is that I should be following to bleed it?

I'm worried it could be the head gasket but want to eliminate other possibilities first.

Thanks.

 

[SirRobyn0]

I'm more of a gas engine guy so someone with more specific experience with the 6.2 will probably come along with more specific information pertaining to your specific engine.

Assuming that your cap holds pressure, that would mean after 60 - 90 seconds of running it has built pressure though the system and is pushing air out into the reservoir. Just biased on that I'd say blown head gasket is very likely, actually I'd say there really isn't any other possibility other than maybe a crack in a head, I have no idea how common cracks are on the 6.2.

Hear is some diagnostic information if you'd like to further test it:

You can do a test called a block test, which the kit costs about $30 - $40 it is color change fluid that is held in a capsule and you put that on where the radiator cap goes with the engine running. The fluid is blue and will change to yellow if there is hydrocarbons i.e. exhaust gas in the radiator. If it turn yellow you have bad head gasket or crack in the block, if it doesn't change color you probably don't.

There are other things you can do without the kit though. Have you done recent work on the cooling system? if yes it might be trapped air, if no the it's unlikely given what I've seen in the video. Does the coolant smell like exhaust or diesel fuel? if yes it's likely a head gasket. Does the truck overheat? or did this start after a recent overheating? If yes just compounds the likely hood.

 

[PrairieDrifter]

My vote is head gasket or cracked head, get a coolant system tester, and leave the system pressurized for the night.

 

[BKING33]

U probably have a cracked head. Just finished replacing my 6.2. Same problem. My temp gauge was also fluctuating between 190-210. Also when I'd shut off engine it was bubbling in overflow tank.

 

[meowmeow]

Thanks guys, I purchased a block tester from Harbor Freight and I'll try it out when I get some time this week. If that shows no combustion gases (which I know is unlikely) I'll look into the pressure tester.

U probably have a cracked head. Just finished replacing my 6.2. Same problem. My temp gauge was also fluctuating between 190-210. Also when I'd shut off engine it was bubbling in overflow tank.

Just curious, did you replace the head gasket, heads or the entire engine?

 

[HotRodPC]

Blown head gasket most likely, possible cracked head. Compression is escaping into a cooling jacket somewhere.

 

[SirRobyn0]

Thanks guys, I purchased a block tester from Harbor Freight and I'll try it out when I get some time this week. If that shows no combustion gases (which I know is unlikely) I'll look into the pressure tester.


Just curious, did you replace the head gasket, heads or the entire engine?

Let us know your results. Also if you decide to open up the engine, remember you'll want to take the heads to a machine shop to be tested for cracks and checked for flatness where the head gasket goes, if you're not comfortable doing that yourself. Also if she's very high mileage or has other engine issues now would be the time to just go for the full rebuild.

 

[BKING33]

I didn't rebuild mine because it was an unknown engine pulled from a truck i stripped for parts. It had pretty severe blowby along with the bubbling coolant.
I didn't have the time to try repairing it, so I lucked out finding a low mileage Jasper engine for a fair price. I just actually got it back on the road.

 

[meowmeow]

Well I did the block test. The results unfortunately were that there is a combustion leak:

https://imgur.com/lx0MWmQ

I guess I'd need to open it up to know if it's just a head gasket or a cracked head or cracked block (common on the 6.2).

Also if she's very high mileage or has other engine issues now would be the time to just go for the full rebuild.

I'm wondering if it would be easier to just swap in a rebuilt or new engine rather than trying to rebuild mine. Like you said, it's definitely very high mileage and old. If I did the top end I'd have an engine with a new top end and an ancient bottom. I don't really have any experience doing this level of engine work and it while doing the head gasket/heads seems feasible for me, the bottom end I'm less comfortable engaging with. Is my logic sound or am I not right in assuming that swapping in a rebuilt engine would be easier?

Anyone know good places to look at prices for rebuilt/new engines?

Thanks

 

[SirRobyn0]

Well I did the block test. The results unfortunately were that there is a combustion leak:

https://imgur.com/lx0MWmQ

I guess I'd need to open it up to know if it's just a head gasket or a cracked head or cracked block (common on the 6.2).



I'm wondering if it would be easier to just swap in a rebuilt or new engine rather than trying to rebuild mine. Like you said, it's definitely very high mileage and old. If I did the top end I'd have an engine with a new top end and an ancient bottom. I don't really have any experience doing this level of engine work and it while doing the head gasket/heads seems feasible for me, the bottom end I'm less comfortable engaging with. Is my logic sound or am I not right in assuming that swapping in a rebuilt engine would be easier?

Anyone know good places to look at prices for rebuilt/new engines?

Thanks

Well just to confirm what you already know that is the color change that indicated combustion chamber gases in the radiator.

As I said before I'm more of a gas guy, so I'll say this if it was an old high mileage gas engine I would rebuild the entire unit or get an exchange the main reason being is all the components in the lower end that could have a problem down the road which would result in disassembly again. Plus disturbing a high mileage engine con in some cases set you up for lower end trouble soon than latter. Perhaps on of the guys more into diesel can confirm if that carries over, but I'd think it would.