Hi All,

My truck puked coolant for the first time since I have had it. It has head studs and the EGR cooler is deleted. I was pulling a 24 ft enclosed trailer weighing about 4000-4500 lbs through some mountains but nothing terribly hard. Truck has Atlas 40 FICM tunes and 8K tow tune from Gearhead. Every parameter I monitor is solid, EOT and ECT delta is 6-8 degrees, I don't let my EGT get past 1250 for any meaningful amount of time, the truck does have a 200 degree mishi tstat. The only time my coolant temp has ever gotten anywhere near the 230 mark is pulling a trailer up steep grades when it is 90+ degrees outside.

It is possible the coolant could have been a little overfilled because my driveway isn't very flat and depending on how I park the truck drastically changes the coolant reading. I really need to find somewhere flat to park it overnight and check it.

It puked on the trip to where I was going but I ran it hard on the trip home and have ran it hard since then with no puking. I did replace the degas cap with one of the aftermarket non clicky types after it happened.

I don't have a great reading on the coolant level but there is still coolant in the bottle so I would think there is enough there it would puke under high pressure rather than just vent air which I may not see any evidence of.


If I had blown head gaskets would I normally expect it to continue to puke each time it is run hard and have any other noticeable symptoms?

Thanks!

 

I assume you used OEM head gaskets?

How long ago were the head studs installed and are you confident in the person/shop that installed them?

Are you confident that your coolant strength is good (ie 50% mix)?

I would recommend installing a pressure gauge on the coolant system to see if you actually are exceeding the 17 psig.

 

I bought the truck with studs already in it. I think I remember seeing the receipt showing that it was OEM gaskets and they definitely told me it they were OEM gaskets. I can only hope that they are, I can't know 100% for sure.

Don't know who installed them.

Coolant strength is definitely 50/50

Can I just get a gauge and T it into the small hose from the radiator to the degas bottle?

 

yes. If you want to see what the pressure does when running/driving, you can install a long hose and run it into the cab, but definitely be careful doing that for obvious reasons. The hose can slip through the opening on the hood if you don't close it all the way.

 

Ok, I will get a gauge and give it a shot.

 

I know the cap is well known for eventually failure and can start the puking process.
Since you've changed the cap now, I'd see if it happens again with heavy towing as it might just be that simple...a cap.

 

Yeah, I am hoping so. I also remember thinking last time I worked on the cooling system that I may have put a too much coolant in because of the angle of my driveway it can be kind of hard to judge and this is the first time I have towed anything and really pushed it since then so that could be part of it. That said I was able to get everything I need to test it for about $25 and I would rather pay the money and either have the peace of mind or know what I have to deal with.

 

Well I hooked the gauge up to the cooling system and as the truck warmed up it gradually climbed to about 11 psi and then it was solid no matter what I did it wouldn't pass 12 psi. Coolant temp hung around 202 because I have a Mishi 200* stat. I am going to hook my trailer to it and go find a hill tomorrow and see how it acts but it definitely didn't build enough pressure that it should have vented.

 

I would go with the cap minus any other indication.

 

Yeah, I am hoping so. I got the fittings to move my Edge pressure sender from my fuel pressure to coolant pressure so that I can easily monitor it from the cab with the hood all the way closed and without a hose running into the cab. I don't run very hot tunes at all so my fuel pressure never drops and my fuel pump is only a year old so I should be plenty safe to monitor coolant pressure for a while rather than fuel pressure. I will stress it later with my trailer and see what happens.

 

Well now that I can watch the pressure easily in the cab I drove it to work which is about 50 miles and mostly freeway. I am even more confused than before. The "normal" pressure for the current situation seems to actually be 14 PSI, after I had been on the freeway for a little bit that is where it settled. When I really get on it the pressure will actually drop a few 10ths of a PSI and then after I let off it will raise about .3-.5 PSI pretty slowly I assume because the coolant is a little hotter from the higher load. The highest I saw was 14.5 PSI but it never spikes up when under load and always gradually returns to 14. Here is the part that has me really confused, it will be at 7 PSI after driving for a little bit after a cold start but like clockwork when ECT hits 200* it will go from 7 PSI to 12 PSI in about 15-20 seconds (it has done this twice now so I don't think it is a fluke) even if I am coasting it just keeps climbing until it hits 12ish then it more slowly rises to 14. So that begs the question if I didn't have a 200* tstat so that the ECT stays closer to 190 would I ever see that 5 PSI spike because if not my normal pressure would be 8-9 which seems much better. Something weird is happening but I am not convinced it's my head gaskets. I am going to check my coolant strength with one of those testers and see what the boil point is. Anyone else have any ideas why I would gain 5 PSI of coolant pressure so quickly at 200*? That is the temp my thermostat opens at but I can't figure how that would have any effect on the pressure especially an increase in pressure. I might pick up an 192* tstat and see what kind of results that produces.

One other thing to note is if I get into it with the engine cold and build as much boost as I can I don't see any spike in cooling system pressure at all. I also have some injector stiction issues so it doesn't run great cold but I can still build a fair amount of boost.

 

Kdawg,
Running your boost up when cold, knowing your thermostat is still closed, shouldn't have much affect of psi while accelerating. The water pump may help pressurize if the thermostat is open but really with it closed, you shouldn't see much change.
I would expect a quick spike in temp as noted until the thermostat opens and then level off.
I don't see any alarms in your notes above to identify a specific issue.
The guesswork continues.

 

Well my thoughts were that even with the thermostat closed a spike in pressure under hard acceleration would point to head gaskets.

All the way up to 200* it stays at about 7 then at 200 really quick gains of an additional 5 or so PSI. That doesn't seem normal to me, something is happening at 200* causing a rise in pressure. I may put a 192* tstat in it and see what happens.

I did test the coolant strength and according to this tester it has freeze protection to -29 degree Celsius which from what I can tell is about 47% coolant 53% water. So the mixture isn't a perfect 50/50 but I would think it is close enough to not drop the boiling point enough to cause my issue. I will get some more full concentrate coolant and bump it up though and try and get it to 50/50.

It has also been sitting on level ground all day so when I leave work I can accurately check the coolant level and make sure it isn't overfilled.

 

even 60/40 is close enough. The temperature plays a huge roll and I'd suspect the difference of 192-200* is about 4-5lbs. I think I read somewhere that for every 2* is 1lb... but your below 16lbs and leveled at 14*.

That jump is the T-stat opening and letting the primary coolant that was surrounding the cylinders mix with the rest of the coolant and finally hitting the sensor. It was also at a higher pressure until the t-stat opened, then it should equalize both temp and pressure over-all. I wouldn't worry unless your blowing the cap off every time you drive it hard.

Take a pressure tester to the system, that will show a leak if your that worried. The pressure has more to do with the boiling point than most will admit, it prevents bubbles from forming even when the liquid is hot enough to boil.

 

The pressure rise is certainly temperature dependent, but also the level in the degas bottle plays a part. The more vapor space left in the degas bottle, the lower the pressure rise will be. I did some estimates years ago, but didn't save the work.

This is another reason to keep the maximum liquid level at the "minimum mark".