Cooling system: vacuum failure

So, I've been trying to troubleshoot my cooling system, and to be honest, the system hasn't worked well since I got it, and I've had it for about 7 months. It worked better right after installing the new water pump, but never well.

I have replaced the water pump, upper and lower hose, thermostat, temp sensor, radiator cap, flushed the system multiple times (some dirt and rust, but not enough to believe that is it.

primary issue now is it is not pulling coolant back in from the reservoir. It can idle indefinitely, drive for 30 miles or so before the reservoir is overflowing and it starts to get hot.

i had bubbles when running the system open and in the reservoir when I ran the system closed. Attempted bars leak yesterday, still hasn't sealed (if I am right and it's a leak in the head/gasket.). There are other things that can cause bubbles, but I am not certain of anything at this point. Any advice on what to try next?

Hey, gard ~

If the timing is off, that will affect temperature. As well, of all the things you mentioned, you didn't mention flushing out the radiator cooling fins. I've seen dirt and gunk build up on the front of a radiator that caused overheating...including in my own D50, when I first got it. Spray from the engine compartment out. Even just a visual inspection will let you know if this is a contributing factor.


I'm not sure what to tell you about the bubbles.

Well, runs significantly worse after I added the leak sealant. Going to flush it again. Ugh. I am really lost, curious if I got a defective rad cap or thermostat. Honestly, questioning all of my labor so far on this cooling system. Might just buy all new everything again and start over, this time changing everything at once instead of over time. My thought is that, even on the new parts, as I fix something, the fault in the system isn't wearing out the parts as I install them. For instance, when I replaced the water pump and temp sensor, something else was still broken causing the pump to over work itself and by the time I have replaced something else the pump is worn out?!? Seems like straw grasping though.

Interesting, I will double check the timing, I did that myself, with new belts, when I replaced the water pump. I will also check the fins, I have ran water through them, but haven't tried a product on them.

Still dunno if that solves my vacuum problem where the coolant isn't being drawn into the system.

I'm not a first-generation guy, so perhaps someone here can add experience. On the 2nd gen. trucks, the thermostat has a certain position it needs to be installed in (an air gap at the top). Also, it's easy to install a thermostat backwards.

Don't beat yourself up :) we'll all work to get it resolved.

I questioned thermostat position multiple times against my manual, I am pretty sure I had it right it goes with the smaller phallac part in to the engine, lip flush to metal, then water pipe/housing goes on with the gasket on the water pipe side, being sure the thermostat seats in the ring indention on the water pipe/housing side.

could be wrong, but I think I have that right.

current one installed is for 170 degrees with a fail safe.

previous one was either 195 or 180.

it does raise the question if I need to hunt down one of these wax pellet thermostats from the manual, and if I should get a bypass or drill a hole in this one. The thermostat for the diesel in the manual looks unique, but all the parts databases have standard looking thermostats for it. They also come with rubber O rings to seal instead of the paper gasket, which I had to buy separately because the O ring setup is not compatable. The Aisin water pump had both the O ring and the paper gasket.

I am literally just trying to give all the info I have of my experience in case somewhere my mistake is the answer.

Pain in the butt tho' it may be, removing the radiator and flushing it upside down would back-flush any particulate settled on the bottom. Also, it allows you to spray from the engine-side of the radiator, some Awesome! sprayed on the front and back might be a good call. This is just what I did, and I got very good results.

The vacuum aspect and bubble problem I'm unfamiliar with...again, I know nothing about 1st generation trucks. As for the thermostat, it seems to me you want the spring to open towards the radiator - guys, correct me if I'm wrong.

What is the temp gauge reading...half way? Hot?

EDIT: Okay, I understand the vacuum thing - drawing from the reservoir back into the system. Are the hoses to the reservoir old?

There's a small diaphragm in the top of the radiator overflow return. If it's funky, it won't seal up the bypass port and the radiator won't be able to draw coolant back into the return. If the whole tank is looking rough, might be time for a new one...

Well, it's cold here today, but before dark I was able to warm up the truck, flush the fluid, and went ahead and took off the thermostat after I got home.

#1 the way it was installed.Attachment 21636



#2 the way I believe you are saying.Attachment 21637


#3 pictures in the manual. Attachment 21638Attachment 21639Attachment 21640

Note the picture of the thermostat itself. It looks nothing like a normal thermostat.

Thank you geezer! Are you talking about the cap? I took the time today to check the reservoir hose, as royster suggested, seems to be "okay" but does look aged, going to replace. And looked for what you could have been talking about. Are you talking about the cap?

Attachment 21641Attachment 21642Attachment 21644

Do do I just try and find a universal overflow tank that has a similar setup?

That cap should have a rubber gasket (diaphragm) in it.

Yeah that picture in your post (#3) is what a normal thermostat would look like - but it's a cross sectioned image. It would have a tensioner spring around the body of the wax pellet. And that black stuff in your overflow tank cap is all that's left of the diaphragm that Brad was talking about. Either find a decent overflow from a JY or one in the magical land of ebay...

Awesome. Started calling salvages, no luck, going to have to go in person to the pick and pull that I know has a couple of these trucks tomorrow. I found these on eBay, they look close, what do you guys think?
Attachment 21659Attachment 21660

Just popping in here, first off there isnt normally a gasket on the overflow tank since it doesnt need to be sealed.
On your tanks cap, there should be a hose coming off the bottom that drops down into the tank, i do not see it in your pic. Did you remove it for pic or not have one?

Next, thermostat should be installed as pic #1

Finally, if after fully warmed up, you have bubbles blowing into the radiator or overflow, you likely have a leaking headgasket or cracked head.
The heads tend to crack between the injector boss to valve and leaks compression into the cooling system.

Shame you started putting that garbage leak fixer stuff in, really gums things up

I do have the hose that goes into the fluid of the reservoir.

working on flushing that crap out.

I have suspected a head gasket leak in the combustion the whole time.

going to get some more flush product, follow royster's lead, remove the radiator and flush and back flush, get some hose to replace that reservoir hose, still going to follow geezer's advice and find a replacement cap and reservoir, but I did some reading and a leak in the system would cause the return hose to collapse and not pull fluid into the system. If it's a combustion breach, it pulls fumes from the breach when the system swells.

After cleaning it up again I will install another new thermostat and cap, new hose to the reservoir, inside the reservoir, and hopefully find a cap tomorrow. See what happens. If it's still not right I have an appointment Wednesday with a shop to do a pressure test and a dye test to confirm the head gasket issue. I really appreciate all the input, from everyone.

One thing you can do, leave the radiator cap off and let it run til its warmed up. Put your thumb over the inner hole of the radiator cap opening (sealing the rad with your tumb below the overflow hose)
Hold your thumb there for 5 seconds and then move it, if the headgasket is leaking you should get a little air puff when you release it.
Depending on where the headgasket/crack is, it may do it while cold as well

Quote:

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Originally Posted by gard

If it's still not right I have an appointment Wednesday with a shop to do a pressure test and a dye test to confirm the head gasket issue. I really appreciate all the input, from everyone.

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If you take it to a shop for a pressure test, have them check the radiator to be sure it's not partially plugged. Flushing the coolant system won't open radiator core tubes that are thoroughly blocked.

Quote:

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Originally Posted by FMS88

If you take it to a shop for a pressure test, have them check the radiator to be sure it's not partially plugged. Flushing the coolant system won't open radiator core tubes that are thoroughly blocked.

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which stop leaks will finish clogging if they were already partially clogged lol

I usually soak mine with acid lol

I've used citric acid powder dissolved in hot water. Did a decent job of munching deposits in both my radiator and heater core but you need to do it out of the truck as it can be aggressive on alloy heads etc. I did it to a friends old Mazda and it ate all the calcification in his heater core and turned it into a garden sprinkler lol.

I had a similar situation with my 2.6 gasoline that ended up being a tiny crack in the cylinder head. Mine would also happen at prolonged idle which I chased as air or coolant flow at a low idle speed. Finally bought a block checker and the solution turned yellow pretty quick. Diesels don't produce much heat at idle, so it's reasonable that it can idle indefinitely. My fingers are crossed for you. Hopefully it's just crud

The one truck I know of within 100 miles at a salvage had the cap. Hose was in good shape too.
Attachment 21663

Tomorrow the cleaning and flushing begins!!

I agree with everyone's analysis of the bubbles and suspected head or head gasket except for one thing. Gard that after driving for 30 miles his reservoir was overflowing. I've never seen exhaust gases cause coolant to expand and boil, bubble yes, boil no. It might be plausible, I've just never seen it.
One thing I have not seen mentioned is to cold of a thermostat. This only is if it is getting hot while driving. To cold and when the engine does actually start to build heat (not at idle as previously mentioned nor stop and go) it will be to hot and the thermostat will stay open. A cooling system has to have a thermostat hot enough to cycle and allow the coolant time to cool.
I'd still suggest the leak test (around $50 from Napa and easy to do yourself) but also have that cap pressure tested and test that thermostat in some boiling water (you should see it open when dipped in the water and close when removed)

It really depends on the size of the leak. I once did headgaskets on a friends gm 3.4 v6. That thing would be viciously boiling within 5 minutes of starting cold. When I had the head cracked on my 2.6, it would only boil if it had bubbled long enough and run the coolant low.
Sometimes the air pockets will vent out of the cap easier than expanding coolant. If the cap is less than perfect it will vent the pressurized air much more quickly than coolant, and sometimes below the pressure rating on the cap. When this happens the pressure in the cooling system drops, lowering the boiling point of the coolant, and sudden violent boiling follows

Well, I got the new reservoir cap on, and a new radiator cap, bubbles galore, ran it open as well and now it's just continuos bubbles. It's a head breach, gotta be, at this point. Started breaking it down yesterday, had to get some tools, a flexible extension, and swivel for getting to the harder bolts and a socket driven Allen set. Got the radiator off and started cleaning it hard core. Still getting sealant out, I'm giving it a once over then taking it to a radiator shop to get all the love they can give it.

I should have the head off today, confirm if it's a gasket or a crack. I've got a gasket, but I am considering doing the 56 swap anyway, reading on here, it is quieter and maybe better?

this is the right head by your guess? And the ARP bolt numbers in the diesel section are what I want as well?
Attachment 21695Attachment 21696

if you order ARP you are looking at a 2ish week wait, and i think it was $430 for everything lol. I will say i liked the arp better lol

Head wise, the d55 and d56 head are the same, the only difference is the cam and rockers.

Head wise pay attention to the flush or protruding valve types. To replace the 55 with a nice roller 56 head I believe you need protruding valve (the head I pulled off mine was protruding valve so that's what I got for the 56 replacement)

Oh and try to find a good top end gasket kit that includes new injector nozzle gaskets (copper washers). Mine did not have them

Thanks for the info. Did some reading on the valves and injector sizes. Should be warm enough to get out and try and get it off to check valve type. Where did you order yours?

Will a harmonic balancer from a 56 work for the 55? Mine is chewed up. Can the key slot be repaired/replaced?

Quote:

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Originally Posted by gard

Will a harmonic balancer from a 56 work for the 55? Mine is chewed up. Can the key slot be repaired/replaced?

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it will fit, but there is like 12 different style balancers between the 4d55 and 4d56 lol.
The most common one on the 4d55 is the really wide single vbelt, d56 never had this one

https://www.ebay.com/itm/HEAD-GASKET...-/253697957494
Headgasket set i used with my 2 turbos and 30psi

I replaced my injector copper. I think it came in that gasket set

EDIT - they did, they are in the pic lol

I got mine off eBay. Pricey but the seller had a good listing that specified valve type and injector size with warnings about checking both because returns were not accepted for an incorrect order. Gave me a little confidence (warnings of getting Chinese junk parts through eBay made me wary) because they had experience with this head in particular. I did look up the seller but it looks like they are dormant.
If you go with eBay just take your time and read everything, others here may have seller suggestions or other avenues entirely for a new head.

For the balancer, I don't see why a 56 would not work on a 55 but I have not done this.
Has anyone else?
A machine shop might be able to repair it but I would call around if you want to try, I've never seen one get rebuilt only replaced.

Skullzaflare,
Did you ever worry about head gasket thickness or is that only for the newer d56?

Quote:

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Originally Posted by Bjamin

Skullzaflare,
Did you ever worry about head gasket thickness or is that only for the newer d56?

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i try to stay thin, but i went to the gasket listed, which is a MLS gasket instead of a composite gasket

I made sure to go with a Multi Layer Steel gasket.
I only asked because I watched a video the other day on doing a 56 head gasket and the guy had to measure the piston protrusion at TDC and pick the correct gasket thickness, I hadn't seen it mentioned anywhere else.

I think I found the pulley. But it's a site that might be shady cause I've seen the page layout under multiple names. Also think I found it on amazon, gotta read more, but it looked like it.

Really appreciate the help. Been pretty cold here (for Arkansas) hard to get much done since one outside working on it. Should have this off by the weekend if rain holds off. Then making my orders.