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No coolant system pressure

osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
My truck doesn't build any pressure. It had weak heat last winter. I swapped rad cap with a lev r vent and I get nothing. Cap doesn't even get hit. Rad is hot, hoses are hit, runs great. Doesn't smoke. I see no wetness but I will double check block(freeze plugs).

It has 203k miles, newer rad hoses and heater core bur it may well have stock water pump. Is it possible the vanes are worn off and it's just not moving the coolant effectively enough to build pressure.

Every now and I smell coolant at startup but I think it's defective heater core(currently bypassed for summer due to breaking the valve). Doesn't noticeably use any coolant.

It's got me stumped I guess, i put some leak stop in when I got it but most of that's been flushed out in the last 6 months. it wasn't leaking idk why I did it.

It's my dd I put 200 miles a week or more and I've never seen the temp really move except at startup. ( I.e. Cold to "o" on normal)
 


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ricco750

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Springfield, MO USA
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'93XLT4X2 (3:27 LimSlip)
It sounds to me like the thermostat may be bad. Just because the radiator is hot to the touch does not mean the temp is where it should be. I would change the t-stat, make sure you get all the air out of the system, and then see what happens. And if this works, you will probably accelerate the leak in your heater core, and will need to replace that as well, which is easier than the t-stat change as well.:thumbsup:
 




osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
It sounds to me like the thermostat may be bad. Just because the radiator is hot to the touch does not mean the temp is where it should be. I would change the t-stat, make sure you get all the air out of the system, and then see what happens. And if this works, you will probably accelerate the leak in your heater core, and will need to replace that as well, which is easier than the t-stat change as well.:thumbsup:

Well the heater core is/was bypassed. No change in pressure either way. Thermostat is functional. I will probably have to rent a pressure tester. I hope its the rad (I have another one thankfully) or the cap (cheap). Its a stant lev r vent cap and it doesnt do anything when you pull lever. When I drained the coolant when i did my lower intake gasket and filtered the coolant with some shop rags and I had a huge ball of crap after words. It was unbelievable.

Would the rad being plugged cause pressure issues? I just bypassed the coolant valve and hooked the heater core back up and it has good heat (its about 50 in the morn here). The no pressure worries me though.
 




osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
Well i grabbed a water pump and elec fan. Turns out there was a pinhole leak behind shroud that was enough to leak pressure but no show any obvious signs.
New radiator fixed that.

So any other things to look for with heat issues?
-changed heater core
-changed thermostat
-new water pump
-new radiator
-elec fan
-flushed system

Temp is always good, heat works only OK.
My previous RBVs and my buddies current b2 annihilate this thing for heat.
MY a/c is non functional. I put this on max a/c and its better but on everything else it takes like an hour to get blistering hot heat out of the vents (still not as good as b2 after like 10 minutes), all the while the temp guage is fairly steady. Could it be internal? I checked the cable and arm and those seemed to have full range of motion.

It's prolly petty as the heat works for the most part, but I know these vehicles are capable of better heat and I would like to know why it isn't getting it.
 




osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
Still no pressure. I'm at a loss. No obvious coolant loss, no coolant in oil.

Would an air pocket seriously cause a complete lack of pressure in system. I can remove rad cap when engine is at temp with no issue.
 




Roadrunner777

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Bemidji, MN
Year, Model & Trim Level
94 4x4 Sport 88k
Rent the pressure tester. Now, something to chew on... I just replaced my thermostat earlier today. Afterwards, I drove it a good bit to get it up to temperature, and then opened my cap. I didn't get a lot of pressure either, not compared to other vehicles I have owned.

Here's something funny: I took out my mechanical fan to replace it (cracks) and got ready to replace the thermostat and realised I couldn't get to one bolt without a universal, which I recently broke. So, it's a cold day (it was about 35 degrees at the time) so I drove the 10 minute to the store without a fan of any kind. The engine was quite happy, the temperature swung normally... I think these systems do run on the cool side, assuming nothing serious is wrong. It takes my heat quite a while to get going. I'm going to block of the radiator for the winter, and use a seat heater I just put in.

Do you still have that heater bypass gizmo installed? If so, I'd replace it with straight nipples. Might be a restriction there.

Max A/C opens a door for outside air instead of recirculating. I wonder if you have some stuff in there blocking your flow. Have you done the blower/resistor removal to clean out crap that catches on fire?
 




osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
Well I picked up another thermostat. So when I pull the old one it had crap clogged in the bleeder hole. Voila there was an air pocket. I just flushed this thing 2 weeks ago and the coolant is horrendous mud color.

I did remove the gizmo.

Max a/c recirculates the air not bring in fresh air fwiw. And that valve also works.

Is yours an auto trans?

My last one was and I drove for over a year with no fan. The manual trans (mine) have single core radiators vs the two cores the autos have. Mine isn't as happy with no fan lol. I luckily had an Efan laying around. I went and bought the $37 controller from advance auto and it works.

Side note: the 16" fans at autozone/advance don't flow nearly enough air. With ambient temps in the low 50's it works ok but when it's in the 70's it isn't enough while idling. Although with the heat in it will but who wants the heat on when it's 70 out?
 




Roadrunner777

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94 4x4 Sport 88k
Yes, auto with the towing package.

Thanks for the correction on the MAX A/C and the door. I have been playing with an issue on that and it changes my troubleshooting direction.

I'm on the fence about electric fans. I don't drive many miles, so gas mileage is almost a non-issue, and... it's hard to explain, I just feel like going old school with this one. I think I am getting nostalgic in my years. (Of course I did just install a seat heater, didn't I... LOL)
 




osteologation

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City, State
Caro, MI
Year, Model & Trim Level
1994 Sport
Yes, auto with the towing package.

Thanks for the correction on the MAX A/C and the door. I have been playing with an issue on that and it changes my troubleshooting direction.

I'm on the fence about electric fans. I don't drive many miles, so gas mileage is almost a non-issue, and... it's hard to explain, I just feel like going old school with this one. I think I am getting nostalgic in my years.

My experience with this particular fan/clutch has always been poor. I would like the E-fan to work but if I go back to MECH fan I will use an auto radiator and fan assembly. AN run my power steering through the radiator in lieu of the auto trans.
 




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