Pressure under the coolant cap

tjkj2002 · **Posted:** Thu Jun 05, 2014 10:16 am

racertracer wrote:

Ok. no pressure under the cap after my morning commute yesterday and no bubbles in the glass of water.

Engine temps recorded using the laser temperature gun.

187 deg - top of thermostat.

184 deg. - at valve cover.

158 deg. inside the coolant bottle, cap removed.

At those temps,even adding up to 5 degrees for temp gun inaccuracy your not even at the t-stat opening temps.At those temps your not ever going to have a lot of pressure with a 195 degree t-state as the coolant is not circulating fully.Your cooling system,if properly functioning, is designed to hold pressure up to about 260 degrees with a 18psi cap,about 250 degrees with a 16psi cap.

Your average 195 degree t-stat only starts to open at 195 degrees and usually is not fully open till about 218 degrees.

CGman · **Posted:** Thu Jun 05, 2014 11:37 am

geordi · **Posted:** Thu Jun 05, 2014 3:21 pm

Is this a standard thermostat or the in-hose?

My suggestions for you: maybe a static pressure test is your best bet. Pump up the radiator system to 15 lbs and let it sit for at least a few hours or maybe overnight. If the pressure holds, then I would say you don't have a pressure issue. The water shouldn't expand much if it isn't actually crossing the 200 degree mark anyway.

I don't know if the CRD would normally have pressure or not at lower temps, but my CRD drove around for an entire Savannah Summer without the metal fan even installed, and never had a heat problem. Didn't lose water, didn't seem to have any pressure issues... But I will admit I wasn't opening the cap like you are, looking for pressure.

If there isn't any exhaust gas in the water, I don't know if you should even keep worrying about it. I'm concerned about the transmission in my Jetta TDI right now, and I have to keep telling myself to just shut up and drive, and stop being hypersensitive. It is a (newer) transmission, and the car moves and drives fine. Could it be snappier? Maybe. But this trans has 150k on it and maybe performs a bit differently than the old one. That doesn't mean that it is out of spec. Just different.

If there isn't CO coming out or water disappearing, then the system is probably working fine. So what if it doesn't have pressure right now, maybe this engine is being more thermally efficient than the old one. That is actually a good thing.

Diesels naturally run cooler than gassers anyway, so being able to resist 268 degrees is NOT a benefit - the engine would be severely damaged at that level of overheating anyway.

Sent from my iPad using Tapatalk HD

racertracer · **Posted:** Fri Jun 06, 2014 9:56 am

Geordi, I have an oem thermostat.

This morning ambient temp outside was 61 degrees F.

Top of thermostat 189
Top of valve cover 187
Top of viscous heater 190

No pressure under the cap.
No coolant loss.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The CRD uses a 180 F t-stat and is full open at 207 F. Your cooling system is functioning normally. 90% of the time the CRD will run between 175-210F. It can see a peak of 239 F pulling a trailer up a grade with the AC on. At this point the overheat protection is reducing fuel by up to 50% and the vehicle slows down considerably. If the coolant temp passes 245-250F the engine will limit itself to about idle.

The pressure under the cap can vary from 0-8psi in normal conditions based on ambient temp, AC, load. etc. If there is no evidence of coolant in the overflow portion of the hot bottle, the head gasket is fine. Drive it until it rusts out

geordi · **Posted:** Fri Jun 06, 2014 10:38 am

Thank you Keith for being a voice of reason.

flman · **Posted:** Fri Jun 06, 2014 5:12 pm

GreenDieselEngineering wrote:

The pressure under the cap can vary from 0-8psi in normal conditions based on ambient temp, AC, load. etc. If there is no evidence of coolant in the overflow portion of the hot bottle, the head gasket is fine. Drive it until it rusts out

Exactly stop over analyzing pressure or lack of pressure. :JEEPIN:

racertracer · **Posted:** Fri Jun 06, 2014 7:12 pm

Yeah, well I'm a little edgy... considering.

But, how do you explain the explosive pressure and pressure under the cap after the one minute run and now no pressure at all now.

DOC4444 · **Posted:** Fri Jun 06, 2014 8:03 pm

Perhaps head gasket leaks when cold, allowing combustion gas to pressurize the cooling system, then the aluminum head expands with heat and HG seals?

DOC

racertracer · **Posted:** Fri Jun 06, 2014 8:21 pm

Doc, i am planning a pressure test tomorrow morning. Checking for external leaks.

racertracer · **Posted:** Sun Jun 08, 2014 2:27 am

I rented a radiator pressure tester and there was a loss of pressure within one minute.

Observations so far:

The ambient temperature outside was 55 degrees humidity 88% and I noticed condensation on the windshield interior passenger side.

Is this indicative of a heater core leak, how do I check for that?

I will soon be checking the coolant hoses leading to the EGR valve and the hoses to the oil cooler for leaks.

geordi · **Posted:** Sun Jun 08, 2014 2:48 am

Bypass the heater core, connect the two hoses together to keep the system sealed. Do the pressure test again. If it doesn't leak down... Then you have found the culprit, and your interior will probably need to come out.

It is a logical hypothesis and unfortunately a common problem with Chryslers. The older Jeeps have substandard metallurgy in the cores, such that either the heater core will rot out, or the AC core in some cases, from some form of chemical attack by the normal stuff passing through it. Cheap parts.

racertracer · **Posted:** Sun Jun 08, 2014 3:02 pm

OK, I disconnected the hoses to the heater core and looped them back to the system.

I have pressure under the cap now, so from what I can comprehend, the cooling system is running fine and should have been this way from the beginning. So I have a bad heater core that needs replacing.

I bet replacing it is going to be a PITA.

I will be monitoring the system for a while to see if the leak is really gone.

I want to thank Ranger1 for contacting me via IM and walking me through this CRD repair episode.

And everyone else with their advice also.

Thank you

papaindigo · **Posted:** Sun Jun 08, 2014 3:33 pm

Thoughts:
1. if rental of the radiator pressure tester was cheap I'd consider grabbing it again and checking pressure now that the heater core is bypassed. Alternatively the HVAC box has a drain, for removal on condensation, that exits the firewall somewhere under the coolant bottle. If you can get to that drain do the "taste" test for antifreeze (should be sweet) dripping out of that drain. If so no need to redo the pressure test. I recommend this to make absolutely sure the heater core is leaking as replacement is..., see below. It's possible the loss of pressure during the test was related to a heater hose fitting leak due to a weak spring clamp (very common as clamps age and especially if they have been reused)
2. servicing it is going to be a bear. Like all vehicles built since the 1960's (on a '65 Mustang you just popped a few spring clips to get direct access) you cannot get access to the heater core without removal of the HVAC housing and a good bit of the dash including, I strongly suspect, purging and recharging the AC. That's the bad news. The less bad news is there is nothing special about the CRD dash/HVAC as opposed to a gasser KJ so if you know a good local automotive AC service place they can do the work rather than chancing a dealer if you confirm the leak and decide not to do the repair yourself.

geordi · **Posted:** Sun Jun 08, 2014 5:30 pm

Good call on the spring clips, but a faster and more conclusive way to validate the heater core would be to do an isolated pressure test.

It may take some creative plumbing, but if you can cork one side of the heater core outlets and apply pressure to the other, that would do it. No more than 16psi (shop air if you can properly regulate it) and if that leaks down... Bingo.

It certainly is frustrating that the heater cores can STILL rot out, considering how much of a bear they are to dig out and replace. This will be an all-day job of getting to know your interior. Unless you are a Zen Master, I would strongly suggest letting an AC shop have at it. I have done heater cores (or a similar level of deep-in-the-dash) on 4 different vehicles, 2 VW, one Ford and one Mopar... There were snapped tabs, pinched and bloody fingers, and much cussing with each.

Maybe an external electric heater for this winter is a better idea, and just leave the effing thing alone? :mrgreen:

It'd be easier!

racertracer · **Posted:** Tue Jun 10, 2014 9:18 pm

OK, here are some quotes on replacing the heater core.

Dealer 1. $1150 labor, plus parts, approx. 1,400 to 1,600 dollars + tax.

Dealer 2. $1,600 plus. + tax.

Dealer 3. $1,400. + tax and related parts.

Here is just a blip of what to expect when DIY.

video... on YouTube:

https://www.youtube.com/watch?v=n8Rj25nDMX8

Has anyone ever used a cooling system leak sealer solution called K-Seal to repair a heater core leak?

http://www.kseal.com/heater-core-failure-and-repair/

thermorex · **Posted:** Wed Jun 11, 2014 8:18 am

racertracer wrote:

OK, here are some quotes on replacing the heater core.

Dealer 1. $1150 labor, plus parts, approx. 1,400 to 1,600 dollars + tax.

Dealer 2. $1,600 plus. + tax.

Dealer 3. $1,400. + tax and related parts.

Here is just a blip of what to expect when DIY.

video... on YouTube:

https://www.youtube.com/watch?v=n8Rj25nDMX8

Has anyone ever used a cooling system leak sealer solution called K-Seal to repair a heater core leak?

http://www.kseal.com/heater-core-failure-and-repair/

So I guess Raf will start having fun replacing the heater core, lol. Come on, is not as bad as it looks...

DOC4444 · **Posted:** Thu Jun 12, 2014 9:54 pm

Based on four years of experience with K-Seal in our Kubota BX-22 diesel tractor, I would seriously consider it. Kubotas are notorious for water pump problems and they are a PAIN to get to, to replace. After the second one only lasted a couple hundred hours before it was pissing coolant out the weep hole like a large water gun stream, I was about to shoot myself. I ordered another ridiculously overpriced water pump and then discovered K-Seal. It has completely sealed the horrible leak for four years and the tractor runs much cooler in hot weather when running at full power.

They claim it does not plug up water passages or radiators. Based on my experience, I would be inclined to believe this, but I do not know enough to guarantee no problems.

Hopefully, someone will respond with actual KJ CRD experience.
You should start a new K-Seal thread to get maximum attention and feedback.

If in your situation, I would be inclined to try it. Use a full small bottle to start and put it in the header tank after sucking out some coolant. It will take several heating/cooling cycles to fully distribute it and you will need to keep your heat on full throughout to get it through the heater core.

DOC

racertracer · **Posted:** Thu Jun 12, 2014 10:20 pm

Doc, It didn't work. Flushing the system out this weekend.

DOC4444 · **Posted:** Thu Jun 12, 2014 10:48 pm

I would try a second small bottle and at least 5 or 6 full heating/cooling cycles before giving up.

You have nothing to lose but the cost of another bottle and a few days......

DOC

Pressure under the coolant cap

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