| Author |
Message |
DuncanS
Samba Member
Joined: October 17, 2013
Posts: 4583
Location: New Hampshire
|
 Posted: Mon Aug 08, 2022 4:59 am Post subject: OK to run without coolant pressure cap? |
 |
|
'91 DD 2WD coolant loss from a crack in the reservoir. Leaks only once pressure has built up. New one with cap on order from GoWesty.
If I drill out the pressure cap so it communicates directly and all the time with the overflow tank, will it be OK for 30 mile trips until the new one arrives and is installed? Two questions here. Is 212º OK as an operating temp, and since the radiator is higher than the OF tank, will it pump the coolant out through the unsealed OF tank cap until the radiator is only half full? Do I need to make a temp OF tank from a jug and mount it up inside the cab?
Duncan |
|
| Back to top |
|
 |
djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32634
Location: Reading Pennsylvania
|
|
| Back to top |
|
|
DanHoug
Samba Member
Joined: December 05, 2016
Posts: 4800
Location: Bemidji, MN
|
| Posted: Mon Aug 08, 2022 5:35 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
the design of a cooling system being under pressure of course raises the boiling point of the coolant. this has an important function of preventing micro-boiling-- small boil bubbles that form on the low pressure intake side of the water pump but also on the hot spots of the cylinder and head and then SLAM shut! this causes cavitation erosion and can wear metal away.
does that happen in a 30 mile drive over a span of two weeks? dunno. as Dave suggests, driving with a janky tank is more of a risk due to catastrophic failure.
with regard to the rad draining back, so long as there are no air leaks in the rad or plumbing, i suspect it will hold enough vacuum to prevent things from draining out... sorta like a chicken waterer with a mason jar over a pan.
there's not someone close by with a tank you could get in quick order? i've got one i could send out but there's got to be one closer.
_________________
-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
|
| Back to top |
|
|
vwwestyman
Samba Member
Joined: April 24, 2004
Posts: 5688
Location: Manhattan, Kansas, USA
|
| Posted: Mon Aug 08, 2022 7:06 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
I once drove around in my diesel Rabbit-powered Cabriolet with the radiator cap loose because it had a little tiny pinprick of a head gasket leak that was over-pressuring the cooling system with exhaust. Even with some longer trips.
I think I started that after it split the hose from the head to the radiator from clamp to clamp. To limp it to a place to replace the hose, we took most of a roll of duct tape and wrapped it around the hose!
No observed negative effects after replacing the head gasket.
All that to say, it's likely possible.
But if you have something else you could drive until the new parts arrive, that would certainly be much safer.
If you're in a pinch and can't wait, it would probably be ok; just slow down a bit and keep an eye on the gauge and coolant level and carry a few jugs of water just in case.
I'd probably scuff up the plastic on the coolant tank and give it a healthy coating of some kind of epoxy to seal up that leak; the coolant may prefer to exit via the crack than to go into the overlfow tank.
_________________
Dave Cook
President, Wild Westerner Club
1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing |
|
| Back to top |
|
|
jimf909 
Samba Member
Joined: April 03, 2014
Posts: 7478
Location: WA/ID
|
| Posted: Mon Aug 08, 2022 7:18 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
Here's a good thread including tencentlife's expanding on DanHoug's point.
Drive it for 30 miles a few times? I'd consider doing it only if I had no other alternative (other car/motorcycle/bicycle, not make the trip, etc.), the trip was absolutely necessary and I was ready to wait 2-4 hours for an AAA tow if coolant tank fails and coolant is lost. I once did notable damage to a wbx driving 20 miles with a cracked H pipe. I thought I could manage temps but was wrong.
https://www.thesamba.com/vw/forum/viewtopic.php?t=521732
| tencentlife wrote: |
A normal system will generally develop about 10psi internally, although higher transients can be expected. So the cap blowoff capability does not come into play most of the time, but does need to be there and working. The pressure containment accounts for the majority of the increase in boil point. What is often overlooked is the suppression of cavitation and spot-boiling that containment offers; I can guarantee that those running non-pressurised systems are experiencing increased spot-boiling in the cylinder head. How do I know? because minor spot-boiling occurs even within a pressurised system (and is one reason for the high-pressure transients), so it's going to be even greater without suppression. And I have observed numerous systems with a non-holding cap spot-boil badly enough that they were diagnosed as having combustion seal leaks when all that was being seen was coolant vapor, not combustion gases, reaching the pressure bottle. Spot-boiling results in decreased and uneven cooling effect at those hottest head surfaces, as well as erosion of the surfaces. Cavitation occurs mainly at the water pump impeller and can erode the impeller and volute, shortening water pump life and lowering flow rate as the pump loses efficiency.
The higher viscosity of glycol mix does aid in boil/cavitation suppression, but not as much as pressure containment does. The temptation might then be to increase the glycol component to have higher viscosity, but that would work at cross-purposes because glycol is much less efficient a heat absorber/rejector as plain water. Antifreeze mainly performs its eponymous function, boil point increase being relatively minor compared to freeze point decrease, and it offers controls to corrosion, cavitation, aeration, and other negative factors that were serious problems in early water-only systems.
Some people do run open systems and get away with it, as these effects are not immediately apparent but they are occurring nonetheless. As power demands and especially elevation increase, though, the negative effects become greater; at high elevations such as where I reside, open systems have been immediately problematic.
People often point to the Evans open cooling approach and use that example as a free pass to run their own system open, overlooking the fact that the Evan's coolant has a proprietary additive package designed to manage these and other effects.
So bottom line is, open system can be done and things don't immediately blow up, but there are unseen negative effects occurring constantly that would be better-controlled with containment. A pressurised system lets the engine be operated safely in a much wider range of heat and load conditions, and that is why no manufacturer has sold a vehicle using a non-pressurised cooling system since the advent of such a thing, it's overwhelming benefits were so obvious to the vehicle designers.
If you want to run an open system just to prevent leaks and ruptures, just be aware that you are only applying a band-aid, there are no leaks and ruptures when the system components are kept in good condition. |
| morymob wrote: |
| Guess i'll add my 2-cts here on no-press.Done it sincr '93 on ALL my wbx's,5,to date and no blown,split etc parts. One, a '94 was driven almost 14 yrs and i put well over 100K on it, had 330K when i sold.Each has their own theory(?) as what goes on in the engine but NONE have over heated or was a problem. I also stated each time to insure the cooling system was up to par to start as it should be anyway. U do it your way and i will keep on keeping on, i rest my case. |
_________________
- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
|
Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
|
| Back to top |
|
|
DuncanS
Samba Member
Joined: October 17, 2013
Posts: 4583
Location: New Hampshire
|
| Posted: Mon Aug 08, 2022 7:21 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
Thanks so much guys. I had canceled the weekend event, because I don't want to go out with a jury rigged coolant system, so no info on my awning program. Or as the wrong sided steering wheel guys say--programme.
OK, so there are a ton of other things to do on it and around home, so will concentrate on them. Such as the mysterious PS brake light which comes on periodically. Goes out when I kill the negative ground switch. Does not go out when I pull the fuse or either of the brake light switch leads. Somewhere there has to be a leak from a hot-all-the-time lead (30) to the R/BK lead to the brake light. They are LEDs and if I take out the PS and put it back, the DS comes on. Never two at the same time and the brake lights don't work with the pedal forced down.
Intermittent voltage stabilizer. I thought semi conductors either worked or didn't. No semi working. Yes there is supply and ground to it when it won't produce the 9 ish volts, but maybe it's too small a current flow because of a poor connection somewhere from the 14 pin connector lead to the device itself.
Sigh--Last straws in abundance. Gas gauge is the odometer.
Duncan |
|
| Back to top |
|
|
Abscate
Samba Member
Joined: October 05, 2014
Posts: 22670
Location: NYC/Upstate/ROW
|
| Posted: Mon Aug 08, 2022 7:30 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
This is why you want old people with experience and not young theorists on fora
30 miles at 60 mph with full engine heat load, no.
30 miles keeping it at 30-40 mph at max torque at atmospheric pressure? I’ve probably nursed home 15 euro cars home thst way.
_________________
.ssS! |
|
| Back to top |
|
|
vanis13
Samba Member
Joined: August 15, 2010
Posts: 3100
Location: ABQ NM USA.... Except when not
|
| Posted: Mon Aug 08, 2022 7:41 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
1) Yes you"can".
Many have run with a failed cap that functions like no cap - you could blow/suck through the cap without resistance.
My friend has been unknowingly driving like this for maybe a year. I pressure tested her her system this week and am fixing all sorts of leaks that showed up at 15 psi that didn't leak for her with a bad cap.
2) the tank and cap can be had at AutoZone for $20 (in 2 days if not at your actual store) IDK how it compares to tanks from elsewhere but it's a Dormant product and a quick and cheap (and likely permanent) fix until your other tank gets in
https://www.autozone.com/cooling-heating-and-clima...597612_0_0
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace
www.SuperVanagon.com - some stuff I make |
|
| Back to top |
|
|
Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50353
|
| Posted: Mon Aug 08, 2022 7:47 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
| A decade back, I drove my one of my Vanagons for quite a while with a drill cap and no pressure in the system. I did not limit my speed or load. Coolant use was minimal maybe a cup every 2000 miles. So long as you are paying attention I don't think it is a big deal. |
|
| Back to top |
|
|
DuncanS
Samba Member
Joined: October 17, 2013
Posts: 4583
Location: New Hampshire
|
| Posted: Mon Aug 08, 2022 7:58 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
Pascal's wager. 4:1 odds for that, who knows the odds for losing a WBX. A trip or two to get a minor part? or put it off and have the risk go to zero. Easy choice. There isn't anything I need equal to value of an engine swap.
Duncan |
|
| Back to top |
|
|
vanis13
Samba Member
Joined: August 15, 2010
Posts: 3100
Location: ABQ NM USA.... Except when not
|
| Posted: Mon Aug 08, 2022 8:06 am Post subject: Re: OK to run without coolant pressure cap? |
|
|
| DuncanS wrote: |
Pascal's wager. 4:1 odds for that, who knows the odds for losing a WBX. A trip or two to get a minor part? or put it off and have the risk go to zero. Easy choice. There isn't anything I need equal to value of an engine swap.
Duncan |
Not really the same. One could make the case you are at less risk running a open system than a closed system that can have a sudden catastrophic failure.
But if you got time, not using it is almost always less impactful (unless, like, you are under a tree that is about to fall)
_________________
83.5 Westy with Subaru 2.5, 4 spd manual, center seat, COLD A/C on 134a!, Winter camp heated with an Espar B4 gasoline furnace
www.SuperVanagon.com - some stuff I make |
|
| Back to top |
|
|
|
