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1983 Vanagon watercooled, too much pressure in coolant bottle?

For 6 months I've been getting a lot of pressure in my main coolant reservoir, the one on the left rear side of the engine compartment. Normally this would be from a blown head gasket, but in this case I'm not sure and I'd like some opinions. Here are some things I've checked:

compression test: 140-150 (was 110 on left side until 2 months ago and mysteriously came up to normal...and gas milleage improved noticiably). Engine has 10,000 miles on rebuild, this compression reading was low on the left side long before this pressure problem.

vacuum gauge test: (takeoff from hose to fuel pressure regulator): Idle: 5 "hg (cold) to 8"hg (warm).........this is real low. When snapping the throttle open and then letting it go, vacuum reading goes below

5" and then up to 18" max. Increasing RPM: vacuum reading is higher than idle reading and increases as RPM increases, but max is 18". Removing plug wires one cyl at a time, Vacuum reading changes about the same for each cylinder, same goes for RPM changes, can't really tell if one cylinder is not carrying it's load.

Idle: vacuum gauge needle varies about 1/2", not too bad...idle is a bit shaky but not horrible.

No steam coming out of exhaust pipe, some water/coolant usage but not very much. Just so much pressure in coolant resevoir that the level is always low and the low level light is blinking all the time (unless I release the pressure at the resevoir cap). Because of the excess pressure the coolant from the overflow bottle(behind the liscence plate) is blocked, and the overflow bottle is bulging and getting developing weak spots.

I'm trying to figure out if these symptoms would point towards some other source of the pressure, such as the metal sealing ring on top of the cylinders(between the cylinder and the cylinder head). Does anyone have any direct experience with this kind of problem...I'd like to hear some opinions, or troubleshooting suggestions.

John

Reply to
jbclem1
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1- have you tried a new cap 2-are you bleeding the system correctly? I did it by running the engine "cold" at 3000rpm and adding coolant until the bottle was full. Also opened the bleed valve on the engine. I added coolant until the bottle was full and just before the coolant would start over flowing due to the engine getting hot. Then bleed from the radiator plug. 3- if you still have the problem, then sorry to say then you got internal problems such as the gaskets between the cylinder and head, or a crack in the head.

Regards

(warm).........this is real

Reply to
Woodchuck

other source of the pressure, such as the metal sealing ring on top of the cylinders(between the cylinder and the cylinder head).>>>>>>

Wasserboxer engines are famous and reknowned for having problems with coolant leakage that gets worst and worst until the engine will not start, including steam eventually in the exhaust.

The problem is the reactive metals between the heads the seals from the cast aluminum. Even if fixed it will happen again.

The most permanent fix is heads that have been remachined with (been a while since I read the articles about it and I had a family member with this problem, why I know) I believe, the retrofit shops use a different aluminum welded and machined to the modified heads.

Coolant problems are the number 1 main problem with this vehicle every time.

Reply to
Sam

I guess I'll repeat the question again: Does anyone know how to distinguish(diagnose) between a cylinder head gasket that isn't leaking water and a cylinder sealing ring(spacer) or cylinder o-ring problem. What is happening is pressure (exhaust) is getting into the cooling system. There is no noticiable water leaking/usage, but lots of pressure getting into the coolant resevoir. I'm also trying to figure out which side this is coming from and standard tests are not showing anything that would point to a specific cylinder or cylinders.

John

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Reply to
jbclem1

OK I guess I wasn't clear on my previous answer. Sounds like whoever did your engine 10k ago didn't have the heads fly cut or whatever they call it. I took valve grinding compound and used a sleeve to dress up the sealing surface on the heads. On my 84 vanagon I had over pressurization. This is a very common problem on Vanagons. Then very quickly water started getting into the combustion chambers causing lots of noise on startup. It does not matter, O rings on the top sides of the sleeves or sealing rings between the head and sleeve, the heads must be removed to do either. But to be specific, it's the sealing rings between the head and sleeves that are leaking. The thing most people in the US notice first is water drips, that's caused by the head surface deterioting where the large rubber gasket is. The problem is more apparent in the winter when it's cold.

JoBo

(warm).........this is real

Reply to
Jo Bo

Jo Bo,

I don't see a previous message from you in this thread, did you use a different name(nick)?

With air-cooled engines it was smart to flycut cylinder heads, and I always used a cylinder and valve grinding compound to make sure the sealing surface was even and matching the cylinder. But I'm not sure that's necessary when you have a water-cooled engine with a metal sealing spacer. And the problem with air-coooled engines was that the heads would come loose and beat out the sealing surface in the cylinder head, or the exhaust gases escaping(when you had real loose heads) would cut little slots in the sealing surface. So you either flycut that head(which lead to many rebuilt heads that were flycut way past specs and gave you a compression ratio higher than you might want), or did the valve grinding compound routine. I don't think loose heads is a very common Vanagon problem, but you can't go wrong with a little dressing...realizing though that the dealer mechanics will throw away the water-cooled heads if there is any warpage or imperfection, and a really good machine shop that I used would only flycut these heads to .015 inch max.

I'm curious to know about the over pressurization you mentioned. What causes it, and what kind of noise does water getting into the combustion chamber make(is the noise sharp, dull, deep...when does it occur, when you let out the clutch, when you wind out the engine in a gear??).

I'm not getting any large water loss, or vapor coming out of the exhaust, just the pressure in coolant resevoir. I'm trying to figure out which side or cylinder that problem is coming from...this is a recent rebuild and I'd rather not do both sides if I can avoid it.

John

Reply to
jbclem1

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