cooling system troubleshooting

[greg lousy]

I'm getting there

I've got everything running well except for a coolant issue. The engine (81 1.6 NA) sounds good, starts right up, then after about 5 minutes, with the engine at operating temp., I start rapidly losing coolant out of the top of the reservoir.
My first thought (fear) was that it was getting engine compression - I just did the head gasket twice, I have a new/reman head, so I was worried about a crack in the block (its not warped). I ran it cold for 30 seconds like I read about here - no issue. Then I bought a test kit from napa that detects combustion gases coming through coolant - negative (one of the best moments in this saga so far) - I was not, however, able to test at the moment of overflow, as it happens so fast that coolant bubbles up and gets into the test kit.
question 1 - should I still be worried about the block or can I exhale?

2 - I'm about to explore my cooling system. I'm posting in case the problem is clear to anyone, because its still a mystery to me
cooling system info -
almost no coolant comes through the little breather hose from the radiator, but it doesn't appear clogged because I can blow air through it (through the radiator and out the reservoir). The water pump impeller is not loose - I tested it when I was doing the belts (also it seems to be basically circulating coolant - heater hoses get hot quickly etc)
Its also not obviously leaking. - evidence of some kind of corrosion somewhere (particles in coolant).
- also, this is a WVO conversion, so I've got lines teed in to the heater hose going every which way, though I've messed with this system a lot before this and never had anything like this happen - even with unprimed lines, or lines with leaks.
T-stat somewhat new
No part of the system appears to leak

... also, i can't contribute too much knowledge here yet, but if anyone wants to borrow this combustion gas test kit for the cost of shipping, let me know - its pretty cool (makes you feel like a chemist)
give me a week or two though, may test again

as always - thanks

[TylerDurden]

I wouldn't rule out the head gasket yet.

It also seems the overflow occurs at the point the thermostat opens. Maybe pump pressure is getting in the return line somewhere.

If you can post a diagram of the WVO plumbing, that might help.

[82vdub]

If you have low flow coming from the small line from the top of the radiator, I would concentrate on that line first. If there's no or little flow, then any air that's in the coolant must "burp" from the lower suction hose coming from the overflow jug. This causes surges and pushes coolant out of the cap. I had this very issue on my old winter Jetta, until I resolved the blockage in the line. If your line has the little plug in the end of it with a small oriface close by the coolant overflow jug, cut it out. You may be able to blow air through the line, but if somethings in the line and you blow it out, when coolant flows it will push it up against the small oriface. The oriface in that plug is very, very small. BTDT. I'd look into this first and get good coolant flow through this line. If not, this portion of the cooling system isn't functioning properly.

[the man 53]

does it detect diesel? I have only seen those for gas engines.

If you have no obstruction, I would shut down the WVO system just to trouble shoot. If that doesn't do it I suspect the water pump. If you didn't change it, it is probably bad.

[greg lousy]

The test kit works on diesel too - the indicator fluid is deep blue and will turn yellow if a combustion gasses are present in gas engines, green in diesels, which is a less drastic change but in my case there was absolutely no change in color.

If you can post a diagram of the WVO plumbing, that might help.

i am camera-less. The coolant loops for the WVO system are teed off the "to heater" hose, and back into the "from heater" hose. These lines are all currently blocked off to simplify the situation (I've got ball valves in them)

If your line has the little plug in the end of it with a small oriface close by the coolant overflow jug, cut it out. You may be able to blow air through the line, but if somethings in the line and you blow it out, when coolant flows it will push it up against the small oriface

My line has no plug, but I had the thought that something similar may be happening, maybe at the little nub on the radiator the breather hose connects to. I'm away for a few days, otherwise I would have tried sucking through the breather hose by now (I have 100% water in the system now)

When I get back I'm going to start with the breather hose. I figure I'll work from there, down through the radiator, and then to the water pump. Things seem fine until the point the T stat would open, and the breather hose doesn't breathe - things are definitely pointing to that particular coolant loop - I'll keep you posted

[TylerDurden]

The coolant loops for the WVO system are teed off the "to heater" hose, and back into the "from heater" hose.

Sounds like you have it in parallel with the heater loop, rather than in series.

I would go in series:
Block->WVO loop->cabin heater input->stock return lines.

Parallel will not easily flush out the air.

[greg lousy]

I disagree, for my vehicle at least. I've rerouted these coolant lines three times - I started out with parallel coolant loops on the advise of some WVO veterans, then I put it in series, thinking it was more simple, then changed back to parallel when the loop wasn't getting as much heat. I like having the flat plate heat exchanger on its own loop. This is the most important heating element in the WVO system, and having it on its own parallel loop keeps more hot coolant flowing through it. Also, on long trips, I can shut off or restrict the coolant line going to the heated fuel pick up in the veg tank, when the tank itself starts to heat up. So basically, i have more control. This line is kind of awkward in my system, as the coolant goes through a hose in hose, then up above a huge 40 gallon marine tank to the fuel pick up, so I wouldn't want to add to the resistance by putting the FPHE in the same line, especially in winter when I have the line to the cabin heater partially open as well. The line with all my heating elements would receive even less hot coolant.

[TylerDurden]

Any chance the small connections at the water pump got swapped? That could push a bit of coolant to the reservoir when the t-stat opens.

It's vital that the reservoir outlet has a path to the pump's middle inlet. Usually that connection is a tee on the bendy pipe that goes behind/under the oil filter.

[greg lousy]

I think I might be in the clear.

I sucked through the little breather hose and it was as clear as it was when I blew through it. I did some other testing, then I started the engine, but I left the little breather hose disconnected because I was wondering if air was actually getting sucked into the system through it. As I was watching the engine heat up, feeling parts of the system, etc. a funny thing happened - nothing. The cooling system appeared to be running flawlessly - radiator fan kicking on, no overflow. To top it all off, water started coming out of the little hose. I set the hose over the reservoir and waited in disbelief - 15 minutes - no problems. I killed the engine and tried blowing through the little connector nub on the coolant reservoir, and I could barely blow through it - poked through it with an allen wrench and dislodged a piece of soft silicon type stuff.
unbelievable - of course the problem would be in the one inch of the cooling system i had not checked.

I'm not throwing confetti just yet - do some driving - then confetti time, but things are looking good.

thanks guys - I'm not sure if I would have been looking in that area so thoroughly if it wasn't for your help.

side note - the 50 bucks I was reluctant to spend on the head gasket leak detector kit is looking like some of the best money I've spent on this project so far (offer still stands)

[TylerDurden]

Sounds promising, keep us posted.

[CarlosA]

I pulled apart a waterpump today to check it out, it had a bunch of orange RTV oozed over inside from the previous owners assembly job.

Most of it wasnt even sticking to the metal anymore, i`m sure plenty of it was inside the engine and everywhere else.

[TylerDurden]

This discussion comes at a good time for me... I fired-up the '91 ECO for the first time yesterday. (I was slightly shocked it actually ran.)

The restrictor was plugged entirely. I should have just checked it beforehand. The reservoir overflowed after ten minutes of running.

After drilling, coolant and air ran from the tube like any good engine. Good tip on pulling the hose off the rez; the ball-version makes it hard to see the outflow from the tube.

Unfortunately, after ten minutes the tube gave only air and the rez bubbled like a pot on full-boil.

Both heater hoses were hot and both radiator hoses were hot (170F, 140F), So I think the waterpump is working; but the end of the radiator furthest from the hoses was only about 100F.

I'm thinking a mostly plugged radiator, but I'll have to do a cold startup to check hose-pressure to rule out the head gasket.

[TylerDurden]

Update:

Cold-start with the cap on the rez does not pressurize the hoses after 1 min.

Spot-checking with the IR thermometer: after the heater hoses show 160F, the oil-filter reads 150F, the upper radiator hose starts to warm to 150F (near the radiator), the lower radiator hose warms to ~120F... but the radiator far-end (away from the hose fittings) measures 75F.

Methinks the radiator is plugged.

[coke]

Most cooling system issues I've encountered on MK2 cars is the radiator. I can't tell you how many times I mistook a blown head gasket for a radiator. Imagine my surprise after changing out the head gasket and having the same issue. I didn't make that mistake again.

[greg lousy]

there's a chance this little blockage in the little nub on the reservoir was my problem to begin with
head gaskets - 2
actual repair time - 10 seconds
live and learn