RS Venture GT losing coolant

[Mooseman]

Related to RS Venture GT takes forever to warm up, now I find myself losing coolant. To recap, it had low coolant with no obvious leak, replaced the thermostat, refilled and it idles fine and gets up to temp and pressure. I also installed a temp gauge and bled the system of air (had it pointing nose up while running). Idled it up to 90c and nothing leaking. Take it out on a rip and it's losing it out the overflow hose (it doesn't have an overflow container). I refill it to COLD level and put the hose into a 12oz/350ml bottle zip tied to the oil tank. Went on another rip and it filled the bottle and puked even more out. The temp hovers around 70c while riding with good snow.

I have read some threads of RS/RX/Apex that don't like having too much coolant in the tank and generally like staying below the cold line but mine goes way below this, not even the bottom of the tank or even the hose connections.

It runs fine and as far as I can tell it doesn't have any telltale signs of a blown head gasket however this sled is new to me just having bought it late last season. It shows no signs of overheating, no light, all it does is puke coolant out the overflow. Next will be to put a 1L bottle to catch the coolant.

Any ideas?

 

[steiner]

If you are not overheating and coolant is blowing out then that only points to pressure entering the cooling system. That can only come from one place, the cylinders. It may not smoke white or burn coolant if the gasket is broken in a way that it does not allow coolant into the cylinder but allows pressure out of the cylinder. Had this happen on my 02 Viper. Never overheated but puked coolant all day long.
A cylinder leak down test would tell you if the gasket is blown.

 

[Mooseman]

I was afraid somebody would say that . I do have a leakdown tester with an attachment for our tiny plugs. It had a track that had some pulled studs. The tunnel protector brackets at the front were loose and looked like they were re-riveted so the front heat exchanger could have been replaced. Maybe when the PO saw that it was blowing coolant, figured it might have a blown head gasket and traded it in (I bought it from an AC dealer). If you don't run it harder than an idle or just around the lot, it's fine so even the dealer could have been fooled.

Well, the season here has been crap anyway, trails just starting to open now around here, others staying closed due to some club insurance issues and other personal stuff getting in the way of me riding.

 

[steiner]

Don't get too discouraged. Do the leak down test. Then you will know for sure what you are dealing with.
I spent 2 nights and a day chasing my issue and I wished it was just the head gasket.

 

[Mooseman]

Yeah, been reading your thread on the Apex. Good quick work done on that.

I'll do the leakdown test later today. Also looking into finding a test kit to detect exhaust gases in the coolant tank as further confirmation.

The stars are just not aligned for me this season. My mom was in the hospital in the fall, which prevented me from working on the sled, and was re-admitted last month during our trip to Florida. She passed away suddenly last Thurs. My boys are all here and we would have liked to ride together but it just isn't happening. Would have been good for us. And my son's Nytro is also acting up with TORS.

Thanks for the encouragement and help.

 

[steiner]

Sorry to hear about your mom.

 

[YukonMP]

x2

 

[Mooseman]

Finally got the time to look into this and it's not good. Did a combustion gas test in the coolant and I got nothing. That's the only good news. Then did a leakdown test. From mag to clutch:
67/80 84%
68/80 85%
15/80 19%

So obviously that cylinder is in trouble and noise was coming out of the intake. Never got any bubbles in the coolant.

Compression test:
192.5 psi
198.5 psi
179.5 psi

Manual says minimum acceptable is 209 psi but I did it on a cold engine so as to not gall the plug threads removing them hot. Maximum allowable between cylinders is 14.5 psi.

The plugs also tell the same story.


When I was doing the exhaust gas test, I zip tied the throttle to hold it at a steady 2000 rpm and it would hiccup once in a while. Idle is also irregular.

So my season is done or I run it as-is since I'll likely have to rebuild or replace it. I don't have a spare sled anymore and don't have the time or energy to pull the engine right now.

 

[74Nitro]

I have seen examples in years past where no leakdown tester will show the problem. Only the machine running will build enough pressure to cause it in some cases. I think the machine was ran without coolant at one time just long enough to cause a head gasket issue.

 

[Mooseman]

I'm back with this one with my resolution and didn't want to leave this thread hanging. I wound up taking the head off, resurfacing it, lapping all the valves and adjusting clearance. The head gasket didn't give a clue as to what was going on as far as I could see and figure it acted as a one way valve allowing combustion gases into a coolant passage but not letting coolant into the combustion chamber. There was some low spots in between the cylinders. I sanded down the head surface using emery cloth on a sheet of glass.

Took it out today and really romped on it duplicating the conditions that caused the puking coolant. Level is good and none in my catch bottle. Temperature held nice barely ever going above 70c unless I'm stopped.

As a side note, all my valve clearances were too tight. Had to buy a full kit of valve shims (expensive little buggers) to get them all within spec. Engine was super clean inside so maintenance was not an issue here.

Thanks all for pointing me in the right direction.