T-apex overheats on boost

[bigrhett]

OK, here's the deal:

2007 Apex with boondocker turbo. 10:1 pistons and Carillo Rods. Attitude box, stock Maverick track, 60/40 mix of antifreeze. No side vents. AFR's look good when on boost.

If I let it idle it will get hot enough to turn on the fan and the overheat engine light (which is normal I hear). No big deal as I can just start moving and get it to cool down. I can drive on the trail or even on the small hills with a quick burst of boost and it's no problem.

However, when I get into the boost (16-17psi) for a good pull (over 30 seconds) and I turn down the hill, I get the yellow hot engine light and get a steam bath of antifreeze vapor coming out under the hood. If I pull off the plastic cover then I can see that it's bubbling into the overflow bottle and the cap is WAY too hot to take off for 5-10 minutes.

Here's what I'm wondering:

1. Is the turbo physically heating the coolant lines to the point of boiling? (will some side venting and more heat tape help?)
2. Is there a problem with the head gasket?
3. Will a rear heat exchanger fix it?
4. Could the radiator cap be busted and not keeping the pressure right?
5. Where else do I need to be looking?

Where are the likely culprits and which fixes or tests should be done first? An unacceptable answer is "Just turn down the boost"

Thanks

 

[boosted metal]

have you pressure tested the coolant system off the rad cap for leaks/ loss of pressure.stock tunnel w stock heatexchangers?what was the outside air temp when overheating.whatis your air/fuel reading at wot?

 

[robertyoke]

could be a restriction some place in the cooling system or weird thing like a spun water pump impeller but my guess would be......

the head gask may be leaking under pressure. sometimes you will see coolant in the oil or oil in the coolant but not all the time.
i would do a compression test and see how close the cylinders are if they vary more than 10% i would start there.......my $.02

 

[bigrhett]

-Stock tunnel, stock exchangers
-20 degrees F, maybe a foot of powder on a decent base when climbing
-running about 12:1 on the AFR at WOT
-I don't have gray goo in the oil and don't see oil in the antifreeze...
-the heat exchangers get hot all the way around the sled, so at least some fluid is circulating.

I will pressure test the cooling system and do a compression test on the cylinders next.

 

[zebiraross]

I think your looking in the right spots. Like others have said. Just replace the radiator cap so that's not a issue. Do a compression check and you can find if it's a hg. If it's only happening under boost I would first check there. Like Robertyoke said it could be a spun water pump bearing. I had a turbo 700 polaris that was doing the same thing as yours. I thought it was a base gasket. Replaced several times, still nothing. Replaced radiator caps, everything. Finally found out it was the water pump impeler after about 2 weeks

 

[snowy1]

I suspect you are blowing by the head gasket under boost, did you put hd head bolts.

 

[SPOOLED]

check the thermostat take it out and see if it opens when you heat it up, put it in boiling water make sure that the water temp matches the the temp of the tstat eliminate the simple things first.

 

[BigFish BC]

have you recently changed the coolant or did you do the motor work this year sounds like its got air lock in the system seen this a few times.have to raise the rear of the sled up high & let it idle with rad cap off till it stops bubbling.

 

[snowy1]

he said everything is getting hot so it must be circulating properly, if its only doing it under boost I think its the head gasket.

 

[Linc]

My vote is head gasket,,,sorry.

 

[Transporter]

I dont see my sled overheating when idiling, mabye I never let it idle long enough.If it was headgaskets wouldnt it just puke antifreeze?Why would the temp light be coming on?

 

[WesG]

Headgasket

Sounds like the headgasket to me too. It will loose circulation when it gets combustion gases into the coolant. If it is blowing out enough to fill the overflow bottle and spray out in one run, the gasket is in bad need of replacement. They are notorious for leaking under boost pressure but not while idling or at low boost settings. Mine did not show black crap in the coolant jug for quite awhile, but it did show up after a time.

 

[bigrhett]

If it was headgaskets wouldnt it just puke antifreeze?Why would the temp light be coming on?

That's a good question...but if enough air gets in the coolant, then it would get hot I suppose as it isn't dissipating the heat...

-Don't know if the studs are heavy duty. I bought the sled already assembled, but not dialed in...the prior owner rode it once and scared himself so I got a great deal I just called the shop that installed the kit and they didn't put heavy duty studs.

-Are heavy duty studs necessary? (or is that like asking which oil is better?)

-Is there a special procedure to be followed on a head gasket besides what's in the manual?

 

[boosted metal]

pressure test it at the the coolant system at the cap, then you will know if there is a drop in psi or you will see a coolant leak, head gasket

 

[BigFish BC]

he said everything is getting hot so it must be circulating properly, if its only doing it under boost I think its the head gasket.

when my head gasket went it would just push coolant out the overflow never overheated at all strange.a leak down test will tell you if its the head gasket.

 

[Sapling-Thrasher]

Head Gasket

Mine would leak under boost. Low boost ran fine even on long pulls I never got it hot enough to turn the light and fan on it would just push coolant out into the catch tank.

 

[snowy1]

if it turns out to be the head gasket which I suspect it is, you need hd studs, then clean head and block surface with acetone need a clean dry surface. do not touch surface of gasket with fingers you need it to be oil free. tork in proper sequence, 10 lbs then 20 lbs. then 28 lbs. on the last tork turn back 1/4 and retork to 28lbs. in one motoin as you go through the proper sequence.

 

[bigrhett]

if it turns out to be the head gasket which I suspect it is, you need hd studs, then clean head and block surface with acetone need a clean dry surface. do not touch surface of gasket with fingers you need it to be oil free. tork in proper sequence, 10 lbs then 20 lbs. then 28 lbs. on the last tork turn back 1/4 and retork to 28lbs. in one motoin as you go through the proper sequence.

Thanks for the tips. Should I have the head checked for warpage while I'm at it? It's only got about 600 miles on the engine with 200 of them on the boost. In fact, now that I ask the question, it would be stupid to not have it checked after going through all the work.

Any recommendations on where to get some hd studs?

 

[snowy1]

call paul at Impusle he shoud be able to get you some or tell you were to get them. www.Impulseturbo.com

 

[capen4]

one more thing to check for
Check for a small hole in CAC system sometimes with the trucks I work on if the Charge air system has a small leak small enough you might not feel any boost loose but the charge air pressure is down. this with cause the burn to be lacking and cause higher temps in the cyclinder.