I know where this is headed....I just need some other opinions. Its weird if anything and not conclusive otherwise the heads would be off...

Installed a new hi-flow water pump 2 mts ago. Ever since then there has been a slow minimal coolant loss. Now that temps are going up and the engine is spending more time at the upper end of the temp scale..the loss has increased.

Symptoms:

usually does not loose coolant until driven at freeway speeds for more than 30 minutes. Then it looses enough to overheat (into 240 area).

no external leakage that I can find as of yet.

No water/oil mixing anywhere.

spark plugs all look the same...no clean or washed plugs.

system holds pressure for hours hot or cold.

short hop, city driving takes longer for coolant to disappear. High rpm seems to accelerate the loss.

water flows freely thru radiator.

No misfire when running. Its rough at cold start but thats normal for this engine. Smooths out as it warms.

I did notice during one incident that the full radiator would not suck down the water when rpm increased. Like the lower hose was collapsed, but it was not. New pump and I can see the flow at idle and above.

I have a venting system installed so air can be bled off at the top most heater hose...(high point) also water can be added there to pressurize the system with the cap on.

The question is...

where is the coolant going and how/why is it going?

I have tried some aluma-seal stop leak

.....it did nothing except liberate $12 from my pocket.

ANY thoughts on this before I get the tools out and order gaskets?

Ideas? I'm lost on this. can an intake gasket do this? or does this spell h-e-a-d gasket ?

 

head gasket, sorry.
Same symptoms you had threw me off for awhile.

Eventually it built up enough crankcase pressure in the coolant system that once I pulled in the auto parts store to get one of those system checker deals the lower radiator hose blew off once the car was shut off.

Normal driving ran good temps til as you said above....

 

external coolant leak that is evaporating before hitting the ground. look in the hardest to see places such as the back side of the radiator, firewall under heater hoses for a water track.

 

Pressure test and block test. Sorry buddy

 

holds pressure hot or cold....holds for hours.

no loss while sitting under pressure. BUT, no washed spark plugs either.


I know with the L98 the most likely thing IS the head gasket....and if so, I'm goinjg to do some upgrades while the heads are off.
Just want to be damn sure before pulling the heads since this will easily break me and my disabled fixed income budget...big time! Tomorrow is the last chance to find a tiny external leak...then if I can't, its going to be written off as internal gaskets and get parked until I can deal with it...what a PITFA.

 

I had a similiar problem. if you send your oil out for analysis, you may find antifreeze in the oil.

I never fixed mine, but I did spin a bearing at 120,000 miles, and junked the car.

 

Sorry to hear that. I have a set of intake and head gaskets you can have they are chepo Rolo gaskets tho.

 

If you know someone with an emissions exhaust sniffer, you can wave it over the radiator with the cap off to detect hydrocarbons in your antifeeze. I have never done this, but I hear that it works. A great place for mystery leaks and/or pressure loss is your heater control valve. I do have experience with this one.

 

I think we have a WINNER !

red89c4

enjoy your trip to the Bahamas! ( yeah right) my gratitude will have to suffice.

Fri nite I decided one last time to try to locate some leak or some point of discharge since I was unable to prove that it was internal.

I placed painting masking paper under the engine and pressurized the system and went to sleep.
This morning I went out to see and sure enough the pressure has bled down. That was expected...but the couple of tablespoons worth of water on the piece of cardboard (on the paper) directly under the a/c compressor where that abortion of heater hoses T into each other for the pump, had a wet fitting. The aluminum tubing from the engine oil heater/cooler oil filter had a pin hole up inside the rubber where the hose slid over...almost covering the hole but not sealing it. It was/is MINOR>....very very minor. BUT, it seems that with sustained rpm, and the high flow pump, and high temps that it would weap a little water that was being vaporized under the car as it traveled.
Supporting evidence is little spots on the tail/bumper where the draft sucks things from under the car then slams it up and against the rear end of the car..in the negetive pressure zone that sucks at race cars the faster they go. Spots....I didn't even notice that until I started seeing that there was some sort of a very fine leak.
Repaired today and ran it up to 210 and held it to 3500 rpm for a little while...and idled it for 1/2 hour. Heats up and cools as it should, no sign of coolant loss as of yet. Tomorrow I'll do a more extensive test drive to see for SURE if thats fixed or not...

One thing that I DO know for sure...This engine is getting loose and I need to start planning for another. Not using oil...just loose. Its time to start looking at short blocks and gathering pieces for a build so I can just do a swap in a few months. I do not want to run this one 'till it drops...

I'll post tomorrow about the results. So far, full of clear water, no bubbles, no loss, so I'm hopeful.

 

Something else worth looking at - just above the oil cooler hoses at the #7 cylinder. That's a common place for an external head gasket leak. Coolant could be leaking externally and burning off on the block.

 

Easy to use and still less than $30 from a vendor near by ...
While you may not like what it tells you, early detection can
mean the difference between routine maintenance and an
engine replacement.

.

 

weak radiator cap

 

Boy did you dodge the infamous L98 Headgasket bullet!!

Your symptoms are telltale of it. Leaks being temp sensitive and all.
Hope we didnt panic ya

 

yessir...I was loosin sleep over that and just knew what the problem would end up being.

Thing was, with me, maybe its my background in engineering and the world that I worked in for 35 yrs where stressful situations/problems demanded fast answers and you had to PROVE your theory...think it through. Apply your knowlege, your experience and use the odds. Make a decision based on all that. Just be right, thats all.

So,
it just didn't add up. Many symptoms were there but not the last one or 2 necessary to say 'head gasket' with 100% certainty.
There was no evidence of water IN a combustion chamber. Then there was no bubbling in the radiator...(took stat out and topped off and revved to observe the flow).

BTW...FSM says to remove serp belt, remove the cap, rev motor and watch coolant level. If it moves its a gasket. It should not move since there is no pump involved without the belt....with engine revving up & down.

It was aggrevating because I just did the #7 dance 3 yrs ago. Maybe 50K on the motor since then and the maint has been excessive if anything.

And there was nothing in recent history to ruin a healthy head gasket. No over heating, no dry operation, no abusive operation. Not much anyways...
I changed water pumps because the old one wore out the shaft bearing....wasn't leaking a drop yet. Just got loose enough to make noise so it got changed and upgraded to a hi-flow. The first time it had a noticable loss of coolant was just days after the pump swap. It started out every couple weeks some water missing...then days...now it used water in hours. Steadily got worse since the pump swap.

Still, I could not PROVE that it was a head gasket.

OAM, gets points as well...
The old cap was a safety cap with the relief lever....that was allowing some premature venting before 16 lbs. Guess it went soft...seal looked ok, spring must have gotten weak. Stant safety cap.

After discovering the very tiny leak in the tubing, I also noticed the radiator venting off minor pressure after shut down and temps were nowhere near hot enough (190) to justify venting to the expansion tank. So I took the shroud off and cut a small section away to allow for the HD cap that came with the big radiator to fit and installed that. Got 2-3 handfuls of leaves outta there as well...

I've been purposely running the temps up and then going thru a cool down exercise....(steady cruise speed, fans on, rpm up with no prolonged idle and it'll now act just as it should and drop from 220 back down to 180s after a few minutes of moving. AIR is everything.....30 mph is better than the sucker fan running anytime. I try to keep it around 195 but thats difficult in the Gulf coast with your a/c running this time of year. Its just gonna get hot as it sits at stop lites and if all is well, it will/should cool down as you move again. Just the nature of the beast.

Anyway...
Went and looked this morning half expecting to see SOME loss of coolant just from expansion yesterday..but it was full to the top.
So I'm thankful...as I told someone else, THAT would have been THE straw......

This whole incident did get my attention and refreshed the idea of getting another block to start building a fresh motor. This one has served me well and with a valve job it would probably go another 50-100k. Its got over 170k now, and much of that was in the dessert at higher than usual temps. So its getting a little loose. No oil burning yet, just loose. Time to start thinking of what I want next time instead of having to settle because it scattered at a bad time. Trying to decide if I want to go with more inches....like 400 sbc, or forced induction of some sort, or maybe a forged bottom end and juice it....lots of options these days.
Just glad that 'ol #7 didn't decide to choose for me. !

 

I want to ad to your interesting post. I recently swaped out my radiator, hoses, radiator cap, and went to a 160 degree themostat. I also had a large amount of leaves and crap stuck between the radiator and A/C condensor. My temps went from 220-230 at high speeds to 180-210 max. I could not run my A/C before doing this work. I never thought about all the crap jammed in there ? My radiator had a small leak so it had to go. I live in the desert and its over 100 degres most of the time now. I was running 140mph and my coolant temp stayed 210. Your post is great thanks for the info.