Losing coolant, any advice? (other than drink more beer ;) )

[C 4]

Hi Guy’s, a little advice/thoughts please,

93-C4, approx 80k miles, no major mods.

A little while ago the thermostat jammed partially shut and she overheated, not the clouds of smoke and steam type, just the gauge went high and the warning light came on and it blew some coolant out of the expansion tank.

Still waiting on a new stat, so running without one at the moment, also haven’t corrected the anti-freeze/water mix (50/50) yet, just topped up with plain water.

Problem: It’s loosing coolant, but I can’t find a leak, nor is it blowing any white smoke out of the exhaust, nor can I see any water contamination in the oil (nothing on the dipstick, the level isn’t rising, no gunge on the oil filler).

I’m competent enough on run of the mill engine/mechanics and my instinct is it needs a hydro-carbon test on the coolant and/or a compression/leak down test to check for head gasket(s). Having said that, I know absolutely zero specific about the vette engines and cooling system, so I was wondering if there are any peculiarities with this engine that could be connected to disappearing coolant.

I’m not in a good position (miles from nowhere and hundreds of miles from anyone who knows vettes!), so getting the tests done won’t be easy and ripping the heads off without having all the new gaskets etc is out.

Any suggestions for a course of investigation?, I’ve read that the intake manifold can be a source of coolant loss, should I take this off first or would a leak there have produced an under-car puddle that I would have noticed!.

Also, just wondering, I’ve read that the coolant flow is reversed in these engines. Would running without a stat have some kind of adverse effect where coolant is lost and/or would the low SG of the coolant mix cause any related (loss) problems… I’m thinking along the lines here that anti-freeze allows the coolant to run hotter.

Any/all thoughts appreciated, just try not to frighten me too much.

Thanks.

 

[Jsup]

Simple, find the leak and fix it.....

 

[Jsup]

Seriously, is there water in the oil or oil in the water. I'd be looking at the head gasket.

You didn't say how much you're loosing.

Smoke out of the tailpipe?

Pressure check the cooling system. Probably the first thing to do.

You said you had some general automotive knowledge as to testing the antifreeze and doing a leak down test. That is basically what you have to do. There is nothing really special about this motor, it's a run of the mill small block. Same as a truck or anything else.

The LT1 is reverse cooling, but that's about it when it comes to troubleshooting this problem.

 

[mrvette]

Seriously, is there water in the oil or oil in the water. I'd be looking at the head gasket.

You didn't say how much you're loosing.

Smoke out of the tailpipe?

Did you pressure check the cooling system. Probably the first thing to do.

I have a LT1 heavily modded intake on my L98 engine....long story, but it runs like a raped ape...and in doing that switch last winter, I spliced in a a/c fitting sweated into a 1/2 inch copper plumbing tee, so I can pressurize the cooling system even when i'ts full of water, regardless of engine temp.....I just use my airhose through a hose barb to R12 fitting on the gauges charge/yellow hose, and connect the lo side/red hose to the fitting on the heater hose....this way I just open the valve to 15-16 whatever lbs pressure and wait for the cap to let it off, making sure the rad is full up top....

then wait.....it better hold for some 30 minits or so....if not, there IS a leak....

hoses, radiator, HEATER CORE (can be looped out to eliminate it) and water pump are all obvious cheep solutions without getting all static about it....

after that, look for drips on the front of engine block, or maybe the freeze plugs in sides down lo, or out back where the fly/flex plate is....dripping out the tranny case down lo....

when the engine is hot, the leaks are under pressure alright but HOT, when cold and under pressure, the suckers leak more....TYPICALLY.....

done this many times, this time I got lazy and left the fitting on the car, permanently....

:bonkers::yahoo::goodnight:

 

[turtlevette]

it's a blown head gasket. I've already been through this twice with the L98 heads. The LT-1 heads are similar in robustness ie. not very robust.

It starts off with loss of coolant. Then evolves to puffs of smoke on startup. Then finally engine running rough.

 

[redvetracr]

you need to do a cooling system pressure check...I think Stant makes a tester...borrow one or look on ebay.

 

[mrvette]

it's a blown head gasket. I've already been through this twice with the L98 heads. The LT-1 heads are similar in robustness ie. not very robust.

It starts off with loss of coolant. Then evolves to puffs of smoke on startup. Then finally engine running rough.

DAMN, I agree with TV on something, :shocking: but so I thought so also once on this install of the L98 heads....but with the Felpro gaskets I was/have been proven rong, it was the freeking WATER pump bolts, on the pass side, so I had to loosen the a/c comp bracket off the serp drive, drop it forward, to get to the secondary set of bolt/stud nuts on the pump itself....PIA, but better than another set of gaskets...so far so good....

:rain:

 

[Twin_Turbo]

The L98 and LT1 heads have a notoriously thin deck, they will warp rather quickly when overheated.

 

[C 4]

Many thanks guy’s, some interesting food for thought in those replies, especially plumbing in a semi or permanent pressure test point… I have a multitude of fittings and gauges knocking around the garage that should do that job. BTW MrVette, I like the description “raped ape” :wink:, I take it such abused primates can move a tad swiftly? (don’t want to enquire how you’d know though :amazed: ).

Bottom line seems to be head gasket(s), anything unusual with changing these?. I assume the heads will need re-surfacing and I guess I’ll need to get on order new rocker cover and intake/exhaust gaskets as well as the obvious head gaskets… anything else I should have to hand or worth changing while I’m at it?

 

[turtlevette]

The L98 and LT1 heads have a notoriously thin deck, they will warp rather quickly when overheated.

i wish i had taken pictures as the mill took material off. the whole head is concave with the lowest spot between the middle 2 chambers right between the 2 fire rings. You actually can see the fire ring indents. Takes about 10-12 thous to get them flat again.

I'd never put a used aluminum head back on a car without having it milled flat first. I'm convinced they develop low spots even without overheating.

Almost makes me want to go back to all iron.

 

[mrvette]

When first building this engine 12 years ago, I put on old thick iron heads....then found out a couple years later that Edel had a decent affordable set out....put them on, supposedly a nice thick casting got hot ONCE, and they blew the #8 cyl....header leaking water and oozing out the head/block surface...no where to go with THAT diagnosis....
went to the same iron heads....had the gaskets, figgered hell with it, fastest way on the road....

found a cheep enough set of L98 #113 heads....like 150 bux at the door, got my head shop to work them up....on the car longer than the Edel heads at this point....Ralph did the steel bar on the head trick with the feeler gauge when bringing them in...straight...asked him to take a couple cleanup runs anyway....

so this is the 3rd actual set on the engine, and 4th install....

dunno the Edel extra thickness did anything much, seems to be enough ARP bolt count in there from Chebby anyway....

the 'Raped Ape' is a VERY old reference, dating back some pushing 50 years now....grade school.....:hissyfit::beer:

 

[gkz]

The heads already have small enough chambers; how much can you mill off the surface and still run pump gas? Don't LT1's run flat-tops?

 

[mrvette]

The heads already have small enough chambers; how much can you mill off the surface and still run pump gas? Don't LT1's run flat-tops?

I don't remember, some 18? years ago, for a boat project I had a bought a kid's wrecked '87 vette engine, got the whole thing, from fans to tranny, missed nothing, traded a guy for the '88 compressor bracket....the drives are on my car now....I don't remember the piston tops from that engine....I did not use it, bought a lighter boat, too much for tow car....I dunno about LT1 engines at all....I can't imagine too much taken off these L98 heads I have now...the others could have been scalped but good and not ever affected comp ratio....
friggin bath tubs for chambers....the engine I built is TRW double eyebrow slugs, flat tops, 355 ci.....pretty much stock as a stove...

:shocking:

 

[turtlevette]

The heads already have small enough chambers; how much can you mill off the surface and still run pump gas? Don't LT1's run flat-tops?

Use the graphite coated ZZ4 head gasket from the dealer when you go back. Its about 0.010 thicker than most gaskets. Your compression will stay about the same.

 

[C 4]

Hi guy's,

Sorry it's taken sometime to get back... only just had time to fix the car.

Just to close the thread, it turned out to be the water pump, the bearing had collapsed. Changed it and no more problems.

I've done a few miles since and touch wood no signs that opti was damaged.

Thanks for all the help and tips.

 

[turtlevette]

Hi guy's,

Sorry it's taken sometime to get back... only just had time to fix the car.

Just to close the thread, it turned out to be the water pump, the bearing had collapsed. Changed it and no more problems.

I've done a few miles since and touch wood no signs that opti was damaged.

Thanks for all the help and tips.

I'm glad you didn't tear the heads off. Sorry for leading you down the wrong path but you said it was recently overheated and you couldn't find any leaks. I guess you weren't looking hard enough.

I'm glad it was only the water pump.

 

[C 4]

I'm glad you didn't tear the heads off. Sorry for leading you down the wrong path but you said it was recently overheated and you couldn't find any leaks. I guess you weren't looking hard enough.

I'm glad it was only the water pump.

Absolutely no problem Turtle. It had overheated and I never did find the leak prior to ripping the pump off and I was thinking head gasket(s).

Appreciate all input, it all gets the old grey matter working and makes you feel less on your own!

Thanks again.

 

[TimAT]

Bottom line seems to be head gasket(s), anything unusual with changing these?. I assume the heads will need re-surfacing and I guess I’ll need to get on order new rocker cover and intake/exhaust gaskets as well as the obvious head gaskets… anything else I should have to hand or worth changing while I’m at it?

Have some thread sealant on hand too. All the head bolts need a coat on the threads. They go into water and will seep. I'm guessing your heads are aluminum? If so then you also need to make sure the washers on the head bolts are lubed so they don't gall. Only thing I can think of. (there's probably something else?)