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Engine Lopes Then Dies

01-16-2008, 04:07 PM
:banghead: hello,new here and glad to find the site....we own a 98 venture with 125000+ on it.It has been a great van with no problems.I noticed the temp gage moving extremly from normal to 3/25 in a matter of 10 seconds about 6 months ago.I had the radiator flushed and it ran normally until the low coolant light started comming on about a week ago.sure enough it needed coolant.yesterday the light my wife pulls in the driveway and the idle was loping and it died.It is hard to restart and when it does it still lopes...when I give it gas it will stay reading the manual it tells me internal coolant loss and loping idle could be head gasket or cracked head:eek:how do I confirm this and tell which it is(gasket or cracked head)myself.....sorry for the long post and thanks for any input.

01-16-2008, 09:49 PM
I just got done doing head gaskets and intake gaskets on my daughters '02 Venture. According to a former GM mechanic friend of mine it is usually the back head (closest to firewall) and it usually starts leaking on the passenger side of that head.

I ran her van up on ramps before tearing it down and could visually see a small stream of water leaking out between the head and block on that corner. (front of engine, passenger side).

Not very scientific, but it worked for me.

Hope this helps.


01-17-2008, 04:58 AM
Thanks,I will do that.How much time did it take?Is this a job for a non mech and what should be checked while I have it open?

01-17-2008, 05:56 AM
I guess it depends on what you mean by non mechanic. I'm not a professional mechanic, but my dad was.. I have a good set of tools and a heated garage. I've sort of made cars my hobby.

If it is indeed head gaskets you'll need a set of metric tools including deep well sockets. To remove the intake and heads I found out you need to disconnect the exhaust pipe at the rear manifold so you can rotate the engine forward (after removing the front dogbones) for better access to the rear head.

I removed the heads (with exhaust manifolds still attached) and took them to a machine shop to have them cleaned up. If they've been hot enough to blow a gasket they will be warped. You will also need to install new head bolts as they are a one time deal.

I got a good deal on a head overhaul gasket set on ebay from Reliant gasket. Included every single thing to do the job including some updated intake gaskets that have a little metal inserts (to prevent overtorquing maybe?)

This is also the time to change spark plugs and the thermostat as they are way hard to get at otherwise.

It took me a long Saturday tearing down and a couple of long evenings reassembling. (I'm not particularly fast)

You should also have a chiltons or haynes book handy although they are sometimes of limited value.


01-17-2008, 04:45 PM
I would also pressure check the radiator, flush or replace as necessary, and definitely replace the timing belt and water pump. The water pump usually gets stressed as well as most other coolant-carrying devices/hoses when the head or possibly the intake gasket fails. My water pump went on my 97 one month after my intake/head repair was done.

01-20-2008, 06:28 PM
these are symptoms of a blown head gasket but also it could be alot of other less drastic things too. a bad radiator cap will let the cooling system lose coolant, a bad tps will make the idle go lopy , but when you give it gas it will smooth out. have you had the codes pulled on it ? if so what codes? a head gasket leak will usually produce white smoke from the exhaust and steam coming out exhaust so if you put your bare hand up to the tailpipe it will burn you any closer than 3" from the tailpipe.

01-22-2008, 03:42 AM
thanks for the input.I have looked over the motor from underneath and I do not see any leaks.Is there always an external fluid leak?The oil level remains constant.....As for the codes.I have no light on. I guess I need to try to pull some...It would be great if it turned out to be the radiator cap or tps..tearing down the top of the motor myself is very scary to me...I have no doubt I can take it apart but putting all the pieces back together correctly is another thing..LOL

01-22-2008, 09:31 AM
go get the cooling system pressure checked if you have an autozone near you they will loan you a pressure pump you put it on where the radiator cap goes after the radiator cools down so you don't get burned . pump it up a little over the cap rating your cap should be 16 pound cap so pump it up to 20 pounds and let it sit if the pressure starts to fall then you have a leak .it can be anything on the cooling system and if you have a rear heater check out the heater hoses going to the back also for leaks.if you can't find an external leak then you have an internal leak. this can be a intake gasket or a head gasket. and it could be a head that has a crack in it. is the exhaust hot by hot i mean will it burn your hand if you put it 2" from the tailpipe with it running. can you smell coolant at the tailpipe? be sure to have a good light when looking for the leak. and look around the top of the motor real good paying close attention to the intakes. the grey plastic on top of the motor will come off by removing the complete oil cap by complete i mean the part the oil cap screws on will unscrew sure to wipe around it good so no trash falls into the valve you have any creamy looking stuff in the top of the oil cap? when you give it a little gas to make it run does it miss?

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